Pierre MKOUNGA

Antibacterial, antibiofilm and anti-quorum sensing activities of 1,2,3,5-tetrazine derivatives linked to a benzothiazole moiety

Jean Paul Dzoyem, Joseph Tsemeugne, Boniface Pone Kamdem, Rostand Foyou Meupiap, Boris Arnaud Kuate, Pierre Mkounga et 2 autre(s)

bioRxiv (Cold Spring Harbor Laboratory)

Abstract A series of known tetrazine derivatives, containing benzothiazole scaffold, were prepared during the coupling reactions of selected diazotized 2-aminobenzo[d]thiazole derivatives with p-acetaminophen. The as-prepared compounds were characterized based on NMR and MS spectrometry. The antibacterial and anti-biofilm activities of the synthesized compounds were evaluated by microdilution method, whereas the anti-quorum sensing effect was carried out using assay for the inhibition of violacein formation. As a result, compounds 4a, 4b and 4c revealed minimum inhibitory concentrations and minimum bactericidal concentrations ranging from 8 to 128 µg/mL and from 32 to 256 µg/mL, respectively. Compounds 4a (52-86.5%), 4b (57.7-79.4%) and 4c (59.9-80.3%) prevented biofilm formation in all the four bacteria tested with percentages of inhibition more than 50%. The concentrations of 4a, 4b and 4c that inhibited 50% of violacein production were found to be 62.71, 28.56 and 107.45 µg/mL, respectively, thus attesting that these compounds possess anti-quorum sensing activity. Noteworthy, our previous investigation attested that these compounds are non-cytotoxic on the human mammalian cells Vero. This novel contribution demonstrates the antibacterial, antibiofilm and anti-quorum sensing activities of tetrazine-based benzothiazoles, which might be prospected as scaffolds for the discovery of efficient antibiotics with decreased risk of microbial drug resistance.

• #phenothiazines and benzothiazines synthesis and activities
• #antimicrobial agents and applications
• #bacterial biofilms and quorum sensing
• #benzothiazole

Antibacterial, antibiofilm and anti-quorum sensing activities of 1,2,3,5-tetrazine derivatives linked to a benzothiazole moiety

Jean Paul Dzoyem, Joseph Tsemeugne, Boniface Pone Kamdem, Rostand Foyou Meupiap, Boris Arnaud Kuate, Pierre Mkounga et 2 autre(s)

PLoS ONE

A series of known tetrazine derivatives, containing benzothiazole scaffold, were prepared during the coupling reactions of selected diazotized 2-aminobenzo[d]thiazole derivatives with p-acetaminophen. The as-prepared compounds were characterized based on NMR and MS spectrometry. The antibacterial and anti-biofilm activities of the synthesized compounds were evaluated by microdilution method, whereas the anti-quorum sensing effect was carried out using assay for the inhibition of violacein formation. As a result, compounds 4a, 4b and 4c revealed minimum inhibitory concentrations and minimum bactericidal concentrations ranging from 8 to 128 µg/mL and from 32 to 256 µg/mL, respectively. Compounds 4a (52-86.5%), 4b (57.7-79.4%) and 4c (59.9-80.3%) prevented biofilm formation in all the four bacteria tested with percentages of inhibition more than 50%. The concentrations of 4a, 4b and 4c that inhibited 50% of violacein production were found to be 62.71, 28.56 and 107.45 µg/mL, respectively, thus attesting that these compounds possess anti-quorum sensing activity. Noteworthy, our previous investigation attested that these compounds are non-cytotoxic on the human mammalian cells Vero. This novel contribution demonstrates the antibacterial, antibiofilm and anti-quorum sensing activities of tetrazine-based benzothiazoles, which might be prospected as scaffolds for the discovery of efficient antibiotics with decreased risk of microbial drug resistance.

• #phenothiazines and benzothiazines synthesis and activities
• #bacterial biofilms and quorum sensing
• #antimicrobial agents and applications
• #benzothiazole

Bio‐guided investigation of nine Niger’s ethnomedicinal plants reveals nature‐derived antimalarial chemical pharmacophores for drug discovery

Mahamane Idi Issa Abdoulahi, Mariscal Brice Tchatat Tali, Ilagouma Amadou Tidjani, Hama Hamadou Habibou, Paul Etoga Mbarga, Darline Dize et 6 autre(s)

Chemistry & Biodiversity

ABSTRACT Malaria is a significant concern due to the emergence of artemisinin‐resistant parasites. This study aims to unveil the selective inhibitory potential of extracts and derivatives of some Niger's plants against Plasmodium falciparum . Plant extracts were screened on chloroquine‐sensitive ( Pf 3D7) and multidrug‐resistant ( Pf Dd2) P. falciparum strains using the SYBR Green method, followed by bio‐guided fractionation of active extracts. Bio‐guided method was used for the isolation. Resazurin‐based and hemoglobin quantification assays were used to assess the selectivity on normal RAW cells and erythrocytes, respectively. Among the 27 extracts, five exhibited pronounced activity (IC 50 < 5 µg/mL) against multidrug‐resistant ( Pf Dd2) and three against sensitive ( Pf 3D7) strains of P. falciparum . The methanolic extract from Phyllanthus pentandrus displayed the most promising activity the most active on both strains (IC 50 Pf Dd2 = 1.85 µg/mL and IC 50 Pf 3D7 = 4.25 µg/mL). Its fractionation led to five fractions, among which the ethyl acetate fraction was the most active (IC 50 Pf Dd2 = 3.10 µg/mL). Four compounds were isolated from the ethyl acetate fraction: kaempferol, quercetin, gallic acid, and quercetin‐3‐O‐rutinoside. Active extracts and fractions showed good selectivity on normal RAW cells and erythrocytes. This study validates the medicinal use of Niger ethnomedicine for the treatment of malaria.

• #phytochemistry and bioactivity studies
• #malaria research and control
• #research on leishmaniasis studies
• #chemistry

Diversité floristique et ph du sol des habitats de <i>Asparagus drepanophyllus</i> Welw. Ex baker à Nkolondom, Cameroun

Emilienne Pola Yissibi, Vice Clotèxe Tajeukem, Hubert Mounmemi Kpoumie, Nicole Maffo Maffo, Pierre Mkounga, Claudine Ntsama Essomba et 1 autre(s)

International Journal of Biological and Chemical Sciences

Asparagus drepanophyllus Welw. ex Baker (Asparagaceae) est très exploitée pour ses vertus médicinales. Dans le cadre de la valorisation des ressources végétales d'intérêt médicinale au Cameroun, une étude a été réalisée dans la localité de Nkolondom, département du Mfoudi, Région du Centre. L’objectif était de caractériser son habitat naturel, afin de contribuer à une meilleure connaissance de son écologie. A cet effet, une détermination du pH par lecture directe au pH-mètre d’échantillons de sol prélevés à 30 cm de profondeur, puis un inventaire floristique consistant à dresser la liste quantitative et qualitative des espèces végétales ont été faits. Les résultats de cette étude ont montré que : dans la zone étude, le sol était acide avec un pH moyen de 4,85; A. drepanophyllus avait une Abondance absolue de 352 pieds/ha (Abondance relative : 11%). 93 espèces réparties dans 86 genres et 48 familles ont été recensées ; la strate des herbacées représentait 86% de la végétation avec un indice de diversité de Shannon de 3,65 bits, contre 14% pour la strate d’arbres et arbustes, avec un indice de diversité de Shannon de 0,97 bit. Ce travail constitue une base pour la domestication d’A. drepanophyllus, en vue du développement standardisé de phytomédicaments. Asparagus drepanophyllus Welw. ex Baker, is widely used for its medicinal properties. As part of efforts to promote the use of medicinal plants in Cameroon, a study was conducted in the locality of Nkolondom, Mfoudi Department, Central Region. The objective was to characterize its natural habitat in order to contribute to a better understanding of its ecology. To this end, pH was determined by direct reading with a pH meter of soil samples taken at a depth of 30 cm, followed by a floristic inventory consisting of compiling a quantitative and qualitative list of plant species. The results of this study showed that: in the study area, the soil was acidic with an average pH of 4.85; A. drepanophyllus had an absolute abundance of 352 plants/ha (relative abundance: 11%). 93 species distributed among 86 genera and 48 families were recorded; the herbaceous layer represented 86% of the vegetation with a Shannon diversity index of 3.65 bits, compared to 14% for the tree and shrub layer, with a Shannon diversity index of 0.97 bits. This work provides a basis for the domestication of A. drepanophyllus, with a view to the development of standardized phytomedicines.

• #phytochemical studies and bioactivities
• #african botany and ecology studies
• #ethnobotanical and medicinal plants studies
• #environmental factor

Functional analysis of quinovic acid derivatives from Sarcocephalus pobeguinii as inhibitors of hepatitis C virus NS3/4A protease

Arnaud Fondjo Kouam, Aristide Mfifen Munvera, Jordas Casares Tchana Tchamba, Elisabeth Menkem Zeuko’o, Armelle Gaelle Kwesseu Fepa, Brice Fredy Nemg Simo et 6 autre(s)

Pharmacological Research - Reports

• #hepatitis c virus research
• #liver disease diagnosis and treatment
• #animal virus infections studies
• #ns3

Phytochemical and Antibacterial Studies of the Ethanolic Stem Barks Extract of Anthocleista Vogelii Planch, and the in Silico Study of its Secondary Metabolites on Two Bacteria Strains Staphylococcus Aureus and Salmonella Typhi

Tengu Awazi, Judith Caroline Ngo Nyobe, Baruch ATEBA AMANA, Clemencia Iwo, Maraf Mbah Bake, Tsahnang Fofack Hans Merlin et 4 autre(s)

SSRN Electronic Journal

• #bioactive compounds and antitumor agents
• #natural product bioactivities and synthesis
• #essential oils and antimicrobial activity
• #phytochemical

Synthesis, antioxidant activity of novel sulfonamide and sulfonate organic salts bearing various heterocyclic moieties

Didier Forest Kouganou Djossu, Joseph Tsemeugne, Paul Etoga Mbarga, Jean‐De‐Dieu Tamokou, Germaine Takongmo Matsuete, Armelle Tontsa Tsamo et 6 autre(s)

Future Medicinal Chemistry

AIM: The reactions of various heterocyclic primary amines with sulfonyl chloride derivatives or with sulfosalicylic acid results in the first case to the formation of sulfonamide derivatives and in the second case to the formation of sulfonate organic salts which are both hybrid molecule that integrate multiple pharmacophores into a single scaffold. MATERIALS AND METHODS: The novel sulfonamide derivatives 3 were obtained through mono-nucleophilic addition reactions of the corresponding primary amines to the appropriate sulfonyl derivative. In contrast, the sulfonate organic salts 5, 7 and 8 were formed as the result of an acid-base neutralization reaction, during which a molecule of amine captures the acid proton from the sulfosalicylic acid molecule. The antioxidant activity of the synthesized compounds is evaluated by determining their DPPH (2,2-Diphenyl-1-picrylhydrazyl) free radical scavenging activity as well as gallic acid equivalent antioxidant capacity (GEAC). RESULTS AND CONCLUSION: C-NMR (Carbon-13 nuclear magnetic resonance) and HRMS (High-Resolution Mass Spectrometry) spectroscopic data. Organic salt 7a was characterized by single-crystal and X-ray diffraction. Organic sulfonate salts were found to be more active than covalent sulfonamide derivatives.

• #enzyme function and inhibition
• #sulfur-based synthesis techniques
• #organic and inorganic chemical reactions
• #chemistry

Assessment of the Authenticity and Detection of Fraud in Artisanal Red Palm Oil Sold in Markets in Douala and Yaoundé, Cameroon

Horchelle T. Djomptchouang, Wilfred A. Abia, Angèle N. Tchana, Gilbert Manga Mbassi, Pierre Mkounga, Élie Fokou

Clinical Research and Reports

Introduction: Red palm oil is the most consumed vegetable oil in the World. RPO obtained from the mesocarp of the palm nuts is characterised by a deep red colour greatly appreciated by consumers. Its popularity has made it vulnerable to fraud, perpetrated partly to meet demands but mainly for economic gains. Recently, red palm oil adulteration has been reported in West Africa; the main suspected adulterant, Sudan dyes, had beenbanned as food additives by the WHO due to their perceived carcinogenicity. However, there is inadequate data from Cameroon concerning red palm oil adulteration. This study has assessed the authenticity of red palm oil and detected the presence of various adulterants in red palm oil samples collected from some local markets in Douala and Yaounde, Cameroon. In addition, it has proposed a simple rapid technique for detecting the presence of Sudan dye in red palm oil. Methodology: Red palm oil samples (N=86) were collected from some major markets in Douala (n=49) and Yaounde (n=37) and analyzed for some authenticity-related parameters (moisture content, acid value, free fatty acids), as well as fraud detection: the case of Sudan dye. Results and Discussion: Moisture content analysis of the red palm oil samples revealed a mean (range) of 2.21 (0.25-29.14) % with 85 (99%) samples being above the Codex Alimentarius standard value of 0.25%. For acid value, a mean value of 32.47 (range: 14.03-84.15) mg NaOH/g of red palm oil was detected. For free fatty acids, a mean level of 14.8 3 (range: 6.40-38.42) % was detected. Altogether, three samples (~ 4%) tested positive for Sudan dye and were considered suspicious. Additionally, the studied red palm oil samples were not authentic and were suspected to be adulterated with water (99%) and Sudan dye (~4%). Conclusion: For the first time, this paper reports on red palm oil authenticity and fraud detection in Cameroon. Water and Sudan dye were the suspected adulterants, requiring further studies and public attention.

• #oil palm production and sustainability
• #palm oil
• #palm
• #traditional medicine

Cultivability of <i>Escherichia Coli</i> and <i>Staphylococcus Aureus</i> in the Presence of Hydroethanolic Extracts of <i>Lantana Camara</i> Stems and Leaves: Importance of Bioactive Compounds in the Cellular Inhibition Process

Carlain Emar Tchapo Djappa, Fils Mamert Onana, Antoine Tamsa Arfao, Claire Stéphane Metsopkeng, Maka Mouande Arnold Alex, Sophie Laurent et 4 autre(s)

SSRN Electronic Journal

• #phytochemistry medicinal plant applications
• #staphylococcus aureus
• #escherichia coli
• #lantana camara

Cultivability of Escherichia coli and Staphylococcus aureus in the presence of hydroethanolic extracts of Lantana camara stems and leaves: Importance of bioactive compounds in the cellular inhibition process

Carlain Emar Tchapo Djappa, Fils Mamert Onana, Antoine Tamsa Arfao, Claire Stéphane Metsopkeng, Maka Mouande Arnold Alex, Sophie Laurent et 4 autre(s)

Scientific African

The presence of pathogenic micro-organisms in drinking water is responsible for certain public health diseases. The use of plant extracts is an alternative to commonly used chemical and physical treatments. The aim of this study is to evaluate the hydroethanolic extracts of Lantana camara stems and leaves on the cultivability of planktonic bacteria Escherichia coli and Staphylococcus aureus in an aquatic microcosm, to determine the effect of extract concentration (0,5 g/L, 1 g/L, 1,5 g/L and 2 g /L), incubation temperature (7 and 37 °C) and incubation time (3, 6 and 9 hours) on the cultivability of bacterial cells and also to evaluate the effect of some bioactive compounds isolated from these bacteria. The bioactive compounds identified are Stigmasterol (sterol), lantanilic acid and lantic acid (triterpenes) isolated in the leaf extract of L. camara and β-sistosterol (sterol) and oleanolic acid (triterpenes) isolated in the stem extract of L. camara . The cultivability of two bacterial strains studied is influenced by the presence of Lantana camara extract solution. A reduction in cell density was observed in the presence of the plant extract in question. With Lantana camara leaf extract, at an incubation temperature of 37 °C, the percentage of inhibition ranged from 3–100% for E. coli with the highest value observed after 6 hours at extract concentrations of 1.5 g/L and 2 g/L. In general, the extract has both a bactericidal and bacteriostatic effect on each bacterium, depending on the type of organ, whereas the effect of the bleach is specific to each bacterium. It should be noted that in the presence of E. coli , the MICs were 0.00048 mg/mL with the leaf extract and 0.0078 mg/mL with the stem extract. For this bacterium, the MBCs were 0.0039 mg/mL and 0.0312 mg/mL with the leaf and stem extracts respectively. For S. aureus , the MICs were 0.0156 mg/mL with the leaf extract and 0.0078 mg/mL with the stem extract and the MBCs were 0.0019 mg/mL and 0.0156 mg/mL (leaf and stem, respectively). The CMB/MIC ratio shows a bactericidal effect at the level of β-sistosterol in E. coli . On the other hand, in S. aureus , this report shows a bacteriostatic effect and tolerance with the two isolated chemical compounds. The Kruskal-Wallis test shows that the abundance of cultivable cells of each bacterial species differed significantly from one incubation temperature to another at each extract concentration and at each incubation temperature for each part of the plant (P<0.05). The data obtained from this exploratory study makes it possible to consider the use of Lantana camara hydroethanolic extract as an alternative method in water disinfection .

• #essential oils and antimicrobial activity
• #phytochemistry medicinal plant applications
• #ethnobotanical and medicinal plants studies
• #lantana camara

Repurposing of Synthetic Acetaminophen Derivatives Containing Benzothiazole Scaffold as Alternative Therapy for Infectious Diarrhea Caused by Drug-Resistant Shigella Species

Boniface Pone Kamdem, Brice Rostan Pinlap, Bijou-Lafortune Noumboue Kouamou, Aubin Youbi Kamche, Boris Arnaud Kuate, Joseph Tsemeugne et 3 autre(s)

Preprints.org

Diarrhea remains one of the leading causes of mortality worldwide, especially among children. Recent epidemiological studies conducted in developing countries identified Shigella species as the most predominant pathogenic bacteria responsible for diarrhea. Antimicrobial therapy is necessary for Shigella infections; however, the rapid emergence of resistance against existing antimicrobials in Shigella spp. poses a serious global health problem. To identify alternative antimicrobial compounds with activity against Shigella species, the pathogens responsible for bacterial diarrhea. In this study, we have applied antibacterial phenotypic screening to identify potent anti-Shigella compounds across a broad chemical diversity, including selected acetaminophen derivatives containing benzothiazoles backbone, and their combination with certain antibiotics. In continuation to our effort in searching potent antimicrobial compounds, we have found this time around that two acetaminophen derivatives containing benzothiazoles backbone (4a and 4b) could inhibit the growth of Shigella flexneri with common MIC value of 12.5 µg/ml. These compounds were established through a time-kill kinetics’ study to be bactericidal. Meanwhile, the 2-aminobenzothiazoles (1a and 1b) used for the synthesis of compounds 4 (a &amp;amp; b) were found to be poorly active (MIC: 100 µg/ml) against this pathogen. Combination studies of 4a and 4b with the least susceptible antibiotics (ceftriaxone and cotrimoxazole) demonstrated synergistic anti-Shigella activity. The present study demonstrates that the azobenzothiazole dyes 4 (a &amp;amp; b) can be repurposed as potential anti-Shigella compounds, which can serve as scaffolds for the development of new agents against infectious diarrhea caused by Shigella and other enteric pathogens, especially in developing countries.

• #viral gastroenteritis research and epidemiology
• #veterinary medicine and infectious diseases
• #clostridium difficile and clostridium perfringens research
• #benzothiazole

Repurposing Synthetic Acetaminophen Derivatives Containing a Benzothiazole Scaffold as an Alternative Therapy for Infectious Diarrhea Caused by Drug-Resistant Shigella Species

Boniface Pone Kamdem, Brice Rostan Pinlap, Bijou-Lafortune Noumboue Kouamou, Aubin Youbi Kamche, Boris Arnaud Kuate, Joseph Tsemeugne et 3 autre(s)

Future Pharmacology

Diarrhea remains one of the leading causes of mortality worldwide, especially among children. Accumulated evidence has shown that Shigella species are the most prevalent bacteria responsible for diarrhea in developing countries. Antimicrobial therapy is necessary for Shigella infections; however, the development of resistance against current drugs justifies the pressing need to search for alternative medications. In this study, we have applied antibacterial phenotypic screening to identify potent anti-Shigella compounds across a broad chemical diversity, including selected acetaminophen derivatives containing a benzothiazole backbone, and their combination with certain antibiotics. As a result, two acetaminophen derivatives containing a benzothiazole backbone (4a and 4b) inhibited the growth of Shigella flexneri with a common MIC value of 12.5 µg/mL. These compounds were established through a time-kill kinetics study to be potentially bactericidal. Meanwhile, the 2-aminobenzothiazoles (1a and 1b) used for the synthesis of compounds 4 (a and b) were found to be poorly active (MIC: 100 µg/mL) against this pathogen. Combination studies of 4a and 4b with the least effective antibiotics (ceftriaxone and cotrimoxazole) demonstrated synergistic anti-Shigella activity with MIC values decreasing from 12.5 to 0.781 μg/ mL. The present study demonstrates that the azobenzothiazole dyes 4 (a and b) can be repurposed as potential anti-Shigella compounds, thus providing potential chemical pharmacophores for the discovery of drugs against infectious diarrhea caused by Shigella and other enteric pathogens, especially in developing countries.

• #viral gastroenteritis research and epidemiology
• #veterinary medicine and infectious diseases
• #tuberculosis research and epidemiology
• #benzothiazole

Synthesis, Antibacterial and Antibiofilm Activity of New 1,2,3,5-Tetrazine Derivatives from Coupling Reactions of Diazonium Salt of 2-Amino-6-nitrobenzothiazole With Diverse Substituted 2-Aminobenzothiazole Derivatives

Joseph Tsemeugne, Yetiny Atuh Bah, Ulrich Joël Tsopmene, Armelle Tontsa Tsamo, Jérôme Ndefo Ndefonganga, Pierre Mkounga et 3 autre(s)

Acta chimica slovenica

The coupling reaction of diazonium ion of 2-amino-6-nitrobenzothiazole at 0-5 °C with distinctly substituted 2-aminobenzothiazole derivatives produced new 1,2,3,5-tetrazine derivatives. It was found that diazotized 2-amino-6-nitrobenzo[d]thiazol reacts with the ring nitrogen atom of varyingly substituted 2-aminobenzothiazole derivatives to yield tetrazine nucleus. The benzene ring of benzothiazole bearing electron donor group and annelated to the tetrazine was further substituted in situ by other 6-nitrobenzo[d]thiazol-2-yl) diazinyl to yield the final product. The structure of the prepared compounds was elucidated using their physical, elemental, and spectroscopic data. The synthesized compounds were tested for their antimicrobial and antibiofilm activities against Staphylococcus aureus and Escherichia coli bacteria. Two of the synthesis tetrazine derivatives exhibited interesting antibiofilm potential.

• #synthesis and characterization of heterocyclic compounds
• #click chemistry and applications
• #synthesis and biological activity
• #tetrazine

Three New Polyphenol Derivatives from the Fruits of Macaranga Monandra and their Antioxidant Potential

Einstein Guizoko Toko, Carlain Emar Djappa Tchapo, Armelle Tontsa Tsamo, Raoul Kemzeu, Yan Wang, Fabrice Fekam Boyom et 5 autre(s)

Chemistry & Biodiversity

Phytochemical investigation of the methanol extract from the fruits of Macaranga monandra (Euphorbiaceae Muell. et Arg.) afforded one new geranylated 1',2'-dihydrophenanthrene and two new flavonoid derivatives, named macamondrin (1), macamondrione A (2) and B (3) respectively. The structures of these compounds were elucidated mainly by NMR, mass spectral data and in comparison with data from the literature. Along with compounds 1-3, nine known compounds among which oleanolic acid (4); daucosterol (5); 3β-acetoxy-11α,12α-epoxytaraxerol (6); 3,3',4-tri-O-methylellagic acid (7); 3,3',4,4'-tetra-O-methylellagic acid (8); 4'-O-methyl-6-isoprenylapigenin (9); 4'-O-methyl-8 isoprenylkaempférol (10); 4'-O-methyl-6-isoprénylkaempférol (11); 6-isoprénylkaempférol (12), were also isolated. Crude extracts as well as isolated compounds were evaluated for their antioxidant activity using the ABTS, DPPH and FRAP methods. It appears that the 50 % radical scavenging concentrations ranging from 6.26 to 11.7 μg/ml on the ABTS radical, from 1.77 to 48.22 μg/ml on the DPPH radical, and from 1.54 to 67.97 μg/ml with the FRAP method. For the compounds tested, very good antioxidant activities were observed, which clearly shows that these molecules can have an anti oxidative stress potentiel.

• #bioactive natural compounds
• #phytochemicals and antioxidant activities
• #natural product bioactivities and synthesis
• #chemistry

Cholinesterase, α-glucosidase, tyrosinase and urease inhibitory activities of compounds from fruits of Rinorea oblongifolia C.H. Wright (Violaceae)

Aristide Mfifen Munvera, Alfred Ngenge Tamfu, Blandine Marlyse Wache Ouahouo, Selçuk Küçükaydın, Jean Noël Nyemb, Marcelle Aude Fokam Mafo et 3 autre(s)

Natural Product Research

From Rinorea oblongifolia fruits, 3-Nor-4β-friedelan-24-ol (1) and 3-decyl-6,7,8-trimethoxy-2H,5H-furo[4,3,2-de]isochromene-2,5-dione (4), new derivatives alongside, 28-hydroxyfriedelan-3-one (2), friedelin (3), 3,3’,4,4’,5’-pentamethylcoruleoellagic acid (5), hexamethylcoruleoellagic acid (6), 3’,4,4’,5,5’-pentamethylcoruleoellagic acid (7), and fatty compounds 8-11 were isolated and characterized using HRESIMS, EIMS, 1D and 2D NMR. In vitro enzyme inhibition of compounds 1, 2, 4, 5, 6 and 7 were evaluated on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-glucosidase, urease and tyrosinase. Against AChE and BChE, the phenolic compounds 4, 5, 6, and 7 had good activity probably due to the phenolic nature and methoxy substituents. Compounds 4, 5, 6 and 7 exhibited good α-glucosidase inhibition especially compound 4 whose IC50 = 42.45 ± 0.46 µg/mL was close that of acarbose (IC50 = 20.52 ± 0.84 µg/mL) standard drug. Urease and tyrosinase were appreciably inhibited by the compounds. Overall results of enzyme inhibitory assays indicate Rinorea oblongifolia, fruits and its constituents as potential remedy for enzymatic disorders.

• #phytochemistry and bioactivity studies
• #chemical synthesis and alkaloids
• #phytochemistry and biological activities
• #tyrosinase

Connaissance, identification et étude phytochimique de deux plantes médicinales appelées «ginseng» à Yaoundé (Cameroun)

Emilienne Pola Yissibi, Vice Clotèxe Tajeukem, Hubert Mounmemi Kpoumie, Aristide Mfifen Munvera, Nicole Maffo Maffo, Aristide Mfifen Munvera et 5 autre(s)

International Journal of Biological and Chemical Sciences

La forte demande des préparations à base de racines de Panax ginseng C.A. Meyer (Araliaceae), pour ses propriétés adaptogènes, a motivé la commercialisation de plantes de taxonomies différentes sous la désignation « ginseng ». Sachant que P. ginseng, « véritable ginseng », doit ces propriétés surtout aux saponosides et polysaccharides, et qu’il est cultivé principalement dans les régions tempérées froides, ce travail visait à contribuer à la connaissance des plantes médicinales dont les racines sont appelées « ginseng » à Yaoundé. Un criblage phytochimique des macérats aqueux et hydroalcooliques des racines fraiches broyées a complété une enquête ethnobotaniques menée auprès de 400 personnes. On a ainsi évalué l’état de leurs connaissances de la ressource et identifié deux espèces botaniques de familles différentes : Asparagus drepanophyllus Welw. ex Baker (Asparagaceae) et Vernonia guineensis Benth. (Asteraceae). 51% des personnes déclarant connaitre le « ginseng » avaient des sources d’information informelles peu fiables (médias, publicités, véhicules de transports en commun) et n’avaient jamais vu la plante entière. Les racines étaient les parties les plus sollicitées (67%) tandis que la décoction (37%), l’infusion (33%) et la macération (17%) étaient les modes de préparation les plus fréquents. Les saponines et les polysaccharides étaient très présents dans les extraits aqueux des racines des 2 espèces alors que les composés phénoliques, anthocyaniques, flavonoïdes et les tanins présents chez V. guineensis étaient absents chez A. drepanophyllus. Ces principaux groupes chimiques pourraient justifier leur utilisation comme adaptogènes mais la connaissance de la ressource est insuffisante et ce travail peut constituer un apport scientifique à la sécurité des produits de santé à base de plantes vendus librement. English title: Knowledge, identification and phytochemical study of two medicinal plants called «ginseng» in Yaoundé (Cameroon) The high demand for ginseng root preparations, Panax ginseng C.A. Meyer (Araliaceae) for its adaptogenic properties has led to the marketing of plants of different taxonomies under the designation «ginseng». Knowing that P. ginseng, "real ginseng", owes these properties especially to saponosides and polysaccharides, and that it is grown mainly in cold temperate regions, this work aimed to contribute to the knowledge of medicinal plants whose roots are called “ginseng” in Yaoundé. A phytochemical screening of aqueous and hydroalcoholic macerates of fresh ground roots completed an ethnobotanical survey conducted among 400 people. We assessed their knowledge of the resource and identified two botanical species from two different families: Asparagus drepanophyllus Welw. ex Baker (Asparagaceae) and Vernonia guineensis Benth. (Asteraceae). 51% of people who said they know “ginseng” have unreliable informal sources of information (media, advertising, public transport vehicles) and have never seen the whole plant. Roots were the most frequently used parts (67%). Decoction (37%), infusion (33%) and maceration (17%) were the most common methods of preparation. Saponins and polysaccharides were very present in the aqueous extracts of the roots of both species while phenolic compounds, anthocyanins, flavonoids and tannins present in V. guineensis were absent in A. drepanophyllus. These major chemical groups may justify their use as adaptogens but there is insufficient knowledge of the resource and this work can be a scientific contribution to the safety of freely sold herbal health products.

• #african botany and ecology studies
• #natural product bioactivities and synthesis
• #ginseng biological effects and applications
• #ginseng

Effect of the synthons O—H (sec. alcohol)...O=C (ketone) and C sp 2 –H (furan)...OOC (acetate) in the supramolecular packings of two bioactive molecules

T. P. Kenfack, T. A. Tontsa, Pamela Kemda Nangmo, T. S. Kenfack, Pierre Mkounga, Ephrem Augustin Nkengfack et 1 autre(s)

Acta Crystallographica Section A Foundations and Advances

• #chemical synthesis and analysis
• #synthesis and reactivity of sulfur-containing compounds
• #molecular spectroscopy and chirality
• #synthon

In vitro antiproliferative, anti-inflammatory effects and molecular docking studies of natural compounds isolated from Sarcocephalus pobeguinii (Hua ex Pobég)

Emmanuel Mfotie Njoya, Brigitte Ndemangou, Jude Akinyelu, Aristide Mfifen Munvera, Chika I. Chukwuma, Pierre Mkounga et 3 autre(s)

Frontiers in Pharmacology

Background: Sarcocephalus pobeguinii (Hua ex Pobég) is used in folk medicine to treat oxidative-stress related diseases, thereby warranting the investigation of its anticancer and anti-inflammatory properties. In our previous study, the leaf extract of S. pobeguinii induced significant cytotoxic effect against several cancerous cells with high selectivity indexes towards non-cancerous cells. Aim: The current study aims to isolate natural compounds from S. pobeguinii , and to evaluate their cytotoxicity, selectivity and anti-inflammatory effects as well as searching for potential target proteins of bioactive compounds. Methods: Natural compounds were isolated from leaf, fruit and bark extracts of S. pobeguinii and their chemical structures were elucidated using appropriate spectroscopic methods. The antiproliferative effect of isolated compounds was determined on four human cancerous cells (MCF-7, HepG2, Caco-2 and A549 cells) and non-cancerous Vero cells. Additionally, the anti-inflammatory activity of these compounds was determined by evaluating the nitric oxide (NO) production inhibitory potential and the 15-lipoxygenase (15-LOX) inhibitory activity. Furthermore, molecular docking studies were carried out on six putative target proteins found in common signaling pathways of inflammation and cancer. Results: Hederagenin ( 2 ), quinovic acid 3-O-[α-D-quinovopyranoside] ( 6 ) and quinovic acid 3-O-[β-D-quinovopyranoside] ( 9 ) exhibited significant cytotoxic effect against all cancerous cells, and they induced apoptosis in MCF-7 cells by increasing caspase-3/-7 activity. ( 6 ) showed the highest efficacy against all cancerous cells with poor selectivity (except for A549 cells) towards non-cancerous Vero cells; while ( 2 ) showed the highest selectivity warranting its potential safety as a chemotherapeutic agent. Moreover, ( 6 ) and ( 9 ) significantly inhibited NO production in LPS-stimulated RAW 264.7 cells which could mainly be attributed to their high cytotoxic effect. Besides, the mixture nauclealatifoline G and naucleofficine D ( 1 ), hederagenin ( 2 ) and chletric acid ( 3 ) were active against 15-LOX as compared to quercetin. Docking results showed that JAK2 and COX-2, with the highest binding scores, are the potential molecular targets involved in the antiproliferative and anti-inflammatory effects of bioactive compounds. Conclusion: Overall, hederagenin ( 2 ), which selectively killed cancer cells with additional anti-inflammatory effect, is the most prominent lead compound which may be further investigated as a drug candidate to tackle cancer progression.

• #natural product bioactivities and synthesis
• #genomics, phytochemicals, and oxidative stress
• #synthesis and biological activity
• #chemistry

Natural Compounds Isolated from African Mistletoes (Loranthaceae) Exert Anti-Inflammatory and Acetylcholinesterase Inhibitory Potentials: In Vitro and In Silico Studies

Emmanuel Mfotie Njoya, Hermine L.D. Maza, Shasank S. Swain, Chika I. Chukwuma, Pierre Mkounga, Yves Martial Mba Nguekeu et 3 autre(s)

Applied Sciences

Despite the medicinal uses of Phragmanthera capitata, Globimetula dinklagei and Tapinanthus bangwensis against memory loss, convulsions and pain, their efficacy against brain-dysfunction diseases and inflammation models has not yet been studied. Therefore, this study aims to investigate the anti-inflammatory and acetylcholinesterase (AChE) inhibitory potentials of their crude extracts and isolated natural compounds by combining in vitro and in silico experiments. Crude extracts and isolated compounds were tested in vitro for their AChE inhibitory activity by using Ellman’s method. Additionally, their anti-inflammatory activity was determined by evaluating the nitric oxide (NO) production inhibitory activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells and the 15-lipoxygenase (15-LOX) inhibitory activity by using the ferrous oxidation xylenol orange assay. Furthermore, the in silico efficacy of natural compounds was investigated against ten putative target enzymes relevant in Alzheimer’s disease (AD) pathogenesis and inflammation. It was found that the crude extracts had weak to moderate inhibitory potential against AChE, with the extract of T. bangwensis being the most active (50% inhibitory concentration (IC50) = 48.97 µg/mL). Six natural compounds, namely, 3-O-β-D-glucopyranosyl-28-hydroxy-α-amyrin (2), apigenin- 8-C-β-D-glucopyranoside (3), globimetulin B (5), globimetulin C (6), bangwaursene B (8) and 3β-acetoxy-11,12-epoxytaraxerol (9), were identified for the first time as having anti-AChE potential, among which (9) had the highest efficacy with an IC50 of 13.89 µM. Among the anti-AChE compounds, (5) was also efficient against NO production and 15-LOX, and the data are in agreement with the docking score. In summary, compounds (5) and (9) are the most prominent lead compounds that should be further tested experimentally against molecular targets of AD and inflammation.

• #cholinesterase and neurodegenerative diseases
• #allelopathy and phytotoxic interactions
• #toxin mechanisms and immunotoxins
• #acetylcholinesterase

Phytochemical Screening and Antibacterial Potential of the Trunk Bark of Ochthocosmus Africanus

Viviane Raïssa Sipowo Tala, Olivier Tene Tcheghebe, Marcime Zavier Yamdjeu Happi, Ernest Tambo, Aristide Mfifen Munvera, Pierre Mkounga et 2 autre(s)

International Journal of Pharmaceutical and Phytopharmacological Research

An estimated 57 million deaths are recorded worldwide every year out of which infectious diseases are responsible for 17 million; one-third of the overall mortality rate. To face this crucial issue, the search for new anti-infective agents that could be used by needy populations appeared primordial. The present study focused on Ochthocosmus africanus (Ixonanthaceae) known to be traditionally used in disease caretaking. The phytochemical screening of the hydroalcoholic extract from the plant trun

• #essential oils and antimicrobial activity
• #moringa oleifera research and applications
• #african botany and ecology studies
• #phytochemical

Variability in indigenous knowledge and practices of wood treatments against termites in the cities of Yaoundé and Douala (Cameroon) and their status

F. J. O. Feumba, Evariste Fongnzossie Fedoung, C. L. T. Djuideu, Achille Bernard Biwôlé, Joseph Mfomo Zobo, F M Ngangyou et 3 autre(s)

European Journal of Sustainable Development Research

The aim of this study was to describe the wood treatment sector in the cities of Douala and Yaoundé (Cameroon). A total of 319 semi-structured interviews were conducted. The respondents were agents of wood depots, sawmills, hardware stores, and carpentry shops. They were asked about the diversity of products used and their perception of the risks and dangers of treatments. The chemical method (40.4%) was the main means of preserving wood against termite attack according to the respondents, followed by the traditional method with 9.4%, the physical method (2.2%) and more rarely, the use of plant extract (0.3%). All the chemicals were found to be hazardous to the environment and human health, with Xylamon being classified as the most hazardous. The physical control methods and those using plant extracts were found to be not at all dangerous for human health and the environment. Notwithstanding concerns for the protection of the environment and human health, toxic and hazardous products are still predominantly used. It would be important to move towards less or non-toxic products.

• #insect and arachnid ecology and behavior
• #african botany and ecology studies
• #insect utilization and effects
• #hazardous waste

CCDC 2063672: Experimental Crystal Structure Determination

Julio Issah Mawouma Pagna, Ines Michèle Kanko Mbekou, Armelle Tontsa Tsamo, Pierre Mkounga, Marcel Frese, Hans‐Georg Stammler et 4 autre(s)

The Cambridge Structural Database

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

• #crystallization and solubility studies
• #x-ray diffraction in crystallography
• #crystallography
• #crystal structure

CCDC 2159930: Experimental Crystal Structure Determination

Paul Etoga Mbarga, Hugues Fouotsa, Brigite Ndemangou, Julio Issah Mawouma Pagna, Ines Michèle Kanko Mbekou, Pierre Mkounga et 6 autre(s)

The Cambridge Structural Database

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

• #crystallization and solubility studies
• #x-ray diffraction in crystallography
• #crystallography
• #materials science

Chemical constituents from Dicraenthus zehnderi H. hess and their chemotaxonomic significance

Maurice Tsaffack, Aristide Mfifen Munvera, Marlyse W. Ouahouo, Alfred Ngenge Tamfu, Pierre Mkounga, Augustin E. Nkengfack

Biochemical Systematics and Ecology

• #bioactive natural compounds
• #chemical synthesis and alkaloids
• #marine sponges and natural products
• #phytochemical

Chemical Constituents from Dicraenthus Zehnderi H. Hess and Their Chemotaxonomic Significance

Maurice Tsaffack, Aristide Mfifen Munvera, Marlyse Ouahouo, Alfred N. TAMFU NGENGUE, Pierre Mkounga, Augustin Ephrem Nkengfack

SSRN Electronic Journal

• #medicinal plant effects and applications
• #bryophyte studies and records
• #phytochemistry and biological activities
• #biology

Khaya grandifoliola active fraction as a source of therapeutic compounds for Alzheimer’s disease treatment: In silico validation of identified compounds

Brice Ayissi Owona, Frédéric Nico Njayou, Pierre Mkounga, Paul Fewou Moundipa

In Silico Pharmacology

• #natural product bioactivities and synthesis
• #bioactive compounds and antitumor agents
• #seaweed-derived bioactive compounds
• #chemistry

Secondary metabolites from Detarium microcarpum Guill. and Perr. (Fabaceae)

William F. Feudjou, Arnaud M. Mbock, Valérie Tedjon Sielinou, Hugue Fouotsa, Steven Collins Njonté Wouamba, Racéline Kamkumo Gounoue et 8 autre(s)

Zeitschrift für Naturforschung C

Abstract The chemical investigation of the ethanol/water (7:3) extract of the roots of Detarium microcarpum (Fabaceae) led to the isolation of one new labdane diterpenoid, microcarpin ( 1 ) and one new ceramide derivative, microcarpamide ( 2 ), along with eight known secondary metabolites ( 3–10 ) including, 5-(carboxymethyl)-5,6,8a-trimethyl-3,4,4a,5,6,7,8,8a-octahydronaphthalene-1-carboxylic acid ( 3 ), microcarposide ( 4 ), rhinocerotinoic acid ( 5 ), 1,7-dihydroxy-6-methylxanthone ( 6 ), ursolic acid ( 7 ), 3 β ,23-dihydroxylup-20(29)-en-28-oic acid ( 8 ), alphitolic acid ( 9 ), and stigmasterol glucoside ( 10 ). The structures of these compounds were elucidated based on their spectroscopic data. Although compounds 3 and 4 are known, their crystalline structures are reported here for the first time. These compounds were evaluated in vitro for their antisalmonella activity. The results obtained showed that, microcarpamide ( 2 ), microcarposide ( 4 ), and rhinocerotinoic acid ( 5 ) were moderately active against three salmonella strains: Salmonella typhi , Salmonella enteritidis and Salmonella typhimirium , with minimum inhibition concentration values of 76.7 and 153.5 μM.

• #natural product bioactivities and synthesis
• #phytochemistry and biological activities
• #biological activity of diterpenoids and biflavonoids
• #ursolic acid

Synthesis and anticancer activity evaluation of some new 1,2,3,5-tetrazine derivatives attached to benzothiazole moiety

Joseph Tsemeugne, Yetiny Atuh Bah, Jean Paul Dzoyem, Jérôme N. Ndefongang, Ibukun M. Famuyide, Lyndy J. McGaw et 8 autre(s)

ARKIVOC

A series of novel tetrazine derivatives, containing benzothiazole framework, were prepared during the coupling reactions of some diazotized 2-aminobenzo[d]thiazole derivatives with p-acetaminophen. Their structures were elucidated based on NMR and MS spectrometry. The anticancer activity and the safety of the synthesized compounds along with the entire precursors were assessed against three human cancer cell lines and a normal cell line. All the synthesized compounds showed selective cytotoxic activity against the cancer cell lines used in comparison to the normal Vero cell line. Their IC50 values varied from 2.02 to 171.67 M.

• #synthesis and characterization of heterocyclic compounds
• #synthesis of tetrazole derivatives
• #synthesis and biological activity
• #benzothiazole

Two new secondary metabolites with antibacterial activities from Conyza aegyptiaca (Asteraceae)

Paul Etoga Mbarga, Hugues Fouotsa, Brigite Ndemangou, Julio Issah Mawouma Pagna, Ines Michèle Kanko Mbekou, Pierre Mkounga et 6 autre(s)

Natural Product Research

The bio guided fractionation of the dichloromethane/methanol (1:1) crude extract of the air-dried whole plant of C. aegyptiaca led to the isolation of one new flavone derivative designated conyflavone (1) and one new clerodane diterpene type designated conyclerodane (2) along with five known compounds including two flavonoids Gardenin C (3), chrysosplenetin (4) and two steroids glucoside of β-sitosterol (5), the mixture of stigmasterol (6) and β-sitosterol (6′) and ent-2b,18,19trihydroxycleroda-3,13-dien-16,15-olide (7). The structures were established by spectroscopic methods including IR, 1D and 2D NMR in conjunction with mass spectroscopy and by comparison to data of related compounds described in literature. The stereocentres in compound 2 were determined by SC-XRD analysis. Crude extract as well as fractions and pure compounds were evaluated in vitro for their antibacterial activities against four pathogenic and two clinical isolate strains using microdilution methods. Extracts and compounds displayed a moderate antibacterial activity with MIC values ranging from 125 to 500 µg/mL.

• #essential oils and antimicrobial activity
• #natural product bioactivities and synthesis
• #phytochemistry and biological activities
• #stigmasterol

Antibacterial activity of some chemical constituents from Trichilia prieuriana (Meliaceae)

Julio Issah Mawouma Pagna, Ines Michèle Kanko Mbekou, Armelle Tontsa Tsamo, Pierre Mkounga, Marcel Frese, Hans‐Georg Stammler et 4 autre(s)

Zeitschrift für Naturforschung B

Abstract The chemical study of hydroethanolic extracts from different parts of Trichilia prieuriana (Meliaceae) led to the isolation and identification of 22 compounds: 2 β ,3 β ,4 β -trihydroxypregnan-16-one ( 1 ), prieurianin ( 2 ), flindissone ( 3 ), deoxyflindissone ( 4 ), picraquassin E ( 5 ), ursolic acid ( 6 ), 3 β -acetoxy-11 α -hydroxyurs-12-en ( 7 ), 3 β -acetoxy-urs-12-en-11-one ( 8 ), 3 β -acetoxy- β -amyrin ( 9 ), friedelin-3-ol ( 10 ), 3-oxo, friedelin ( 11 ), 3-oxo, fridelin-28-ol ( 12 ), oleanolic acid ( 13 ), hederagenin ( 14 ), mixture of stigmasterol ( 15 ), β -sitosterol ( 16 ), β -sitosterol-3- O - β -glucopyranoside ( 17 ) and stigmasterol-3- O - β -glucopyranoside ( 18 ), erythrodiol ( 19 ), scopoletin ( 20 ), 4-hydroxy-3,5-dimethoxybenzoic acid ( 21 ) and shikimic acid ( 22 ). The absolute configurations and crystal structures of compounds 1 and 2 are reported herein for the first time. Crude extracts, fractions and isolated compounds were evaluated for their antibacterial activities against nine bacterial strains. Crude extracts from the root wood of T. prieuriana exhibited good antibacterial potency with minimal inhibitory concentration (MIC) values ranging from 31.25 to 500 µg mL −1 on the test bacteria. The ethyl acetate fraction from root wood and n -hexane-ethyl acetate (3:1) fraction from leaves showed a moderate antibacterial activity with MIC value of 250 μg mL −1 on all test bacteria. Isolated compounds exhibited significant antibacterial activity with MIC values ranging from 4.09 to 71.8 µ m . Compounds 3 , 6 and 7 were the most active with a broad spectrum of activities.

• #phytochemical compounds biological activities
• #natural product bioactivities and synthesis
• #marine sponges and natural products
• #friedelin

Antimycobacterial cycloartane derivatives from the roots of Trichilia welwistchii C. DC (Meliaceae)

Armelle Tontsa Tsamo, Edwige P. Fodja Saah, Moses K. Langat, Pierre Mkounga, Alain François Kamdem Waffo, Augustin Ephrem Nkengfack

Zeitschrift für Naturforschung B

Abstract Chemical investigation of the roots of Trichilia welwitschii yielded a cycloartane type terpenoid 28,29-bis-norcycloart-24-en-3 β ,4 α ,6 α -triol ( 1 ), isolated as pure compound for the first time, three coumarins and three sterols. New cycloartane derivatives ( 1a ) and ( 1b + 1c ) were obtained by hemi-synthetic reaction of compound 1 . The structures of 1a – c were established by spectroscopic methods including 1D and 2D-NMR analysis, HR-EIMS, chemical transformations and by comparison of these data with those of related compounds. Evaluated for their antimycobacterial potential, compound 1 and 1b + 1c were determined to show significant activities against Mycobacterium tuberculosis MIC values of 6.25 μg mL −1 while compound 1a displayed weak activity showing MIC &gt; 100 μg mL −1 . Compounds 2 – 4 displayed moderate activity with MIC values range from 12.5 to 50 μg mL −1 .

• #phytochemical compounds biological activities
• #natural product bioactivities and synthesis
• #traditional and medicinal uses of annonaceae
• #antimycobacterial

CCDC 2071433: Experimental Crystal Structure Determination

Patrice Kenfack Tsobnang, Tontsa, A. Tsamo, Yves A. Mbiangué, Pamela Kemda Nangmo, Saurelle Kenfack Tiofack, Pierre Mkounga et 2 autre(s)

The Cambridge Structural Database

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

• #crystallization and solubility studies
• #x-ray diffraction in crystallography
• #crystal structure
• #crystallography

CCDC 2071435: Experimental Crystal Structure Determination

Patrice Kenfack Tsobnang, Tontsa, A. Tsamo, Yves A. Mbiangué, Pamela Kemda Nangmo, Saurelle Kenfack Tiofack, Pierre Mkounga et 2 autre(s)

The Cambridge Structural Database

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

• #crystallization and solubility studies
• #x-ray diffraction in crystallography
• #crystallography
• #geography

Chemical constituents from Diospyros fragrans Gürke (Ebenaceae)

Nathalie S. Jouwa Tameye, Carine Mvot Akak, Georges Bellier Tabekoueng, Pierre Mkounga, Gabin Thierry M. Bitchagno, Bruno Ndjakou Lenta et 2 autre(s)

Biochemical Systematics and Ecology

• #natural product bioactivities and synthesis
• #bioactive compounds and antitumor agents
• #phytochemistry and biological activities
• #betulinic acid

Contributions of secondary alcohol–ketone O—H...O=C and furan–acetate C sp 2 —H...OOC synthons to the supramolecular packings of two bioactive molecules

Patrice Kenfack Tsobnang, Armelle Tontsa Tsamo, Yves A. Mbiangué, Pamela Kemda Nangmo, Saurelle Kenfack Tiofack, Pierre Mkounga et 2 autre(s)

Acta Crystallographica Section C Structural Chemistry

The crystal structures of rubescin D ( 1 , C 26 H 30 O 5 ) and monadelphin A ( 2 , C 30 H 36 O 11 ), bioactive molecules of the vilasinin and gedunin classes of limonoids, respectively, are reported for the first time and the synthons affecting their crystal packings are analyzed on the basis of their occurrences in molecules in the Cambridge Structural Database that share the same moieties. Rubescin D, 1 , crystallizes in the space group P 2 1 and its molecular structure consists of three six-membered rings A , C and D having, respectively, envelope, twist-boat and half-chair conformations, and three five-membered rings with half-chair ( B and E ) and planar conformations ( F ). Many synthons found in the crystal packing of 1 are in agreement with expectations derived from molecules displaying the same moieties. However, the secondary alcohol–ketone O—H...O=C synthon, which has a low occurrence (2.9%), contributes much to the layered packing, while the furan–ketone C sp 2 —H...O=C and secondary alcohol–epoxide O—H...OC 2 synthons usually found in these compounds (occurrences of 20.6 and 17.6%, respectively) are missing. The packing of 1 is close to that of ceramicine B ( 3 ), but is completely different from that of TS3 ( 4 ), suggesting that the absence of the epoxide group in 3 would have favoured the furan–secondary alcohol C sp 2 —H...OH synthon and that the missing hydroxy group in 4 , a strong hydrogen-bond donor, would have favoured the involvement of water molecules in the crystal packing. The molecular structure of monadelphin A, 2 , consists of four six-membered fused rings ( A , B , C and D ) and one five-membered ring ( E ); they have twist-boat ( A and C ), chair ( B ), screw-boat ( D ) and planar ( E ) conformations. The molecule crystallizes in the space group P 2 1 2 1 2 1 with the contribution of many synthons usually found in compounds having the same moieties. However, the secondary alcohol–acetate O—H...OOC and secondary alcohol–ketone O—H...O=C synthons (occurrences of 16.7% each in these compounds) are missing. The furan–acetate C sp 2 —H...OOC synthon not observed in these compounds greatly contributes to the layered packing of 2 . The layered packing is very close to those of 7-oxogedunin ( 5 ) and 6-dehydro-7-deacetoxy-7-oxogedunin ( 6 ), which both crystallize in the space group P 2 1 .

• #phytochemical compounds biological activities
• #natural product bioactivities and synthesis
• #phytochemistry and bioactivity studies
• #synthon

Inhibitory activity of limonoids from Khaya grandifoliola C.DC (Meliaceae) against hepatitis C virus infection in vitro .

Arnaud Fondjo Kouam, Frédéric Nico Njayou, Fei Yuan, Babayemi Olawale Oladejo, He Hongtao, Pierre Mkounga et 1 autre(s)

PubMed

OBJECTIVE: has recently been shown to inhibit hepatitis C virus (HCV) infection and three limonoids (17-epi-methyl-6-hydroxylangolensate, 7-deacetoxy-7-oxogedunin and 7-deacetoxy-7R-hydroxygedunin) were purified from this fraction. The present study aimed at assessing the inhibitory effect of these limonoids on HCV using cell-culture derived HCV (HCVcc) system. MATERIALS AND METHODS: luciferase reporter gene to rescue the HCVcc particles which were used to infect naïve cells in the presence or absence of the studied limonoids during 72 hr. Infection and replication rates were monitored by luciferase reporter assay and immunofluorescence assay (IFA) while cellular gene expression was analyzed by western blot, respectively. RESULTS: The limonoids inhibited HCV infection mostly by targeting entry and replication stage. Their inhibitory effect on entry step, comparable to that of anti-CD81 antibody, was related to the blocking of CD81 receptor. In the replication step, the limonoids decreased the expression of NS5B similar to danoprevir. These compounds also significantly decreased but up-regulated the expression of Class-III phosphatidylinositol 4-kinase alpha and 2',5'-oligoadenylate synthase-3, respectively. CONCLUSION: are potential anti-HCV agents and may offer an advantage in the treatment of HCV infection.

• #phytochemical compounds biological activities
• #phytochemistry and bioactivity studies
• #beetle biology and toxicology studies
• #hepatitis c virus

Pyrrovobasine, hybrid alkylated pyrraline monoterpene indole alkaloid pseudodimer discovered using a combination of mass spectral and NMR-based machine learning annotations

Hugues Fouotsa, Pierre Mkounga, Alain Méli Lannang, Jérôme Vanheuverzwijn, Zhiyu Zhou, Karine Leblanc et 8 autre(s)

Organic & Biomolecular Chemistry

-guided phytochemical investigation led to its isolation. Its structure was formally established based on HRMS, 1D/2D NMR data, and the application of the tool Small Molecule Accurate Recognition Technology (SMART 2.0). Its absolute configuration was assigned by the exciton chirality method and TD-DFT ECD calculations. Besides featuring an unprecedented intermonomeric linkage in the small group of vobasine/tryptamine hybrids, pyrrovobasine also represents the first pyrraline-containing representative in the whole monoterpene indole alkaloids group. Biosynthetic hypotheses possibly underpinning these structural oddities are proposed here.

• #alkaloids: synthesis and pharmacology
• #traditional and medicinal uses of annonaceae
• #berberine and alkaloids research
• #chemistry

Synthesis, characteristic fragmentation patterns, and antibacterial activity of new azo compounds from the coupling reaction of diazobenzothiazole ions and acetaminophen

Joseph Tsemeugne, Pamela Kemda Nangmo, Pierre Mkounga, Jean‐De‐Dieu Tamokou, Iréne Chinda Kengne, Giles Edwards et 2 autre(s)

Heterocyclic Communications

Abstract In this study, a series of azobenzothiazole dyes 4 were synthesized via diazotization of substituted benzothiazole derivatives followed by azo coupling with acetaminophen. The chemical structures of all synthesized compounds were confirmed using analytical data and spectroscopic techniques, including UV-visible, IR, mass spectra, and 1 H- and 13 C-NMR. The in situ formed diazobenzothiazole ions regiospecifically react with acetaminophen derivatives in the Hollemann-guided electrophilic aromatic substitution mechanism. The regio-orientations were established, on the one hand, by a rigorous interpretation of 1 H-NMR spectra and, on the other hand, by the characteristic fragmentation patterns observed on the electrospray mass spectra. In the cases of 4a and 4b, multisubstitutions occurred. The antimicrobial activity of compound 4 , along with all the starting materials, was investigated on Pseudomonas aeruginosa PA01, Staphylococcus aureus 18, Escherichia coli 64R, and S. aureus ATCC 25923. The results showed that this skeletal framework exhibited marked potency as antibacterial agents. The most active antibacterial agent against both targeted organisms was compound 4a′ .

• #synthesis and biological activity
• #synthesis and characterization of heterocyclic compounds
• #synthesis of tetrazole derivatives
• #chemistry

Voatriafricanines A and B, Trimeric Vobasine-Aspidosperma-Aspidosperma Alkaloids from Voacanga africana

Hugues Fouotsa, Pierre Le Pogam, Pierre Mkounga, Alain Méli Lannang, Guillaume Bernadat, Jérôme Vanheuverzwijn et 9 autre(s)

Journal of Natural Products

Voatriafricanines A and B ( 1 and 2 ), the first examples of vobasine-aspidosperma-aspidosperma monoterpene trisindole alkaloids, were isolated from the stem barks of Voacanga africana, guided by a molecular networking strategy. Their structures, including absolute configurations, were elucidated by spectroscopic methods and ECD calculations. Compounds 1 and 2 possess intramolecular hydrogen bonding, sufficiently robust to transfer homonuclear and heteronuclear magnetizations. Compound 1 exhibited potent antimycobacterial activity with no discernible cytotoxic activity.

• #alkaloids: synthesis and pharmacology
• #traditional and medicinal uses of annonaceae
• #plant and fungal species descriptions
• #aspidosperma

An Antibacterial Isovaleronitrile Diglycoside From Detarium microcarpum Guill. Perr. ( Fabaceae )

William F. Feudjou, Arnaud M. Mbock, Marlyse B. W. Ouahouo, Valérie Tedjon Sielinou, Racéline Kamkumo Gounoue, Pierre Mkounga et 5 autre(s)

Sage Journals Data

A new isovaleronitrile diglycoside, named microcarposide (<b>1</b>), together with 6 known compounds: lupeol (<b>2</b>), betulinic acid (<b>3</b>), β-sitosterol glucoside (<b>4</b>), methyl gallate (<b>5</b>), luteolin (<b>6</b>), and epicatechin (<b>7</b>), was isolated from the methanolic extract of the fruits of <i>Detarium microcarpum</i> Guill. Perr. The structures of the compounds were determined by extensive analysis of 1D- and 2D-¹H and ¹³C NMR spectroscopic data in conjunction with mass spectrometry and by comparison with data reported in the literature. Compound <b>1</b> was characterized as (2<i>R</i>)-2-[(6″-<i>O-</i>β-l-rhamnopyranosyl-β-d-glucopyranosyl)oxy]-3-methylbutanenitrile. Some of the isolated compounds were evaluated for their antibacterial activities against several microorganisms; only compound <b>1</b> was active against <i>Salmonella typhi</i>, <i>Salmonella enteritidis</i>, and <i>Salmonella typhimurium</i> with minimum inhibition concentration values of 153.4, 76.7, and 76.7 μM, respectively.

• #natural product bioactivities and synthesis
• #ethnobotanical and medicinal plants studies
• #natural antidiabetic agents studies
• #fabaceae

Heterophynone and methyl ester of Colic acid, two new compounds with antimicrobial activity from Cola heterophylla (Sterculiaceae)

Martin Mbané Noah, Maurice Tagatsing Fotsing, Alex de Théodore Atchadé, Pierre Mkounga, Fabrice Fekam Boyom, Emmanuel Talla et 2 autre(s)

Natural Product Research

The ethyl acetate fraction, the stem bark and the residual methanolic extracts from the leaves of Cola heterophylla (Sterculiaceae) led to the isolation of two new compounds: Heterophynone (1) and methyl ester of Colic acid (6), along with four known triterpenes: betulinic acid (2), oleanolic acid (3), ursolic acid (4) and chletric acid (5). Structures of compounds were established by different spectroscopic methods that included 1D and 2D NMR experiment. The antimicrobial activity of isolated compounds was evaluated against two yeasts, Candida Albicans NR 29456 and Candida Krusei 1415; and five Gram-positive bacterial, Salmonella enteric Serovar Muenchem, Salmonella enteric Serovar Thyphimurium, Staphylococcus aureus NR 46003, Staphylococcus aureus NR46374 and Pseudomonas aeruginosa HM 601). Among tested compounds, Heterophynone was found to be the most active with significant antimicrobial activity against Salmonella enteric Serovar Thyphimurium (MIC = 7.82 μg/mL and MBC = 62.5 μg/mL) and good activity against Candida Albicans NR 29456 (MIC = 62.5 μg/mL).

• #essential oils and antimicrobial activity
• #natural product bioactivities and synthesis
• #plant pathogenic bacteria studies
• #antimicrobial

Selective cytotoxic activity of isolated compounds from Globimetula dinklagei and Phragmanthera capitata (Loranthaceae)

Emmanuel Mfotie Njoya, Hermine L.D. Maza, Pierre Mkounga, Ulrich Koert, Augustin E. Nkengfack, Lyndy J. McGaw

Zeitschrift für Naturforschung C

This study aimed to evaluate the selective cytotoxicity of six natural compounds on four cancerous cells (MCF-7, HeLa, Caco-2 and A549) and two normal intestinal and lung cells (Hs1.Int and Wl-38) cells. We also attempted to analyze basically the structure-activity relationships and to understand the mechanism of action of active compounds using the Caspase-Glo® 3/7 kit. Globimetulin B (2) isolated from Globimetula dinklagei was significantly cytotoxic on cancerous cells with 50% inhibitory concentrations (IC50) ranging from 12.75 to 37.65 μM and the selectivity index (SI) values varying between 1.13 and 3.48 against both normal cells. The compound 3-O-β-d-glucopyranosyl-28-hydroxy-α-amyrin (5) isolated from Phragmanthera capitata exhibited the highest cytotoxic activity on HeLa cells with the IC50 of 6.88 μM and the SI of 5.20 and 8.71 against Hs1.Int and Wl-38 cells, respectively. A hydroxyl group at C-3 of compounds was suggested as playing an important role in the cytotoxic activity. The induction of caspase-3 and -7 activity represents some proof that apoptosis has occurred in treated cells. Globimetulin B (2) selectively killed cancer cells with less toxicity to non-cancerous cells as compared to conventional doxorubicin therapy.

• #phytochemistry and biological activities
• #bioactive compounds and antitumor agents
• #natural product bioactivities and synthesis
• #hela

Electronic Structure, Spectroscopic (IR, Raman, UV-Vis, NMR), Optoelectronic, and NLO Properties Investigations of Rubescin E (C 31 H 36 O 7 ) Molecule in Gas Phase and Chloroform Solution Using Ab Initio and DFT Methods

R.A. Yossa Kamsi, Geh Wilson Ejuh, Tchoffo Fidele, Pierre Mkounga, J.M.B. Ndjaka

Advances in Condensed Matter Physics

Quantum chemical methods were used to study the electronic structure and some physicochemical properties of Rubescin E molecule. Good agreement with experiment was found for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msub><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">J</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn mathvariant="normal">3</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow><mml:mrow><mml:mi mathvariant="normal">H</mml:mi><mml:mtext>-</mml:mtext><mml:mi mathvariant="normal">H</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> coupling constant, IR, 1 H NMR, and 13 C NMR. The excitation energy and oscillator strength calculated by TD-DFT also complement with experiment. Large values were obtained for dipole moment, polarizability, first static hyperpolarizability, electric susceptibility, refractive index, and dielectric constant, meaning that Rubescin E has strong optical and phonon application and can be a good candidate as NLOs material. The 3D analysis of the title molecule leads us to the conclusion that electron can easily be transferred from furan to tetrahydrofuran ring. The global reactivity descriptors were evaluated. Mulliken, ESP, and NBO charges comparisons were carried out and described.

• #nonlinear optical materials research
• #metal complexes synthesis and properties
• #inorganic and organometallic chemistry
• #materials science

Rubescins F–H, new vilasinin-type limonoids from the leaves of Trichilia rubescens (Meliaceae)

Armelle Tontsa Tsamo, Julio Issah Mawouma Pagna, Pamela Kemda Nangmo, Pierre Mkounga, Hartmut Laatsch, Augustin Ephrem Nkengfack

Zeitschrift für Naturforschung C

Three new limonoids, designated as rubescins F (1), G (2), and H (3), together with two known compounds of this type, TS1 (4) and trichirubine A (5), were isolated from methylene chloride/methanol extracts of Trichilia rubescens leaves. The structures of these compounds were elucidated based on 1D and 2D nuclear magnetic resonance (NMR) analysis and complemented by electrospray ionization high-resolution mass spectrometry results and by comparison to data of related compounds described in the literature and ab initio calculations. Rubescin F (1) is the first limonoid from Trichilia spp. with an oxetane ring between C-7 and C-14, which seems to be formed by the isomerization of TS1 (4). The γ-hydroxybutenolide rubescin G (2) is a potential precursor of trichirubine A (5), whereas rubescin H (3) is the first example of a triterpenoid with a single bond between C-7/C-14, forming a cyclopropane ring. The absolute configuration of these limonoids was derived from biosynthetic considerations and ab initio calculations of NMR and optical rotation dispersion data.

• #phytochemical compounds biological activities
• #chemistry
• #limonoid
• #stereochemistry

Study of the molecular structure, electronic and chemical properties of Rubescin D molecule

R.A. Yossa Kamsi, Geh Wilson Ejuh, Pierre Mkounga, J.M.B. Ndjaka

Chinese Journal of Physics

• #nonlinear optical materials research
• #advanced chemical physics studies
• #nonlinear optical materials studies
• #hyperpolarizability

Oligoamide, a new lactam from the leaves of Angylocalyx oligophyllus

Brussine Nadège Kweka Wakeu, Jean‐Bosco Jouda, Gertrude Foudjo Melacheu, Lazare Sidjui Sidjui, Pierre Mkounga, Mehreen Lateef et 3 autre(s)

Natural Product Research

A new lactam, oligoamide (1), along with three known compounds (2–4), stigmasterol-3-O-β-D-glucopyranoside (2), formononetin (3) and (-)-pinitol (4) were isolated from the CH2Cl2/CH3OH (1:1) extract of the leaves of Angylocalyx oligophyllus by chromatographic separation. Their structures were elucidated on the basis of spectroscopic analysis (UV, IR, MS, 1D, and 2D NMR). Compound 1 was found to have weak antioxidant and urease inhibitory potential.

• #phytochemical compounds biological activities
• #natural product bioactivities and synthesis
• #phytochemistry and bioactive compounds
• #stigmasterol

Rubescins I and J, further limonoid derivatives from the stem bark of Trichilia rubescens (Meliaceae)

Armelle Tontsa Tsamo, Raduis Melong, Pierre Mkounga, Augustin Ephrem Nkengfack

Natural Product Research

Two new tetranorterpenoid derivatives named rubescins I (1) and J (2), were isolated along with six known compounds including rubescin D (3), lichexanthone (4), scopoletin (5), scopoletin O-glycoside (6), β-sitosterol (7) and stigmasterol (8) from the stem bark of Trichilia rubescens (Meliaceae). The structures of the compounds were determined by means of MS, different NMR and by comparison with related data reported in the literature.

• #phytochemical compounds biological activities
• #meliaceae
• #scopoletin
• #limonoid

Two new indolic and quinolinic alkaloids and other secondary metabolites from Mostuea thomsonii (Loganiaceae)

Eric Gustave Bobda Gompe, Blandine Marlyse Wache Ouahouo, Valérie Tedjon Sielinou, Maurice Tsaffack, Jean Fotie, Jules Clément Nguedia Assob et 3 autre(s)

Phytochemistry Letters

• #traditional and medicinal uses of annonaceae
• #alkaloids: synthesis and pharmacology
• #natural product bioactivities and synthesis
• #chemistry

Chemical constituents from leaves and root bark of Trichilia monadelpha (Meliaceae)

Kemda Pamela Nangmo, Tontsa Armelle Tsamo, Zhen Liu, Pierre Mkounga, Sergi Hervé Akoné, Nolé Tsabang et 4 autre(s)

Phytochemistry Letters

• #phytochemical compounds biological activities
• #insect pest control strategies
• #meliaceae
• #limonoid

Kostchyienones A and B, new antiplasmodial and cytotoxicity of limonoids from the roots of Pseudocedrela kotschyi (Schweinf.) Harms

Lazare Sidjui Sidjui, Yves Oscar Ditchou Nganso, Rufin Marie Kouipou Toghueo, Brussine Nadège Kweka Wakeu, Joel T. Dameue, Pierre Mkounga et 4 autre(s)

Zeitschrift für Naturforschung C

Two new limonoids, kostchyienones A (1) and B (2), along with 12 known compounds 3-14 were isolated from the roots of Pseudocedrela kostchyi. Compound (7) was isolated for the first time from a natural source. Their structures were elucidated on the basis of spectroscopic evidence. Compounds 1-6 and 13-14 gave IC50 values ranging from 0.75 to 5.62 μg/mL for antiplasmodial activity against chloroquine-sensitive (Pf3D7) and chloroquine-resistant (PfINDO) strains of Plasmodium falciparum. Compound 5 showed moderate potential cytotoxicity against the HEK239T cell line with an IC50 value of 22.2±0.89 μg/mL. The antiplasmodial efficacy of the isolated compounds supports the medicinal value of this plant and its potential to provide novel antimalarial drugs.

• #phytochemical compounds biological activities
• #traditional and medicinal uses of annonaceae
• #phytochemistry and bioactivity studies
• #cytotoxicity

Phytochemical analysis with free radical scavenging, nitric oxide inhibition and antiproliferative activity of Sarcocephalus pobeguinii extracts

Emmanuel Mfotie Njoya, Aristide Mfifen Munvera, Pierre Mkounga, Augustin Ephrem Nkengfack, Lyndy J. McGaw

BMC Complementary and Alternative Medicine

Free radicals have been implicated in the pathogenesis of diverse metabolic disorders including cancer. Therefore, fighting against free radicals has become an important strategy in the prevention or treatment of such diseases, in addition to direct or indirect anticancer chemotherapy. Sarcocephalus pobeguinii has been used traditionally to treat various diseases in which excess production of free radicals is implicated, warranting investigation of its free radical scavenging, anticancer and anti-inflammatory activity. In the present study, extracts from leaves, fruits, roots and bark of Sarcocephalus pobeguinii were evaluated on four human cancer cell lines (MCF-7, HeLa, Caco-2 and A549 cells) and a non-cancerous cell line for their antiproliferative potential. The cells were incubated with the plant extracts for 48 h at 37 °C in a 5% CO 2 humidified environment and their cytotoxic effect was determined using the tetrazolium-based colorimetric (MTT) assay. The radical inhibition was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging techniques. The nitric oxide inhibitory activity was determined using LPS-activated RAW 264.7 macrophages. The correlation between radical scavenging capacity and antiproliferative activity was also analysed. The extract from leaves of Sarcocephalus pobeguinii (LSP) exhibited the highest cytotoxic effect on all four of the human cancer cell lines but with some cytotoxicity to the normal Vero cells. However, the LSP extract had the best selectivity index, ranging from 3.15 to 18.28. Also, antioxidant and anti-inflammatory assays indicated that the LSP extract had the highest radical scavenging capacity of all the extracts. A positive linear correlation was found between free radical scavenging ability and antiproliferative activity against the four cancer cell lines, with the highest correlation factor (R 2 = 0.9914) obtained between DPPH inhibition and antiproliferative activity against A549 cells. The high selectivity index of the Sarcocephalus pobeguinii leaf extract indicates the potential of using this extract in cancer therapy. Furthermore, the positive correlation between free radical scavenging and antiproliferative activity suggests that the radical scavenging capacity of extracts may contribute to a prediction of their anticancer property.

• #phytochemicals and antioxidant activities
• #plant-derived bioactive compounds
• #natural product bioactivities and synthesis
• #hela

Tapinanthus bangwensisの種子からのトリテルペノイド【Powered by NICT】

Maza Hermine, Pierre Mkounga, Fenkam Sandra Larissa, Sado Sylvain Kamdem, Ishikawa Hayato, Hiroshi Nishino et 1 autre(s)

Phytochemistry Letters

• #healthcare and venom research
• #aeronautics
• #engineering

New lupan-type triterpenoids

Pierre Mkounga, Hermine L.D. Maza, Blandine Marlyse Wache Ouahouo, Lydie N. Tyon, Hayato Ishikawa, Hiroshi Nishino et 1 autre(s)

Zeitschrift für Naturforschung C

Three new lupan-type triterpernoid derivatives, namely globimetulin A (1), B (2) and C (3), were isolated from the shoot of Globimetula dinklagei (Loranthaceae), a hemiparasitic plant growing on Manihot esculenta, along with five known compounds: friedelin (4), friedelan-3-ol (5), 28-hydroxyfriedelin (6), 4-hydroxy-3,5-dimethoxybenzoic acid (7) and (1R,5S,7S)-7-[2-(4-hydroxyphenyl)ethyl]-2,6-dioxabicyclo[3.3.1]nonan-3-one (8). The structures of the new compounds were elucidated by detailed analyses of their MS, IR, 1D and 2D NMR spectral data and chemical evidence. Some of these compounds were evaluated in vitro for their antimicrobial activities against a wide range of microorganisms, but none of them exhibited noticeable activity.

• #natural product bioactivities and synthesis
• #plant biochemistry and biosynthesis
• #pharmacological effects of natural compounds
• #triterpenoid

The Limonoids TS3 and Rubescin E Induce Apoptosis in Human Hepatoma Cell Lines and Interfere with NF-κB Signaling

Nicole Lange, Armelle Tontsa Tsamo, Claudia Wegscheid, Pierre Mkounga, Augustin Ephrem Nkengfack, C Loscher et 2 autre(s)

PLoS ONE

Hepatocellular carcinoma (HCC) is extremely resistant towards pharmacological therapy. To date, the multi-kinase inhibitor Sorafenib is the only available therapeutic agent with the potential to prolong patient survival. Using the human hepatoma cell lines HepG2 and Huh7, we analyzed anti-cancer activities of 6 purified havanensin type limonoids isolated from the traditional African medicinal plant Trichilia rubescens Oliv. Our results show that two of the compounds, TR4 (TS3) and TR9 (Rubescin E) reduced hepatoma cell viability, but not primary hepatocyte viability, at TC50s of 5 to 10 μM. These were significantly lower than the TC50s for Sorafenib, the histone deacetylase inhibitor SAHA or 5-Fluoruracil. In comparison, TR3 (Rubescin D), a limonoid isolated in parallel and structurally highly similar to TR4 and TR9, did not interfere with hepatoma cell viability. Both, TR4 and TR9, but not TR3, induced apoptosis in hepatoma cells and interfered with NF-κB activation. TR4 as well as TR9 significantly supported anti-cancer activities of Sorafenib. In summary, the limonoids TR4 and TR9 exhibit anti-cancer activities and support Sorafenib effects in vitro, having the potential to support future HCC therapy.

• #phytochemical compounds biological activities
• #natural compounds in disease treatment
• #natural product bioactivities and synthesis
• #sorafenib

Triterpenoids from seeds of Tapinanthus bangwensis

Hermine L.D. Maza, Pierre Mkounga, Sandra Larissa Fenkam, Sylvain Kamdem Sado, Hayato Ishikawa, Hiroshi Nishino et 1 autre(s)

Phytochemistry Letters

• #natural product bioactivities and synthesis
• #plant biochemistry and biosynthesis
• #phytochemistry and biological activities
• #oleanane

Plant extracts from Cameroonian medicinal plants strongly inhibit hepatitis C virus infection in vitro

Borris Rosnay Galani Tietcheu, Marie-Emmanuelle Sahuc, Frédéric Nico Njayou, Gaspard Deloison, Pierre Mkounga, William F. Feudjou et 5 autre(s)

Frontiers in Microbiology

According to some recent studies, Cameroon is one of the sub-Saharan African countries most affected by hepatitis C, with low access to the standard therapy based on the combination of pegylated interferon and ribavirin. A first ethnobotanical survey, conducted in the Western region of Cameroon, reported the use of several medicinal plants in traditional medicine for the healing of liver-related disorders. Crude organic extracts of five plants surveyed were prepared and their effect against hepatitis C virus (HCV) infection investigated. The HCV JFH1 strain cell culture system HCVcc was used. The antiviral activity was quantified by immunofluorescent labeling of HCV E1 envelope protein at 30 h post-infection in the presence of the plant extracts. Active compounds were then tested in time course infection experiments. Dose-response and cellular toxicity assays were also determined. Three extracts, methanol extracts from roots of Trichilia dregeana, stems of Detarium microcarpum and leaves of Phragmanthera capitata, showed anti-HCV activity, with half-maximal inhibitory concentration of 16.16, 1.42, and 13.17 μg/mL, respectively. Huh-7 cells were incubated with the extracts for 72 h and it appears that T. dregeana extract is not toxic up to 200 μg/mL, D. microcarpum up to 100 μg/mL and P. capitata up to 800 μg/mL. All the three extracts showed a strong inhibition of HCV entry and no effect on replication or secretion. Taken together, these results showed that extracts from Cameroonian medicinal plants are promising sources of anti-HCV agents.

• #hepatitis c virus research
• #hepatitis b virus studies
• #liver disease diagnosis and treatment
• #medicinal plants

Terpenoids from the stem bark of Neoboutonia macrocalyx (Euphorbiaceae)

Timoleon Maffo, Pascal Wafo, Ramsay S.T. Kamdem, Raduis Melong, Philip F. Uzor, Pierre Mkounga et 2 autre(s)

Phytochemistry Letters

• #traditional and medicinal uses of annonaceae
• #natural product bioactivities and synthesis
• #plant biochemistry and biosynthesis
• #euphorbiaceae

ChemInform Abstract: Rubescins A (I), B (II) and C (III): New Havanensin Type Limonoids from Root Bark of Trichilia rubescens (Meliaceae).

Armelle Tontsa Tsamo, Pierre Mkounga, Frédéric Nico Njayou, José E. Manautou, Kirk Marat, Philip G. Hultin et 1 autre(s)

ChemInform

Abstract Title compounds are isolated from the root bark of Trichilia rubescens (Meliaceae) together with 3 known compounds.

• #phytochemical compounds biological activities
• #meliaceae
• #chemistry
• #bark (sound)

Rubescins A, B and C: New Havanensin Type Limonoids from Root Bark of &lt;i&gt;Trichilia rubescens&lt;/i&gt; (Meliaceae)

Armelle Tontsa Tsamo, Pierre Mkounga, Frédéric Nico Njayou, José E. Manautou, Kirk Marat, Philip G. Hultin et 1 autre(s)

Chemical and Pharmaceutical Bulletin

Three new limonoids, rubescins A-C (1-3), and three known compounds including, havanensin type limonoid TS3 (4), β-sitosterol, and stigmasterol were isolated from the root bark of Trichilia rubescens. Their structures were elucidated by means of extensive spectroscopic analyses, particularly one dimensional (1D)- and 2D-NMR techniques in conjunction with mass spectrometry. Rubescins A-C (1-3) and limonoid TS3 (4) were evaluated for their protective effects against oxidative stress induced in HC-04 cells by H2O2. Compound (1) showed strong inhibitory effects on lactase dehydrogenase (LDH) leakage, being as active (IC50 value of 0.0026 µM) as the positive control quercetin (IC50 value of 0.0030 µM).

• #phytochemical compounds biological activities
• #moringa oleifera research and applications
• #seaweed-derived bioactive compounds
• #limonoid

Pycnanthulignenes A−D, Antimicrobial Cyclolignene Derivatives from the Roots of Pycnanthus angolensis

Eric Carly Nono Nono, Pierre Mkounga, Victor Kuete, Kirk Marat, Philip G. Hultin, Augustin E. Nkengfack

Journal of Natural Products

Investigation of the constituents of Pycnanthus angolensis roots has resulted in the isolation of four new cyclolignene derivatives, named pycnanthulignene A (1), pycnanthulignene B (2), pycnanthulignene C (3), and pycnanthulignene D (4), and six known compounds, 4,5-dimethoxy-3',4'-methylenedioxy-2,7'-cycloligna-7,7'-diene, 2,7-dimethoxy-3,6-dimethylnaphthalene, 4'-methoxy-4,5-methylenedioxy-2,7'-cyclolign-7-ene, genkwainin, 8-hydroxykanzakiflavone-2, and formononetin. The structures of these compounds were established using spectroscopic methods. Compounds 1 and 3 showed significant antimicrobial activities against a panel of drug-resistant pathogens.

• #phytochemical compounds biological activities
• #phytochemistry and biological activities
• #traditional and medicinal uses of annonaceae
• #antimicrobial

Triterpenoid Derivatives from Cylicodiscus gabunensis

Pierre Mkounga, Alembert Tiabou Tchinda, Jacques Kouam

Chemical and Pharmaceutical Bulletin

Three new olean-12-ene derivatives (1-3), together with known urs-12-ene-3beta, 28-diol (4) were isolated from the stem root of Cylicodiscus gabunensis. The structures of the new compounds were established by chemical and spectroscopic means as beta-amyrin-n-nonyl ether (1), 22alpha-hydroxyolean-12-en-3beta-yl-beta-D-galactopyranoside (2), and 24-hydroxyolean-12-en-3beta-yl-beta-D-glucopyranoside (3).

• #natural product bioactivities and synthesis
• #phytochemical compounds biological activities
• #phytochemistry and biological activities
• #chemistry