Search

Introduction The genus Quassia is a promising source of secondary metabolites with biological potential including antimalarial and cytotoxic activities. Limited data are available on the phytochemistry and pharmacology of Quassia silvestris Cheek & Jongkind, a Cameroonian medicinal plant used to treat various ailments. Objectives To carry out the bioassay-guided fractionation and LC-HR-ESI-MS analyses of the leaves extract from Q. silvestris; to purify the active fractions and isolate the major compounds using different chromatographic and spectroscopic methods. The obtained compounds will be evaluated for their biological activity. Material and methods Following the cytotoxic screening and LC-HR-ESI-MS profiling of fractions obtained from partition of the methanolic extract of Q. silvestris leaves, the CH2Cl2-soluble fraction which exhibited the highest cytotoxicity was retained for further investigations. Results Sixteen squalene-derived metabolites were identified with oxasqualenoid derivatives being the most predominant. Among the isolates, structure elucidation of two new oxasqualenoids quassiols E (1) and F (2), were achieved by NMR (one-dimensional (1D) and two-dimensional (2D)) and MS methods. The newly characterised compounds 1 and 2, together with the known tetraol (3) and 3-oxo-oleanoic acid (16) displayed moderate cytotoxicity. Conclusion The identification and structural characterisation of highly oxidised squalene derived metabolites from this plant may provide important insight data for further pharmacological investigations. The LC-HR-ESI-MSn method reported here could be developed as a rapid and efficient tool for the analyses of structurally related compounds in the genera Quassia, Simarouba, and Eurycoma of the subfamily Simarouboideae. Copyright © 2016 John Wiley & Sons, Ltd.

Resume L'etude phytochimique de l'extrait au dichloromethane des ecorces du tronc Vitex thyrsiflora Baker (Verbenaceae) a permis d'isoler six composes identifies a l'acide 20(R),24(E)-3-oxo-9β-lanosta-7,24-dien-26-oique (1), α-amyrine (2), β-amyrine (3), friedeline (4), au palmitate de β-sitosterol (5) et au glucoside de β'-sitosterol (6). Tous ces composes ont ete isoles pour la premiere fois de cette plante. Leurs structures ont ete elucidees sur la base de leurs donnees spectroscopiques et par comparaison avec celles de la litterature. Le compose 5 a presente une activite antiplasmodiale significative avec des CI50 de 3,09 et 8,98 μg/mL, contre les souches multi-resistantes Dd2 et K1 de P. falciparum, tandis que celle des composes 1 et 4 etait moderee. Toutes les molecules testees ont ete non cytotoxiques sur la souche de cellule epitheliale de singe (LLC-MK2). Les resultats obtenus peuvent justifier l'utilisation traditionnelle des ecorces du tronc de Vitex thyrsiflora dans le traitement du paludisme.

One new cerebroside derivative, namely liebrechtsianoside A (1), along with five known compounds: tetracosanoic acid (2), swertiaperennin (3), decussatin (4), swertianin (5) and β-sitosterol glucoside (6) were isolated from the the stem bark of Anthocleista liebrechtsiana . Their structures were elucidated by interpretation of NMR and MS data, and by comparison of these data with those reported in literature. Compound 1 showed the highest antiplasmodial activity against Dd2 chloroquine-resistant strain of Plasmodium falciparum.

Bioassay guided fractionation of Hypericum riparium leaves extract has resulted in the isolation and characterization of three new compounds namely chipericumin E (1), hyperenone C (3), and hyperixanthone (5), together with twenty known compounds. Their structures were elucidated based on comprehensive interpretation of spectroscopic and spectrometric data. Compounds 1-4, and 6-8 displayed moderate antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and cytotoxic effects on the human gastric cell line BGC-823 with IC50 values ranging from 6.54 to 18.50μM.

Chemical investigation of the methanol extract of the leaves of Tectona grandis led to the isolation of one new anthraquinone derivative, grandiquinone A (3-acetoxy-8-hydroxy-2-methylanthraquinone) (1), along with nine known compounds: 5,8-dihydroxy-2-methylanthraquinone (2), hydroxysesamone (3), 3-hydroxy-2-methylanthraquinone (4), quinizarine (5), betulinic acid (6), ursolic acid (7), tectograndone (8), corosolic acid (9) and sitosterol 3-O-b-D-glucopyranoside (10). Compounds 2 and 3 were isolated for the first time from the leaves of this plant, while 5 has never been reported from the genus Tectona. Hydroxysesamone (3) and tectograndone (8) were subjected to cyclisation and acetylation reactions to afford two hemisynthetic derivatives, 6,9-dihydroxy-2,2-(dimethyldihydropyrano)-3,4-dihydro-2Hbenzo[g] chromene-5,10-dione (11) and acetyltectograndone (12) respectively, which are reported here for the first time. The ethyl acetate-soluble portion, some of the isolated compounds and hemisynthetic derivatives were evaluated for their antiplasmodial activity against the multidrug-resistant Dd2 strain of Plasmodium falciparum. Compound 3 showed a prominent activity, while 2, 8, 9, 11 and 12 showed significant in vitro anti-malarial activity. Compound 1 was weakly active in this test. The structures of the compounds were elucidated by spectroscopic methods and comparison of the data with the literature. (C) 2014 Phytochemical Society of Europe. Published by Elsevier B. V. All rights reserved.

Two new anthraquinone dimers, schimperiquinones A (1) and B (2), together with the known 2-hydroxymethylanthraquinone (3), cleomiscosin A (4), oleanolic acid (5) and sitosterol 3-O-beta-D-glucoside (6) were isolated from the stem bark of Pentas schimperi. Their structures were elucidated on the basis of spectroscopic analysis and comparison with published data or by comparison with authentic samples. To the best of our knowledge, it is the first report of cleomiscosin A, a coumarinolignan from the genus Pentas. Compound 2 exhibited in vitro cytotoxicity (IC50 = 33.05 mu M) against the human cancer cell the BGC-823. (c) 2014 Phytochemical Society of Europe. Published by Elsevier B. V. All rights reserved.

An investigation of MeOH extract of Embelia schimperi stem led to the isolation of a new resorcinol derivative, 5-(7’Z-pentadecenyl)resorcinol (1), along with the known compounds lupeol (2) and β-sitosterol glucoside (3). The structures of isolated compounds were elucidated using spectroscopic methods. Compound 1 exhibited moderate in vitro cytotoxic activity against human Hela cell line.

A new prenylated xanthone, butyraxanthone F (1) together with 20 known compounds were isolated from the leaves of Pentadesma butyracea. Their identification was achieved by spectroscopic means and comparison of the data with literature or by direct comparison on TLC with authentic samples. To the best of our knowledge, this is the first report of 2-hydroxy-2,3-dihydrosqualene (17) from a natural source. Compounds 2-6 and 11-16 were found for the first time in this genus. The antiproliferative activity of the crude extract, fractions and some isolated compounds was evaluated against three human cancer cell lines, BGC-823, Hela and A549. The crude extract, fractions B and C showed weak activities. Globuxanthone (2) and 30-epi-cambogin (7) were found to be the most active compounds on the three cancer cells. The effect of 2 on Hela cells and that of 7 on BGC-823 cells were noteworthy. The antiproliferative potential of allanxanthone A (3), ergosta-4,6,8(14),22-tetraen-3-one (14) and 2-hydroxy-2,3-dihydrosqualene (17) against BGC-823 and Hela cells could be classified as moderate-to-weak. (C) 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.

Introduction The emergence of drug-resistant cancer cells drastically reduces the efficacy of many antineoplasic agents and, consequently, increases the frequency of therapeutic failure. Benzophenones are known to display many pharmacological properties including cytotoxic activities. The present study was aimed at investigating the cytotoxicity and the modes of action of four naturally occurring benzophenones 2,2′,5,6′-tetrahydroxybenzophenone ( 1 ), isogarcinol ( 2 ), isoxanthochymol ( 3 ) and guttiferone E ( 4 ) on a panel of eleven cancer cell lines including various sensitive and drug-resistant phenotypes. Methods The cytotoxicity of the compounds was determined using a resazurin reduction assay, whereas the caspase-Glo assay was used to detect the activation of caspases 3/7, caspase 8 and caspase 9 in cells treated with compounds 2 – 4 . Flow cytometry was used for cell cycle analysis and detection of apoptotic cells, analysis of mitochondrial membrane potential (MMP) as well as measurement of reactive oxygen species (ROS). Results The four tested benzophenones inhibited the proliferation of all tested cancer cell lines including sensitive and drug-resistant phenotypes. Collateral sensitivity of cancer cells to compounds 1 – 4 was generally better than to doxorubicin. Compound 2 showed the best activity with IC 50 values below or around 1 μM against HCT116 colon carcinoma cells ( p53 +/+) (0.86 μM) and leukemia CCRF–CEM (1.38 μM) cell lines. Compounds 2 – 4 strongly induced apoptosis in CCRF–CEM cells via caspases 3/7, caspase 8 and caspase 9 activation and disruption of MMP. Conclusions The studied benzophenones are cytotoxic compounds that deserve more detailed exploration in the future, to develop novel anticancer drugs against sensitive and otherwise drug-resistant phenotypes.

Betulinic acid (1), 5-hydroxy-3-methoxyxanthone (2), 1,6-dihydroxy-7-methoxyxanthone (3), daucosterol (4), bijaponicaxanthone C (5), hypercalin C (6), 1-hydroxy-6,7-dimethoxyxanthone (7), cadensin D (8) and 5-hydroxy-1,3-dimethoxyxanthone (9) were isolated from the roots of Hypericum riparium. These compounds are reported for the first time from this plant. The extracts and two of the isolated compounds (2 and 8) exhibited both antibacterial and antifungal activities that varied between the microbial species (MIC = 0.97-250 µg/mL). In addition, the brine-shrimp (Artemia salina) lethality bioassay of compound 6 showed potent cytotoxicity with LD 50 of 3.23 µg/mL.

Background Well known as teak, Tectona grandis is widely used in African folk medicine for its pharmacological relevance. In Cameroon, this species is a reputed laxative in the Northern Region while in the Western Region, it is used in the treatment of skin diseases and diarrhoea. Materials and methods Separation and isolation of compounds were performed using different chromatographic methods while their structures were elucidated by spectroscopic techniques including MS and NMR, and by comparison of data with those reported in the literature. Isolated compounds as well as crude ethanol extract were tested for their antibacterial activities using broth micro-dilution method against four Gram negative bacteria strains Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (PA 01), Klebsiella pneumonia (ATCC 11296) and Escherichia aerogenes (ATCC 13048). Results Three known compounds were isolated, including two quinones and one triterpene. They were identified as tectograndone (1), 6-methyl-1,4-dihydroxyanthraquinone (2), and 2β-hydroxyursolic acid (3) respectively. Crude ethanol extract showed good activity against the bacteria strains tested with MIC of 64–256 μg/mL. Among the isolated metabolites, 6-methyl-1,4-dihydroxyanthraquinone exhibited a strong activity against Escherichia aerogenes with MIC of 16 μg/mL, while tectograndone showed a moderate activity against Escherichia coli with MIC of 32 μg/mL. The antibacterial screening of the fruits of this plant as well as that of compounds 1 and 2 is reported herein for the first time. Conclusion The research work presented here shows that Tectona grandis fruits possess compounds which could be developed in the treatment of bacterial diseases.

The present study was designed to investigate the antimicrobial activity and the cytotoxicity of the methanol extract (PLA) as well as fractions (PLA1-4) and compounds [cardamomin (1), (+/-)-polygohomoisoflavanone (2), (S)-(-)-pinostrobin (3), 2',4'-dihydroxy-3',6'-dimethoxychalcone (4), (2S)-(-)-5-hydroxy-6,7-dimethoxyflavanone (5), and (2S)-(-)-5,7-dimethoxyflavanone (6)] obtained from leaves of Polygonum limbatum. The microbroth dilution was used to determine the minimal inhibitory concentration (MIC) of the samples against 11 microbial strains including Candida albicans, C. krusei, C. tropicalis, Aspergillus fumigatus, Pseudomonas aeruginosa, Escherichia coli, vancomycin-resistant Enterococcus faecalis (VRE), Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), S. epidermidis, and Mycobacterium tuberculosis H37Rv. The sulphorhodamine B cell growth inhibition assay was used to assess the cytotoxicity of the above samples on lung A549 adenocarcinoma, breast carcinoma MCF-7, prostate carcinoma PC-3, cervical carcinoma HeLa, and the acute monocytic leukemia cell line THP-1. The results of the MIC determination indicated that, apart from fraction PLA3, all other fractions as well as PLA and compound 3 were selectively active. MIC values were noted on 100% of the 11 tested microorganisms for fraction PLA3, 72.7% for PLA, fraction PLA2, and compound 4, 63.6% for PLA1, and 54.5% for fraction PLA4. The results of the cytotoxicity assay revealed that, except for A459 cells, more than 50% inhibition of the proliferation was obtained with each of the tested samples on at least one of the four other cell lines. IC50 values below 4 mu g/mL were obtained with 1 and 4 on THP-1 cells. The overall results of the present study provided baseline information for the possible use of Polygonum limbatum as well as some of the isolated compounds for the control of cancer diseases and mostly leukemia.

Ethnopharmacological relevance The plant, Vismia rubescens (Guttiferae) is popularly used in Cameroon and in several parts of Africa as febrifugal and for the treatment of various microbial infections (skin diseases, diarrhoea and venereal diseases). Aim of the study This study was mapped out to evaluate the antimicrobial activities of the methanol extract and compounds from the stem bark of Vismia rubescens . Materials and methods Structures of the compounds obtained after column chromatography of the methanol-soluble fraction were determined by spectroscopy and in comparison with published data. The broth micro-dilution method was used to evaluate the antimicrobial activities against three bacteria species ( Salmonella typhi , Stahylococcus aureus and Pseudomonas aeruginosa ) and four yeast species ( Candida albicans , Candida tropicalis , Candida parapsilosis and Cryptococcus neoformans ). Results Chemical analysis of the methanol extract from the stem bark of Vismia rubescens yielded five known compounds 1,4,8-trihydroxyxanthone ( 1 ), 1,7-dihydroxyxanthone ( 2 ), physcion ( 3 ), friedelin ( 4 ) and friedelanol ( 5 ). The crude extract and compounds 1 , 2 and 3 exhibited both antibacterial and antifungal activities that varied between the microbial species (MIC = 3.12–1000 μg/ml). Compounds 2 and 3 were the most active (MIC = 3.12–100 μg/ml) while Stahylococcus aureus and Pseudomonas aeruginosa were sensitive to all the tested compounds. The antimicrobial activity of this plant as well as that of compounds 1 and 2 is being reported here for the first time. Conclusion These results provide promising baseline information for the potential use of this plant as well as some of the isolated compounds in the treatment of skin diseases and diarrhoea.

Stem Bark of Vismia laurentii Michel F. Talaa, Karsten Krohnb, Hidayat Hussainb, Simeon F. Kouamc, Hippolyte K. Waboa, Pierre Tanea, Barbara Schulzd, and Qunxiu Hud a Department of Chemistry, University of Dschang, P.O. Box 67, Dschang, Cameroon b Department of Chemistry, University of Paderborn, Warburger Strase 100, 33098 Paderborn, Germany c Department of Chemistry, Higher Teachers’ Training College, University of Yaounde 1, BP47, Yaounde, Cameroon d Institute of Microbiology, Technical University of Braunschweig, D-38106 Braunschweig, Germany