Antimicrobial activity of selected South African medicinal plants

BACKGROUND

Nearly 3,000 plant species are used as medicines in South Africa, with approximately 350 species forming the most commonly traded and used medicinal plants. In the present study, twelve South African medicinal plants were selected and tested for their antimicrobial activities against eight microbial species belonging to fungi, Mycobacteria, Gram-positive and Gram-negative bacteria.

METHODS

The radiometric respiratory technique using the BACTEC 460 system was used for susceptibility testing against Mycobacterium tuberculosis, and the liquid micro-broth dilution was used for other antimicrobial assays.

RESULTS

The results of the minimal inhibitory concentration (MIC) determinations indicated that the methanol extracts from Acacia karoo, Erythrophleum lasianthum and Salvia africana were able to prevent the growth of all the tested microorganisms. All other samples showed selective activities. MIC values below 100 μg/ml were recorded with A. karoo, C. dentate, E. lasianthum, P. obligun and S. africana on at least one of the nine tested microorganisms. The best activity (MIC value of 39.06 μg/ml) was noted with S. africana against E. coli, S. aureus and M. audouinii, and Knowltonia vesitoria against M. tuberculosis.

CONCLUSION

The overall results of the present work provide baseline information for the possible use of the studied South African plant extracts in the treatment of microbial infections.

Cytotoxicity and antimicrobial activity of the methanol extract and compounds from Polygonum limbatum

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 µg/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.

Antibacterial activity and cytotoxicity of selected Egyptian medicinal plants

Medicinal plants have been used as a source of remedies since ancient times in Egypt. The present study was designed to investigate the antibacterial activity and the cytotoxicity of the organic extracts from 16 selected medicinal plants of Egypt. The study was also extended to the isolation of the antiproliferative compound jaeschkeanadiol p-hydroxybenzoate (FH-25) from Ferula hermonis. The microbroth dilution was used to determine the minimal inhibitory concentration (MIC) of the samples against twelve bacterial strains belonging to four species, Providencia stuartii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli, while a resazurin assay was used to assess the cytotoxicity of the extracts on the human pancreatic cancer cell line MiaPaCa-2, breast cancer cell line MCF-7, CCRF-CEM leukemia cells, and their multidrug resistant subline, CEM/ADR5000. The results of the MIC determination indicated that all the studied crude extracts were able to inhibit the growth of at least one of the tested bacterial species, the best activity being recorded with the crude extracts from F. hermonis and Vitis vinifera, whichwere active against 91.7% and 83.3% of the studied bacteria, respectively. The lowest MIC value of 128 μg/mL was recorded against P. stuartii ATCC 29916 and E. coli ATCC 10536 with the extract from V. vinifera and Commiphora molmol, respectively. In the cytotoxicity study, IC50 values below 20 μg/mL were recorded for the crude extract of F. hermonis on all four studied cancer cell lines. FH-25 also showed good cytotoxicity against MCF-7 cells (IC50: 2.47 μg/mL). Finally, the results of the present investigation provided supportive data for the possible use of the plant extracts investigated herein, mostly F. hermonis and V. vinifera in the treatment of bacterial infections and jaeschkeanadiol p-hydroxybenzoate in the control of cancer diseases.

Cytotoxicity and mode of action of four naturally occuring flavonoids from the genus Dorstenia: gancaonin Q, 4-hydroxylonchocarpin, 6-prenylapigenin, and 6,8-diprenyleriodictyol

Several flavonoid-like compounds were found to possess good antiproliferative properties. Herein, we examined the ability of four naturally occuring and biologically active flavonoids from the genus Dorstenia, gancaonin Q (1), 6-prenylapigenin (2), 6,8-diprenyleriodictyol (3), and 4-hydroxylonchocarpin ( 4), to inhibit the proliferation of a panel of fourteen cancer cell lines including leukemia and solid cancer cells, as well as AML12 normal hepatocytes. The study was extended to the analysis of cell cycle distribution, apoptosis induction, and caspase 3/7 activity and the antiangiogenic properties of the four compounds. The results of the cytotoxicity assays showed that more than 50 % inhibition of proliferation was obtained with compound 1 on all the fourteen studied cancer cell lines, with IC (50) values below 20 µg/mL. Compounds 2, 4, and 3 showed selective activity, with IC (50) values below 20 µg/mL being noted on 57.15 %, 71.42 %, and 85.71 % of the fourteen cancer cell lines, respectively. None of the compounds exhibited more than 50 % inhibition against AML12 normal hepatocytes cells at 20 µg/mL. IC (50) values below or around 4 µg/mL were recorded on 28.57 % of the tested cell lines for both compound 1 and 4 and 21.43 % for compound 3, which appeared to be the best cytotoxic compounds. This study indicates that caspase 3/7 activation is one of the modes of induction of apoptosis for compounds 1, 3, and 4 in CCRF-CEM cells. The results of the antiangiogenic assay indicated that compounds 1, 3, and 4 were also able to inhibit the growth of blood capillaries on the chorioallantoic membrane of quail eggs, the best effect being noted for compound 4 (54.1 % inhibition). The results of the present work provide evidence of the cytotoxic potential of the four studied flavonoids and supportive data for further investigations.

A new fatty aldol ester from the aerial part of Mimosa invisa (Mimosaceae)

A new aldol ester named 17-O-triacontanoylheptadecanal (1) was isolated from the aerial part of Mimosa invisa (Mimosaceae) together with eight known compounds identified as β-sitosterol (2), α-amyrine (3), lupeol (4), 4'-O-methylepinumisoflavone (5), alpinumisoflavone (6), betulinic acid (7), 3-O-β-D-glucopyranoside of sitosterol (8) and epirobinetinidol (9). The structures of compounds were determined on the basis of NMR and mass spectrometry data as well as by comparing the data reported in the literatures. The antimicrobial activities of the crude extract and compounds 1 and 9 were investigated against seven microbial species. The natural products showed moderate activities compared to that of the crude extract.

Antibacterial activities of selected Cameroonian spices and their synergistic effects with antibiotics against multidrug-resistant phenotypes

Background

The emergence of multi-drug resistant (MDR) phenotypes is a major public health problem today in the treatment of bacterial infections. The present study was designed to evaluate the antibacterial activities of the methanol extracts of eleven Cameroonian spices on a panel of twenty nine Gram negative bacteria including MDR strains.

Methods

The phytochemical analysis of the extracts was carried out by standard tests meanwhile the liquid micro-broth dilution was used for all antimicrobial assays.

Results

Phytochemical analysis showed the presence of alkaloids, phenols and tannins in all plants extracts. The results of the antibacterial assays indicated that all tested extracts exert antibacterial activities, with the minimum inhibitory concentration (MIC) values varying from 32 to 1024 μg/ml. The extracts from Dichrostachys glomerata, Beilschmiedia cinnamomea, Aframomum citratum, Piper capense, Echinops giganteus, Fagara xanthoxyloïdes and Olax subscorpioïdea were the most active. In the presence of efflux pump inhibitor, PAßN, the activity of the extract from D. glomerata significantly increased on 69.2% of the tested MDR bacteria. At MIC/5, synergistic effects were noted with the extract of D. glomerata on 75% of the tested bacteria for chloramphenicol (CHL), tetracycline (TET) and norfloxacin (NOR). With B. cinnamomea synergy were observed on 62.5% of the studied MDR bacteria with CHL, cefepime (FEP), NOR and ciprofloxacin (CIP) and 75% with erythromycin (ERY).

Conclusion

The overall results provide information for the possible use of the studied extracts of the spices in the control of bacterial infections involving MDR phenotypes.

Pharmacogenomics of Cameroonian traditional herbal medicine for cancer therapy

ETHNOPHARMACOLOGICAL RELEVANCE

A socio-economic burden associated with cancers is reported in Africa. Ethnopharmacological usages such as immune and skin disorders, inflammatory, and others chould be considered when selecting plants used to treat cancer, since these reflect disease states bearing relevance to cancer or a cancer symptoms.

MATERIALS AND METHODS

Documented compounds of Cameroonian medicinal plants were used as keywords in the National Cancer Institute (NCI) database to establish a library of cytotoxic compounds. Cellular and pharmacogenomic profiling was then performed for the 10 most cytotoxic natural products. By COMPARE and hierarchical cluster analyses, candidate genes were identified whose mRNA expression significantly predicted sensitivity or resistance of cell lines to the two most cytotoxic compounds.

RESULTS

Up to 974 compounds isolated from 148 medicinal plants were used as keywords in the NCI database to establish a library of 27 cytotoxic compounds. Two of the 10 most cytotoxic compounds, plumericin from Plumeria rubra and plumbagin from Diospyros crassiflora and Diospyros canaliculata, were analyzed in more detail. The IC(50) values for plumericin and plumbagin of 60 NCI cell lines were associated with the microarray-based transcriptome-wide mRNA expression. Genes products identified for plumericin activity are mainly involved in enzymatic activity, transcriptional processes or are structural constituents of ribosomes. Products identified for plumbagin activity are involved in several processes, but they are mostly the strucrural constituents of ribosomes or involved in enzymatic activity.

CONCLUSIONS

The most significant progress of the present investigation, the first of its kind ever reported for investigated natural product in Sub-Saharan Africa, was the connection between traditionally used medicinal plants and the mechanistic analysis, such as pharmacogenomics.

Evaluation of four Cameroonian medicinal plants for anticancer, antigonorrheal and antireverse transcriptase activities

Methanol extracts from the leaves, bark and roots of four Cameroonian medicinal plants, Bersama engleriana, Cupressus lusitanica, Vitellaria paradoxa and Guibourtia tessmannii were tested for their in vitro cytotoxicity, antigonorrheal and antireverse transcriptase activities. The XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt) assay, the dilution method and reverse transcriptase (RT) assay were used for the investigations. Preliminary phytochemical analysis of the extracts was also conducted using standard methods. Results showed that all extracts contained compounds belonging to the classes of phenols and terpenoids. They were also able to reduce in dose dependent manner, the proliferation of the cancer THP-1, DU145, HeLa, MCF-7, HepG2 and the normal Vero cells. IC(50) values below 30μg/ml were noted with extract from the three parts of B. engleriana on at least two of the five studied cancer cell lines, the lowest value of 5.9μg/ml being obtained with sample from the bark. IC(50) values below 30μg/ml were also recorded with extracts from the leaves (on HeLa cells) and bark (on MCF-7) of G. tessmanii, and that from the bark of C. lusitanica on MCF-7. Extracts from B. engleriana and those from the bark of V. paradoxa gave the minimal inhibitory concentrations (MIC) values below 100μg/ml on most of the 10 tested Nesseria gonorrhoeae strains. Extracts from B. engleriana also inhibited more than 80% the activity of the Human Immuno-deficiency Virus (HIV) enzyme. Finally, the results of the present study provide baseline information for the use of B. engleriana, C. lusitanica, G. tessmanii, V. paradoxa.

Anticancer activities of six selected natural compounds of some Cameroonian medicinal plants

BACKGROUND

Natural products are well recognized as sources of drugs in several human ailments. In the present work, we carried out a preliminary screening of six natural compounds, xanthone V(1) (1); 2-acetylfuro-1,4-naphthoquinone (2); physcion (3); bisvismiaquinone (4); vismiaquinone (5); 1,8-dihydroxy-3-geranyloxy-6-methylanthraquinone (6) against MiaPaCa-2 pancreatic and CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000. Compounds 1 and 2 were then tested in several other cancer cells and their possible mode of action were investigated.

METHODOLOGY/FINDINGS

The tested compounds were previously isolated from the Cameroonian medicinal plants Vismia laurentii (1, 3, 4, 5 and 6) and Newbouldia laevis (2). The preliminary cytotoxicity results allowed the selection of xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, which were then tested on a panel of cancer cell lines. The study was also extended to the analysis of cell cycle distribution, apoptosis induction, caspase 3/7 activation and the anti-angiogenic properties of xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone. IC(50) values around or below 4 µg/ml were obtained on 64.29% and 78.57% of the tested cancer cell lines for xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, respectively. The most sensitive cell lines (IC(50)<1 µg/ml) were breast MCF-7 (to xanthone V(1)), cervix HeLa and Caski (to xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone), leukemia PF-382 and melanoma colo-38 (to 2-acetylfuro-1,4-naphthoquinone). The two compounds showed respectively, 65.8% and 59.6% inhibition of the growth of blood capillaries on the chorioallantoic membrane of quail eggs in the anti-angiogenic assay. Upon treatment with two fold IC(50) and after 72 h, the two compounds induced cell cycle arrest in S-phase, and also significant apoptosis in CCRF-CEM leukemia cells. Caspase 3/7 was activated by xanthone V(1).

CONCLUSIONS/SIGNIFICANCE

The overall results of the present study provided evidence for the cytotoxicity of compounds xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, and bring supportive data for future investigations that will lead to their use in cancer therapy.

Antimicrobial activities of the methanol extract and compounds from Artocarpus communis (Moraceae)

Background

Artocarpus communis is used traditionally in Cameroon to treat several ailments, including infectious and associated diseases. This work was therefore designed to investigate the antimicrobial activities of the methanol extract (ACB) and compounds isolated from the bark of this plant, namely peruvianursenyl acetate C (1), α-amyrenol or viminalol (2), artonin E (4) and 2-[(3,5-dihydroxy)-(Z)-4-(3-methylbut-1-enyl)phenyl]benzofuran-6-ol (5).

Methods

The liquid microdilution assay was used in the determination of the minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC), against seven bacterial and one fungal species.

Results

The MIC results indicated that ACB as well as compounds 4 and 5 were able to prevent the growth of all tested microbial species. All other compounds showed selective activities. The lowest MIC value of 64 μg/ml for the crude extract was recorded on Staphylococcus aureus ATCC 25922 and Escherichia coli ATCC 8739. The corresponding value of 32 μg/ml was recorded with compounds 4 and 5 on Pseudomonas aeruginosa PA01 and compound 5 on E. coli ATCC 8739, their inhibition effect on P. aeruginosa PA01 being more than that of chloramphenicol used as reference antibiotic.

Conclusion

The overall results of this study provided supportive data for the use of A. communis as well as some of its constituents for the treatment of infections associated with the studied microorganisms.

Cytotoxicity of some Cameroonian spices and selected medicinal plant extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Several medicinal plants and spices are used traditionally to treat cancers in Cameroon.

AIM

Methanol extracts from thirty-four spices and plants, with related ethnobotanical use were investigated for their in vitro cytotoxicity on the human pancreatic cancer cell line MiaPaCa-2, leukemia CCRF-CEM cells and their multidrug resistant (MDR) subline CEM/ADR5000, and the normal human umbilical vein endothelial cells (HUVECs). In addition the anti-angiogenic properties of the most active extracts were investigated.

MATERIAL AND METHODS

The MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay was used for cytotoxic studies and the CAM-assay (chicken-chorioallantoic-membrane-assay) for anti-angiogenesis test.

RESULTS

The results of the cytotoxicity tests indicated that, when tested at 20 μg/ml, extracts from Xylopia aethiopica, Echinops giganteus, Imperata cylindrica, Dorstenia psilirus and Piper capense were able to inhibit more that 50% the proliferation of the three tested cancer cells (MiaPaCa-2, CEM/ADR5000 CCRF-CEM). The lowest IC(50) values of 6.86 μg/ml on MiaPaCa-2 and 3.91 μg/ml on CCRF-CEM cells were obtained with X. aethiopica, while the corresponding value of 6.56 μg/ml was obtained with P. capense on CEM/ADR5000 cells. Against leukemia cells, no cross-resistance was observed with I. cylindrica, P. capense and Zinziber officinalis. Extracts from D. psilirus and E. giganteus were able to inhibit angiogenesis by more than 50% in quail embryo.

CONCLUSION

The overall results of the present study provide supportive data on the use of some Cameroonian plants for cancer treatment.

Antimicrobial activities of the methanol extract, fractions and compounds from Ficus polita Vahl. (Moraceae)

BACKGROUND

Many plants of the family Moraceae are used in the treatment of infectious diseases. Ficus polita Vahl., an edible plant belonging to this family is used traditionally in case of dyspepsia, infectious diseases, abdominal pains and diarrhea. The present work was designed to assess the antimicrobial activity of the methanol extract from the roots of F. polita (FPR), as well as that of its fractions (FPR1-5) and two of the eight isolated compounds, namely euphol-3-O-cinnamate (1) and (E)-3,5,4'-trihydroxy-stilbene-3,5-O-β-D-diglucopyranoside (8).

METHODS

The liquid microdilution assay was used in the determination of the minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC), against seven bacterial and one fungal species.

RESULTS

The results of the MIC determination showed that the crude extract, fractions FPR1, FPR2 and compound 8 were able to prevent the growth of the eight tested microorganisms. Other samples showed selective activity. The lowest MIC value of 64 μg/ml for the crude extract was recorded on 50% of the studied microbial species. The corresponding value for fractions of 32 μg/ml was obtained on Salmonella typhi, Escherichia coli and Candida albicans ATCC strains. The MIC values recorded with compound 8 on the resistant Pseudomonas aeruginosa PA01 strain was equal to that of chloramphenicol used as reference antibiotic.

CONCLUSION

The obtained results highlighted the interesting antimicrobial potency of F. polita as well as that of compound 8, and provided scientific basis for the traditional use of this taxon in the treatment of microbial infections.

Antioxidant, antitumor and antimicrobial activities of the crude extract and compounds of the root bark of Allanblackia floribunda

CONTEXT

 Allanblackia floribunda Oliver (Guttiferae) is an African medicinal plant used traditionally to treat a variety of ailments.

OBJECTIVE

 We investigated the antitumor, radical scavenging, antimycobacterial, antibacterial and antifungal activities of the root bark extract of A. floribunda and three isolated phenolics, namely 1,7-dihydroxyxanthone (1), morelloflavone (2) and 7'-O-glucoside of morelloflavone (3).

MATERIALS AND METHODS

 The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging assay was used for antioxidant tests, while crown gall tumor assay was used for assay of antitumor activity. The p-iodonitrotetrazolium chloride (INT) colorimetry and Microplate Alamar Blue Assay (MABA) were used for antimicrobial investigations.

RESULTS

 Moderate tumor reducing activity was observed with the extract, while better activities were recorded with compounds 2 and 3. The antimycobacterial and antitumor activities of the extract are being reported for the first time. The DPPH radical scavenging test showed that all the studied samples were able to scavenge more than 50% of the free radical, with compound 3 showing the best inhibitory activity (IC(50) of 49.08 µg/mL). Compounds 1 to 3 prevented the growth of Mycobacterium smegmatis and both extract and compound 2 were active on M. tuberculosis. The lowest MIC value for the extract (9.76 μg/mL) was recorded against Enterobacter aerogenes while the corresponding value for the compounds (4.88 µg/mL) was obtained with compound 2 on Trichophyton rubrum.

DISCUSSION AND CONCLUSION

 The overall results of the present work provide baseline information for the potential use of the root bark extract of A. floribunda as an antimicrobial, antitumor and antioxidant phytomedicine.

Cameroonian medicinal plants: pharmacology and derived natural products

Many developing countries including Cameroon have mortality patterns that reflect high levels of infectious diseases and the risk of death during pregnancy and childbirth, in addition to cancers, cardiovascular diseases and chronic respiratory diseases that account for most deaths in the developed world. Several medicinal plants are used traditionally for their treatment. In this review, plants used in Cameroonian traditional medicine with evidence for the activities of their crude extracts and/or derived products have been discussed. A considerable number of plant extracts and isolated compounds possess significant antimicrobial, anti-parasitic including antimalarial, anti-proliferative, anti-inflammatory, anti-diabetes, and antioxidant effects. Most of the biologically active compounds belong to terpenoids, phenolics, and alkaloids. Terpenoids from Cameroonian plants showed best activities as anti-parasitic, but rather poor antimicrobial effects. The best antimicrobial, anti-proliferative, and antioxidant compounds were phenolics. In conclusion, many medicinal plants traditionally used in Cameroon to treat various ailments displayed good activities in vitro. This explains the endeavor of Cameroonian research institutes in drug discovery from indigenous medicinal plants. However, much work is still to be done to standardize methodologies and to study the mechanisms of action of isolated natural products.

Evaluation of flavonoids from Dorstenia barteri for their antimycobacterial, antigonorrheal and anti-reverse transcriptase activities

The aim of this study was to evaluate the antimycobacterial, antigonorrheal and reverse transcriptase activities of five flavonoids: isobachalcone (IBC); kanzanol C (KAN); 4-hydroxylonchocarpin (4-LCP); stipulin (SPL) and amentoflavone (AMF) from Dortenia barteri, together with the crude extract from this plant. The Agar disc diffusion, broth microdilution, microplate alamar blue assay (MABA), radiometric respiratory technique using BACTEC 460 system and the reverse transcriptase (RT) assay were used for the investigations. The results of the antimycobacterial assay showed that the crude extract and compounds were able to prevent the growth of Mycobacteria with MIC<10 microg/ml being recorded with IBC on M. tuberculosis. Results of the killing rate experiment revealed that total inhibition effect on M. tuberculosis H37Rv strain was noted with IBC and SPL at day 9 when tested at 4x MIC. The results of the antigonorrheal assay indicated that MIC values below 10 microg/ml were also recorded with IBC on all the tested N. gonorrhoeae strains, meanwhile good activities (MIC<10 microg/ml) were also noted with the extract, KAN, 4-LCP and SPL on some of these strains. The anti-reverse transcriptase activities of extract and compounds also demonstrated that all samples were able to inhibit at various extents the reverse transcriptase activity, with IBC and 4-LCP showing the best effects. The overall results of this work provided evidence that the crude extract as well as some flavonoids from D. barteri could be potential sources of new antimicrobial drug against tuberculosis (TB), gonorrhea and probably the acquired immunodeficiency syndrome.

Potential of Cameroonian plants and derived products against microbial infections: a review

In Cameroon, infectious diseases are amongst the most commonly notified diseases and largest cause of mortality. Many plants are used locally in traditional medicine for their treatment. The aim of the present review is to summarize currently available evidence and knowledge concerning Cameroonian plants used to treat bacterial and fungal infections, and the efficacy of plant-derived extracts and compounds. The traditional uses of plants in the treatment of infectious diseases have been collected and tabulated. The antimicrobial activity of the extracts and the chemical constituents of most of these plants are summarized in this report. Plants used traditionally in Cameroonian medicine, with laboratory work on any part or products, have been documented. Numerous extracts and compounds have been tested for antimycobacterial, antibacterial and antifungal efficacy and some of them were significantly active. Most of the bioactive compounds isolated were phenolics and alkaloids. In conclusion, many plant species are used in traditional medicine in Cameroon to treat infectious diseases, and several interesting openings have originated for further inquiry following IN VITRO antimicrobial activity evaluation. However, much work is still to be done to standardize methods and cut-off points for describing the antimicrobial activity, and on the study of the mechanisms of action.

Synthesis of some p-toluenesulfonyl-hydrazinothiazoles and hydrazino-bis-thiazoles and their anticancer activity

A series of novel p-toluenesulfonyl-hydrazinothiazoles and hydrazino-bis-thiazoles derivatives (2a-f, 3a-f and 5-8) were synthesized by initial condensation of p-toluenesulfonylthiosemicarbazide 1 with a series of α-halogenocarbonyls in acetone or dimethylformamide (DMF)/acetone, mixture. All our synthesized compounds were submitted for further acylation reaction in the presence of acetic anhydride. The structures of newly synthesized derivatives 2a-f, 3a-f and 5-8 were confirmed by IR, (1)H-NMR, EIMS spectral data and elemental analysis. Compounds 2a, 2c, 2d, 2e and 3a showed significant anticancer activities (IC(50)<10 μM) on both prostate DU-145 and hepatocarcinoma Hep-G2 cancer cell lines.

Toxicological evaluation of the hydroethanol extract of Tabernaemontana crassa (Apocynaceae) stem bark

AIM

Tabernaemontana crassa Benth. is a medicinal plant widely used in Cameroon folk medicine to treat a variety of affections. This study was aimed at evaluating its toxicological profile.

MATERIALS AND METHODS

The 70% (v/v) hydroethanol (HE) extract from the stem bark of this plant was given to albino Wistar rats by oral gavage to study the acute and sub-acute toxicities.

RESULTS

The results of histopathological studies revealed that there was a dose-related effect in liver, lungs and kidneys and that there was no difference in tissue profile of control group and those receiving 6 weeks daily treatment of 0.5 g/kg b.w. The result of the acute toxicity indicated the medium lethal dose (LD50) of 6.75 g/kg body weight (b.w.) after 48 h of treatment and the significant variation (P<0.05) of the relative body weight, serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), total bilirubin (TBil), direct bilirubin (DBil) and creatinine (SCr) at the dose of 6g/kg b.w. These results also indicated significant variation of the liver alkaline phosphatase, aspartate aminotransferase (AST), ALT, total proteins (TP), glutathione (GSH) and malondialdehyde (MDA) and renal creatinine (RCr) and urea (RU) at 6g/kg b.w. The result of the sub-acute toxicity showed significant changes in the body weight but no modification (P>0.05) of blood and liver indices for the animal taking 6 weeks daily doses of the HE compared to the control group.

CONCLUSIONS

The results showed that this extract was fairly non-toxic but that consumption of higher doses up to 6 g/kg b.w. could cause organ injuries. Moderated consumption of small doses up to 0.5 g/kg b.w. daily for 6 weeks appeared to be safe.

Pycnanthulignenes A-D, antimicrobial cyclolignene derivatives from the roots of Pycnanthus angolensis

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.

Two new antimicrobial dimeric compounds: febrifuquinone, a vismione-anthraquinone coupled pigment and adamabianthrone, from two Psorospermum species

Febrifuquinone (1), a new vismione-anthraquinone coupled pigment and a new bianthrone named adamabianthrone (2), were isolated respectively, from the roots of Psorospermum febrifugum and from the bark of Psorospermum adamauense along with eight known compounds including: two bianthrones [(bianthrone A(1) (3) and bianthrone A(2b)], one vismione [(vismione D (4)], one anthrone (3-geranyloxyemodin anthrone) and four anthraquinones [(1,8-dihydroxy-3-isoprenyloxy-6-methylanthraquinone, emodin (5), 3-geranyloxy-1,8-dihydroxy-6-methylanthraquinone and 2-geranyl-1,8-dihydroxy-6-methylanthraquinone]. Their structures were determined using modern spectroscopic methods including one and two dimensional-NMR techniques as well as MS. Compounds 1 and 2 showed significant antimicrobial activities against a wide range of bacteria and fungi.

Antimicrobial activity of the methanolic extract and compounds from Morus mesozygia stem bark

AIM OF THE STUDY

This study was aimed at investigating the antimicrobial activity of the methanolic extract (MMB) and compounds isolated from the stem bark of Morus mesozygia, namely 3beta-acetoxyurs-12-en-11-one (1), moracin Q (2), moracin T (3), artocarpesin (4), cycloartocarpesin (5), moracin R (6), moracin U (8), moracin C (9), and moracin M (10).

MATERIALS AND METHODS

The liquid microdilution assay was used in the determination of the minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC), against nine bacterial and two fungal species.

RESULTS

The results of the MIC determination showed that the compounds 3, 4, 8 and 9 were able to prevent the growth of all tested microbial species. All other samples showed selective activities. Their inhibitory effects were noted on 90.9% studied organisms for the crude extract, 81.8% for compound 6, 72.7% for compound 10, 63.6% for compound 1, 54.5% for compound 5, and 45.5% for compound 2. The lowest MIC value of 39 microg/ml was obtained with the crude extract against Escherichia coli. The corresponding value for compounds (5 microg/ml) was registered with compound 9 on Shigella dysenteriae and compound 3 on E. coli, S. dysenteriae, Pseudomonas aeruginosa, Salmonella typhi and Bacillus cereus. The lowest MIC value (39 microg/ml) observed with the crude extract (on E. coli) was only eightfold greater than that of gentamycin used as reference antibiotic (RA) while the corresponding value (5 microg/ml) recorded with compounds 3 and 9 was equal to that of RA on the corresponding microorganisms.

CONCLUSIONS

The obtained results highlighted the interesting antimicrobial potency of M. mesozygia as well as that of the studied compounds, and provided scientific basis for the traditional use of this species.

Antimicrobial activity of the crude extract, fractions and compounds from stem bark of Ficus ovata (Moraceae)

AIM OF THE STUDY

This study was designed to investigate the antimicrobial activities of the methanol extracts from the stem bark of Ficus ovata (FOB), fractions (FOB1-6) and compounds isolated following bio-guided fractionation [3-friedelanone (1), taraxeryl acetate (2), betulinic acid (3), oleanoïc acid (4), 2-hydroxyisoprunetin (5), 6,7-(2-isopropenyl furo)-5,2,4-trihydroxyisoflavone (6), Cajanin (7) and protocatechuic acid (8)].

MATERIALS AND METHODS

The micro-dilution method was used for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) against fungi (two species), gram-positive (three species) and gram-negative bacteria (five species).

RESULTS

The results of the MIC determinations indicated that the crude extract (FOB), fractions FOB2 and FOB4 as well as compound 5 were active on the entire studied organisms. Other samples showed selective activity, fractions FOB1, FOB3 and FOB5 being active against 50% of the tested microbial species while FOB6 was active on 40%. Compounds 8, 6, 2 and 7 prevented the growth of 80%, 70%, 50% and 20% of the organisms respectively. The lowest MIC value (156 g/ml) observed with the crude extract was recorded on Streptococcus faecalis, Candida albicans and Microsporum audouinii. The corresponding value for fractions (39 microg/ml) was noted with FOB4 against Staphylococcus aureus, while that of the tested compounds (10 microg/ml) was observed with compound 8 on Microsporum audouinii. The results of the MMC determination suggested that the cidal effect of most of the tested samples on the studied microorganisms could be expected.

CONCLUSIONS

The overall results provided evidence that the studied plant extract, as well as some of the isolated compounds might be potential sources of new antimicrobial drug.

Coumestan Glycosides from the Stem Bark of Cylicodiscus Gabunensis

Two new coumestan glycosides, coumestoside C (1) and coumestoside D (2), were isolated from the stem bark of Cylicodiscus gabunensis Harms. Their structures were established by spectroscopic means and chemical transformations as 9- O-α-L-rhamnopyranosyl-3-hydroxy-4-(5′-hydroxy-3′-methylbut-2′ E-enyl) coumestan (1) and 9- O-β-D-galactopyranosyl-3- O- prenyl-4-hydroxycoumestan. Coumestoside C exhibited antimicrobial activity against Proteus vulgaris.

Coumestan glycosides from the stem bark of Cylicodiscus gabunensis

Two new coumestan glycosides, coumestoside C (1) and coumestoside D (2), were isolated from the stem bark of Cylicodiscus gabunensis Harms. Their structures were established by spectroscopic means and chemical transformations as 9-O-alpha-L-rhamnopyranosyl-3-hydroxy-4-(5'-hydroxy-3'-methylbut-2'E-enyl) coumestan (1) and 9-O-beta-D-galactopyranosyl-3-O- prenyl-4-hydroxycoumestan. Coumestoside C exhibited antimicrobial activity against Proteus vulgaris.

Flavanones from the Stem Bark of Erythrina Sigmoidea

Chemical analysis of the stem bark of Erythrina sigmoidea Hua yielded two new flavonoids, designated sigmoidin M (1) and sigmoidin N (2). Their structures were established by chemical and spectroscopic means as 5,7-dihydroxy-3′-O-prenyl-(3″,4″-dihydroxy-2″,2″-dimethylpyrano)[5″,6″:4′,5']flavanone (1) and 5,7,3′-trihydroxy-(3″-hydroxy-2″-(1-hydroxyisopropyl)-[4′,5:4″,5″]furanoflavanone (2), respectively. Sigmoidin M exhibited antimicrobial activity.

Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae)

The aim of this study was to evaluate the antimicrobial activity of the methanol extracts from Ficus chlamydocarpa (FCR), Ficus cordata (FCB), mixture of the two plants (FCM), as well as that of the isolated flavonoids Alpinumisoflavone (2), Genistein (3), Laburnetin (4), Luteolin (5) (isolated from FCR), Catechin (7) and Epiafzelechin (8) (isolated from FCB). Mycobacteria, fungi, Gram-positive and Gram-negative bacterial species were tested for their susceptibility to the above samples. The microplate dilution and radiometric respiratory methods were used to determine the susceptibility testing of the samples against Mycobacterium smegmatis and Mycobacterium tuberculosis, respectively. The disc diffusion assay was used to determine the sensitivity of the samples, whilst the micro-dilution method was used for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) against fungi, Gram-positive and Gram-negative bacterial species. All the samples except compound 7 were found to be active to Mycobacterium smegmatis and the MIC ranged from 0.61 to 312.50microg/ml. Compound 4 showed the best activity against Mycobacterium tuberculosis exhibiting an MIC of 4.88microg/ml. The results of the diffusion test indicated that the crude extract from FCB, FCM as well as compounds 5 and 8 were able to prevent the growth of all tested (fungi, Gram-positive and Gram-negative bacteria) organisms. The inhibition effect of the crude extract from Ficus chlamydocarpa was observed on 10 (62.5%) of the 16 tested microorganisms (excluding mycobacteria) whereas that of compounds 4, 2 and 3 was respectively noted on 14 (87.5%), 8 (50.0%) and 7 (39.9%) of the tested microbial species. FCB was found to be more active than FCR on most of the tested organisms. The results provided evidence that the studied plants extract, as well as some of the isolated compounds might be potential sources of new antimicrobial drug.

Semisynthesis and antitumoral activity of 2-acetylfuranonaphthoquinone and other naphthoquinone derivatives from lapachol

Ozonolysis of lapachol (1), resulting in an unusual formation of a potent antitumor agent 2-acetylfuranonaphthoquinone (3) along with the expected aldehyde 6, is described. The reaction of lapachol (1) with CAN in dry acetonitrile leading to biologically active furanonaphthoquinones is also reported. The antitumoral activity of the tested compounds on human DU-145 prostate carcinoma cells was evaluated following XTT assay. The results revealed that 2-(1-methylethenyl)-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (5), beta-lapachone (10) and dehydro-beta-lapachone diacetate (11) showed 100% inhibition at 25 microg/ml. All the tested samples showed dose-dependent activity.

Antimicrobial activity of the crude extracts and five flavonoids from the twigs of Dorstenia barteri (Moraceae)

The aim of this study was to evaluate the antimicrobial activity of the crude extract of the twigs of Dorstenia barteri (DBT) as well as that of four of the five flavonoids isolated from this extract. Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and fungi (four species) were used. The agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that DBT, isobavachalcone (1), and kanzonol C (4) prevented the growth of all the 22 tested microbial species. Other compounds showed selective activity. The inhibitory activity of the most active compounds namely compounds 1 and 4 was noted on 86.4% of the tested microorganisms and that of 4-hydroxylonchocarpin (3) was observed on 72.7%. This lowest MIC value of 19.06microg/ml was observed with the crude extract on seven microorganisms namely Citrobacter freundii, Enterobacter aerogens, Proteus mirabilis, Proteus vulgaris, Bacillus megaterium, Bacillus stearothermophilus and Candida albicans. For the tested compounds, the lowest MIC value of 0.3microg/ml (on six of the 22 organisms tested) was obtained only with compound 1, which appeared as the most active compound. This lowest MIC value (0.3microg/ml) is about 4-fold lower than that of the RA, indicating the powerful and very interesting antimicrobial potential of isobavachalcone (1). The antimicrobial activities of DBT, as well as that of compounds 1, 3, 4, amentoflavone (5) are being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extracts from DBT as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Antimicrobial activity of the methanolic extract, fractions and compounds from the stem bark of Irvingia gabonensis (Ixonanthaceae)

The antimicrobial activity of the methanolic extract from the stem bark of Irvingia gabonensis (IGM), fractions and compounds isolated from IGM [3-friedelanone (1), betulinic acid (2), oleanolic acid (3), 3,3',4'-tri-O-methylellagic acid (4), 3,4-di-O-methylellagic acid (5) and hardwickiic acid (6)] was evaluated against Gram-positive bacteria (6 species), Gram-negative bacteria (13 species) and three Candida species using dilution methods for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC). From the obtained results, IGM prevented the growth of all the species of microorganisms tested at a concentration limit of 312.50 microg/ml. Compounds 4-6 also inhibited the growth of all the tested microbial species while compounds 1-3 showed selective activities. The lowest MIC values (78.12 microg/ml) were obtained with IGM on 13 of the 22 microorganisms tested. The corresponding value of 1.22 microg/ml (4.26 microM) for compounds was recorded with compound 6 on Neisseria gonorrhoeae. The obtained results confirmed the use of Irvingia gabonensis in the treatment of bacterial and fungal infections.

Antimicrobial activity of the methanolic extracts and compounds from Treculia obovoidea (Moraceae)

The crude extract from Treculia obovoidea was subjected to purification by repeated chromatography. Eight compounds were isolated from Treculia obovoidea and identified as Psoralen (1), Bergapten (2), 7-methoxycoumarin (3), 7-hydroxycoumarin (4), 4,2',4'-trihydroxychalcone (5), 4,2',4'-trihydroxy-3-prenylchalcone (6), 3-hydroxy-4-methoxybenzoic acid (7) and O-[3-(2,2-dimethyl-3-oxo-2H-furan-5-yl) butyl] bergaptol (8). These compounds together with the extract were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and three Candida species using micro-dilution methods for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC). The MIC values obtained with the crude extracts varied from 78.12 to 156.25 microg/ml against 17 (80.95%) of the 21 tested microorganisms. All the isolated compounds showed selective activity. The antimicrobial activity of this plant as well as that of compounds 6 and 8 is being reported for the first time. The obtained results provide promising baseline information for the potential use of these crude extract as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Antimicrobial activity of the methanolic extract and of the chemical constituents isolated from Newbouldia laevis

The methanolic extract (NLB) and ten compounds isolated from the root bark of Newbouldia laevis Seem, namely chrysoeriol (1), newbouldiaquinone (2), 2-acetylfuro-1,4-naphthoquinone (3), 2-hydroxy-3-methoxy-9,10-dioxo-9,10-dihydroanthracene-1-carbaldehyde (4), lapachol (5), beta-sitosterol-3-O-beta-D-glucopyranoside (6), oleanolic acid (7), canthic acid (8) newbouldiamide (9) and 2-(4-hydroxyphenyl)-ethyltrioctanoate (10), were tested for in vitro antimicrobial activity. Twenty one microorganisms belonging to six Gram-positive and twelve Gram-negative bacterial species as well as three yeasts from Candida species were tested for their susceptibility to NLB and the pure isolated compounds based on the Agar Hole Diffusion test and the Liquid Dilution method. The Hole Diffusion assay indicated that NLB and compound 7 were active against all tested pathogens while other compounds showed selective activity with the antimicrobial spectra varying from 76% (compound 10) to 95 % (compound 6). Minimal inhibitory concentrations (MIC) also illustrated the important antimicrobial activity of NLB and of the isolated compounds. MIC values obtained varied from 9.76 to 312.50 microg/ml for NLB, and 0.038 to 9.76 microg/ml for pure compounds against most of the tested microorganisms. The antimicrobial activities of compounds 2, 4 and 9 are described here extensively for the first time. The results indicate a promising basis for the use of Newbouldia laevis and some of its active principles in the treatment of infectious diseases.

Antimicrobial activity of the methanolic extract, fractions and four flavonoids from the twigs of Dorstenia angusticornis Engl. (Moraceae)

The methanolic extract (DAT), fractions (FRS) and four flavonoids, namely Gancaonin Q (1), Stipulin (2), Angusticornin B (3) and Bartericin A (4), isolated from the twigs of Dorstenia angusticornis (Moraceae), were tested for their in vitro antimicrobial activity. A total of 22 microbial cultures belonging to three Candida species, 6 Gram-positive and 13 Gram-negative bacterial species were used in this study. The inhibition zones (IZ) of the test samples against the pathogens were determined by the Agar Hole Diffusion test while the Liquid dilution method was used to determine their minimal inhibition concentrations (MIC) and their minimal microbicidal concentrations (MMC). Results indicate that DAT, compounds 3 and 4 inhibited the growth of all test pathogens. DAT, FRS 3-6, compounds 3 and 4 were both antibacterial and anticandidal. A single-dose oral toxicity performed in accordance with the OPPTS 870.1100 and OECD 401guideline showed that DAT was not toxic. Our findings provide a possible basis for the potential use of twigs from Dorstenia angusticornis in the treatment of infectious diseases.

Antimicrobial activity of the methanolic extracts and compounds from Vismia laurentii De Wild (Guttiferae)

Methanolic extracts prepared from the leaves, twigs and the roots of Vismia laurentii De Wild as well as nine compounds isolated from these crude extracts, were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and two Candida species using disc diffusion and well micro-dilution methods. The disc diffusion assay indicated that the crude extract was active against all the pathogens tested, whereas isolated compounds showed selective activities. The degree of sensitivity of the test organisms to purified compounds varied from 25 to 90%. Fridelin (8) was found to be the most active compound, while Bivismiaquinone (3) was the least active. The lowest minimum inhibition concentration (MIC) values as obtained by the micro-dilution assays were 19.53 and 1.22 microg/ml for the crude extracts and purified compounds, respectively. The lowest value for the purified compounds (1.22 microg/ml) was obtained with O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol (6) on Candida gabrata and Bacillus subtilis; 1,8-dihydroxy-6-methoxy-3-methylanthraquinone (5) on Bacillus subtilis and 6-deoxyisojacareubin (7) on Bacillus stearothermophilus. These results provide promising baseline information for the potential use of these crude extracts as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Laurentixanthones A and B, antimicrobial xanthones from Vismia laurentii

A phytochemical investigation of the constituents of the roots of Vismia laurentii has resulted in the isolation of two xanthone derivatives named laurentixanthone A (1) (6-hydroxy-3,3-dimethyl-11-(3-methylbut-2-enyl)pyrano[2,3-c]xanthen-7(3H)-one) and laurentixanthone B (2) (1-hydroxy-5,6,7,8-tetramethoxyxanthone), along with 11 known compounds: 1,7-dihydroxyxanthone, vismiaquinone, vismiaquinone B, bivismiaquinone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol, 6-deoxyisojacareubin, 1,8-dihydroxy-6-methoxy-3-methylanthraquinone, kaempferol, friedelin and stigmasterol. The structures of compounds were established by means of spectroscopic methods. Furthermore, the compounds were screened for antimicrobial activities in vitro.

Antimicrobial activity of the methanolic extract from the stem bark of Tridesmostemon omphalocarpoides (Sapotaceae)

The methanolic extract and fractions from the stem bark of Tridesmostemon omphalocarpoides were investigated for their in vitro antimicrobial properties as well as their phytochemical constituents. The stem bark was collected from Yaoundé, in the Centre Province of Cameroon. The antimicrobial activity of the extract and fractions against two Candida species and seven aerobic bacteria was evaluated on the basis of the inhibition zones (IZ) using agar hole diffusion method, the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) by the macrodilution method. The results indicated significant anticandidal and antibacterial effect of the methanolic extract and fractions against all the nine microorganisms tested. Preliminary phytochemical analysis of methanolic extract showed the presence of biologically active components namely alkaloids, steroids, tannins, saponins, phenols, polyphenols and flavonoids. The acute toxicity of the methanolic extract was also studied. This was found to be non-toxic to the inbred Wistar rats treated per os. The results of this study suggested that the stem bark of this plant could be safely used in the treatment of some infectious diseases.

Newbouldiaquinone A: A naphthoquinone-anthraquinone ether coupled pigment, as a potential antimicrobial and antimalarial agent from Newbouldia laevis

The study of the chemical constituents of the roots of Newbouldia laevis (Bignoniaceae) has resulted in the isolation and characterization of a naphthoquinone-anthraquinone coupled pigment named newbouldiaquinone A (1) together with 14 known compounds: apigenin, chrysoeriol, newbouldiaquinone, lapachol, 2-methylanthraquinone, 2-acetylfuro-1,4-naphthoquinone, 2,3-dimethoxy-1,4-benzoquinone, oleanolic acid, canthic acid, 2-(4-hydroxyphenyl)ethyl triacontanoate, newbouldiamide, 5,7-dihydroxydehydroiso-alpha-lapachone, beta-sitosterol, and beta-sitosterol glucopyranoside. The structure elucidation of the isolated compounds was established based on spectroscopic studies, notably of the 2D NMR spectra. The antimalarial activity of compound (1) against Plasmodium falciparum in vitro shows moderate chemo suppression of parasitic growth. Its antimicrobial activity against a wide range of microorganisms was 13- and 24-fold more active against Candida gabrata and Enterobacter aerogens than the reference antibiotics nystatin and gentamycin.

Xanthones from Garcinia smeathmannii (Oliver) and their antimicrobial activity

Two new xanthones, smeathxanthone A (1) (2-(3,7-dimethyl-2,6-octadienyl)-1,3,5,8-tetrahydroxyxanthone) and smeathxanthone B (2) (5,7,10-trihydroxy-2-methyl-2-(4-methylpent-3-enyl)[2H, 6H]pyrano[3,2-b]xanthen-6-one), have been isolated from the stem bark of Garcinia smeathmannii, and their structures elucidated on the basis of 1D and 2D NMR experiments. 1,3,5-Trihydroxyxanthone and 1,5-dihydroxyxanthone were also obtained. The compounds showed only modest activity against a range of bacteria and yeasts.