Jules-Roger Kuiate

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.

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 and antioxidant properties of methanol extract, fractions and compounds from the stem bark of Entada abyssinica Stend ex A. Satabie

BackgroundThe aim of this study was to evaluate the antimicrobial and antioxidant activities of the methanol extract, fractions and isolated compounds from Entada abyssinica stem bark, plant used traditionally against gastrointestinal infections.MethodsThe methanol extract of E. abyssinica stem bark was pre-dissolved in a mixture of methanol and water, and then partitioned between n-hexane, ethyl acetate and n-butanol. The ethyl acetate portion was fractionated by column chromatography and the structures of isolated compounds elucidated by analysis of spectroscopic data and comparison with literature data. Antimicrobial activity was assayed by broth microdilution techniques on bacteria and yeasts. The antioxidant activity was determined by DPPH radical scavenging method.ResultsFour known compounds [(5S,6R,8aR)-5-(carboxymethyl)-3,4,4a,5,6,7,8,8a-octahydro-5,6,8a-trimethylnaphthalenecarboxylic acid (1), methyl 3,4,5-trihydroxybenzoate (2), benzene-1,2,3-triol (3) and 2,3-dihydroxypropyltriacontanoate (4)] were isolated. Compared to the methanol extract, fractionation increased the antibacterial activities of the n-hexane and ethyl acetate fractions, while the antifungal activities increased in ethyl acetate, n-butanol and aqueous residue fractions. The isolated compounds were generally more active on bacteria (9.7 to 156.2 μg/ml) than yeasts (78.1 to 312.5 μg/ml). Apart from compound 1, the three others displayed DPPH· scavenging activity (RSa), with RSa50 values of 1.45 and 1.60 μg/ml.ConclusionThe results obtained from this study support the ethnomedicinal use of E. abyssinica in the treatment of gastrointestinal infections and the isolated compounds could be useful in the standardisation of antimicrobial phytomedicine from this plant.

Substituted 2-aminothiophenes: antifungal activities and effect on Microsporum gypseum protein profile

The increasing recognition and importance of fungal infections, the difficulties encountered in their treatment and the increase in resistance to antifungal agents have stimulated the search for therapeutic alternatives. The objective of this study was to evaluate the antifungal activities of three substituted 2‐aminothiophenes (1, 2 and 3) against some fungal species. The synthesis of substituted 2‐aminothiophenes was carried out through the most versatile synthetic method developed by Gewald et al. The antifungal activity was performed against yeast, dermatophytes and Aspergillus species using the broth microdilution method. The effect of these aminothiophenes was examined on the protein content and profile. Compound 2 was the most active (MIC varying from 2.00 to 128 μg ml−1). All the three substituted 2‐aminothiophenes had a relatively important dose‐dependent effect on Microsporum gypseum protein profile and content. These compounds affected the structure and dye fixation of macroconidia of this fungus. The overall results indicate that the tested substituted 2‐aminothiophenes can be used as precursors for new antifungal drugs development.

Acute and sub-acute toxicity of the methanolic extract of Pteleopsis hylodendron stem bark

ETHNOPHARMACOLOGICAL RELEVANCE Pteleopsis hylodendron is one of the most popular medicinal plants in Cameroon where it is used to treat measles, chickenpox, sexually transmitted diseases, female sterility, liver and kidney disorders as well as dropsy. To date there is no documented evidence corroborating its safety. This study thus aimed to determine the toxicity profile of the methanolic extract of Pteleopsis hylodendron. MATERIALS AND METHODS The acute and sub-chronic toxicity of the methanolic extract of Pteleopsis hylodendron were investigated by employing established methods. The acute toxicity study was done by administering single doses (2-8 g/kg body weight) of plant extract to adult mice. For the sub chronic toxicity study, doses (85-680 mg/kg bw) of plant extract were administered daily to adult rats during 28 days after which the effect on organs, the hematological and biochemical parameters was assessed. RESULTS In mice, single oral administrations of the methanolic extract of Pteleopsis hylodendron caused dose-dependent general behaviour adverse effects and mortality. The LD50 values were 3.00 and 3.60 g/kg bw for males and females respectively. In rats, daily single oral doses of the methanolic extract of Pteleopsis hylodendron provoked significant (p < 0.05) growth retardation in rats at all tested doses after 28 days of dosing. Haematological parameters showed a significant decrease in white blood cells count and significant increases red blood cells count; irrespective of the sex, all biochemical parameters studied, except triglycerides significantly (p < 0.001) increased with dose. However, a dose-dependent significant (p < 0.007) increase in HDL was observed only in male rats. Increases in liver enzymes (ALT and AST), proteins and creatinine levels correlate the observed histopathological damages (i.e. inflammation and vascular congestions) in the liver and kidneys. CONCLUSIONS The overall results of this study indicate that the methanolic extract of Pteleopsis hylodendron stem bark possesses hepatotoxic and nephrotoxic effects at doses ≥ 85 mg/kg bw, suggesting that this plant should be used with caution.

Aromatic Plants of Tropical Central Africa IV. Essential Oils of Eupatorium odoratum L. from Cameroon and Congo

ABSTRACT The chemical composition of the essential oils, which was obtained from the leaves of Eupatorium odoratum L. collected in Cameroon and the Congo, were examined by capillary gas chromatography and combined GC/MS. The two oils were distinguished by the presence of C12 compounds rarely found in essential oils: pregeijerene and geijerene represent 34.1% of the essential oil obtained from the leaves collected in Cameroon (Sample A) and 19% of the one from the Congo (Sample B). Besides these compounds, oil A contained mainly α-pinene (14.3%) and γ-muurolene (9.8%); whereas, oil B was characterized by a high content of aromatic compounds (up to 40%) with p-cymene (22.2%) and thymyl acetate (15.8%) being the most dominant.

Anthocleistenolide, A New Rearranged Nor-Secoiridoid Derivative from the Stem Bark of Anthocleista vogelii

A new rearranged nor-secoiridoid, anthocleistenolide ( 1), along with the known 1-hydroxy-3,7-dimethoxyxanthone ( 2), 1-hydroxy-3,7,8-trimethoxyxanthone ( 3), 7 alpha-hydroxysitosterol ( 4) and sitosterol 3- O-beta- D-glucopyranoside ( 5), were isolated from the stem back of Anthocleista vogelii. Their structures were elucidated on the basis of spectral studies and comparison with published data. Compounds 1 - 3 and 5 were evaluated for their antibacterial and antifungal activities. Relatively low anti-staphylococcal (MIC = 200 microg/mL against Staphylococcus aureus) and anti-enterococcal (MIC = 100 microg/mL against Enterococcus faecalis) activities were observed for 1, while compounds 2 and 3 were active against Candida parapsilosis (MIC = 200 microg/mL for 2 and 25 microg/mL for 3). Compound 5 was inactive against all the bacterial and fungal species used.

Composition of the essential oils from the leaves of two varieties of Aspilia africana (Pers.) C. D. Adams from Cameroon

Four essential oil samples obtained by hydrodistillation from the leaves of Aspilia africana var. africana and a corresponding sample of A. africana var. ambigua were analysed by GC and GC–MS. The two varieties were poor in essential oil content (<0.1%). The qualitative composition of the essential oils was found to be quite similar, irrespective of the area and date of plant collection. Marked differences were, however, observed in the quantitative composition of the oils from the two varieties. As far as A. africana var. africana is concerned, two oil samples from Bafoussam were rich in sesquiterpenes (88% and 94%) with germacrene-D (45% and 54%) as the major component, while two oil samples from Yaounde contained mainly monoterpenes (63% and 48%) with α-pinene (39% and 27%) as the most abundant component. The variety A. africana var. ambigua afforded an essential oil rich in monoterpenes (54%) with limonene (23%) and α-pinene (22%) as predominating components. Finally, the insect antijuvenile hormone precocene I was found to be present in all samples of the two varieties. Copyright

Antidiarrheal activity of extracts and compound from Trilepisium madagascariense stem bark.

Objective: The present study was performed to evaluate the preventive and curative antidiarrheal effects of the methanol extract, fractions and compound from the stem bark of Trilepisium madagascariense in rats. Materials and Methods: The methanol extract from the stem bark of T. madagascariense, its fractions (n-hexane, ethyl acetate, n-butanol and aqueous residue) and compound (obtained from further column chromatography of the ethyl acetate fraction) were evaluated for the antidiarrheal activity in rats. These test samples (at 100, 200 and 400 mg/kg for the extract and fractions and 2.5 mg/kg for compound) were assayed on the latent periods, purging indices and fecal frequencies in castor oil-induced diarrhea. Gastrointestinal transit and castor oil-induced enteropooling assays were conducted. Shigella-induced diarrhea was assayed. Blood chemistry and fecal Shigella load were examined. Results: The fractionation of the ethyl acetate fraction from the methanol extract of T. madagascariense afforded a known compound [isoliquiritigenin (1)]. Compound 1 increased the latent period of diarrhea induction (179.40 min) compared to the saline control (60.80 min). The purging indices, fecal frequencies and intestinal enteropooling decreased with an increase in the dose of test samples. The blood cell counts, sera creatinine and fecal Shigella load decreased significantly (P ≤ 0.05) in the plant extract-treated rats compared to the saline control. Conclusion: The results of our study, being reported for the first time, provide clear evidence that the methanol extract, fractions and isoliquiritigenin from T. madagascariense stem bark possess antidiarrheal activities.

Composition of the essential oils from the leaves of Microglossa pyrifolia (Lam.) O. Kuntze and Helichrysum odoratissimum (L.) Less. growing in Cameroon

Four essential oil samples obtained by hydrodistillation from the leaves of Microglossa pyrifolia (Lam.) O. Kuntze and Helichrysum odoratissimum (L.) Less., respectively, were analysed by GC and GC–MS. The main constituents of the leaf oil of M. pyrifolia were found to be (E)-β-farnesene (78% and 73%) and β-caryophyllene (11% and 14%), whereas those of H. odoratissimum were α-Pinene (47% and 41%), β-caryophyllene (14% and 5%) and α-curcumene (4% and 20%). Copyright