Jean De Dieu Tamokou

Antimicrobial activities of methanol extract and compounds from stem bark of Vismia rubescens

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, Staphylococcus 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 microg/ml). Compounds 2 and 3 were the most active (MIC=3.12-100 microg/ml) while Staphylococcus 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.

Antioxidant and antimicrobial activities of ethyl acetate extract, fractions and compounds from stem bark of Albizia adianthifolia (Mimosoideae)

BackgroundAlbizia adianthifolia is used traditionally in Cameroon to treat several ailments, including infectious and associated diseases. This work was therefore designed to investigate the antioxidant and antimicrobial activities of ethyl acetate extract, fractions and compounds isolated from the stem bark of this plant.MethodsThe plant extract was prepared by maceration in ethyl acetate. Its fractionation was done by column chromatography and the structures of isolated compounds were elucidated using spectroscopic data in conjunction with literature data. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays were used to detect the antioxidant activity. Broth micro-dilution method was used for antimicrobial test. Total phenol content was determined spectrophotometrically in the extracts by using Folin–Ciocalteu method.ResultsThe fractionation of the extract afforded two known compounds: lupeol (1) and aurantiamide acetate (2) together with two mixtures of fatty acids: oleic acid and n-hexadecanoic acid (B1); n-hexadecanoic acid, octadecanoic acid and docosanoic acid (B2). Aurantiamide acetate was the most active compound. The total phenol concentration expressed as gallic acid equivalents (GAE) was found to vary from 1.50 to 13.49 μg/ml in the extracts. The antioxidant activities were well correlated with the total phenol content (R2 = 0.946 for the TEAC method and R2 = 0.980 for the DPPH free-radical scavenging assay).ConclusionsOur results clearly reveal that the ethyl acetate extract from the stem bark of A. adianthifolia possesses antioxidant and antimicrobial principles. The antioxidant activity of this extract as well as that of compound 2 are being reported herein for the first time. These results provide promising baseline information for the potential use of this plant as well as compound 2 in the treatment of oxidative damage and infections associated with the studied microorganisms.

Anticancer and Antimicrobial Activities of Some Antioxidant-Rich Cameroonian Medicinal Plants

Traditional remedies have a long-standing history in Cameroon and continue to provide useful and applicable tools for treating ailments. Here, the anticancer, antimicrobial and antioxidant activities of ten antioxidant-rich Cameroonian medicinal plants and of some of their isolated compounds are evaluated.The plant extracts were prepared by maceration in organic solvents. Fractionation of plant extract was performed by column chromatography and the structures of isolated compounds (emodin, 3-geranyloxyemodin, 2-geranylemodin) were confirmed spectroscopically. The antioxidant activity (AOA) was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) bleaching method, the trolox equivalent antioxidant capacity (TEAC), and the hemoglobin ascorbate peroxidase activity inhibition (HAPX) assays. The anticancer activity was evaluated against A431 squamous epidermal carcinoma, WM35 melanoma, A2780 ovary carcinoma and cisplatin-resistant A2780cis cells, using a direct colorimetric assay. The total phenolic content in the extracts was determined spectrophotometrically by the Folin–Ciocalteu method. Rumex abyssinicus showed the best AOA among the three assays employed. The AOA of emodin was significantly higher than that of 3-geranyloxyemodin and 2-geranylemodin for both TEAC and HAPX methods. The lowest IC50 values (i.e., highest cytotoxicity) were found for the extracts of Vismia laurentii, Psorospermum febrifugum, Pentadesma butyracea and Ficus asperifolia. The Ficus asperifolia and Psorospermum febrifugum extracts are selective against A2780cis ovary cells, a cell line which is resistant to the standard anticancer drug cisplatin. Emodin is more toxic compared to the whole extract, 3-geranyloxyemodin and 2-geranylemodin. Its selectivity against the platinum-resistant A2780cis cell line is highest. All of the extracts display antimicrobial activity, in some cases comparable to that of gentamycin.

Antifungal Properties of Chenopodium ambrosioides Essential Oil Against Candida Species

The essential oil of the aerial part (leaves, flowers and stem) of Chenopodium ambrosioides was obtained by hydrodistillation and its chemical composition analyzed by GC and GC/MS, which permitted the identification of 14 components, representing 98.8% of the total oil. Major components were α-terpinene (51.3%), p-cymene (23.4%) and p-mentha-1,8-diène (15.3%). The antifungal properties of this essential oil were investigated in vitro by the well diffusion and broth microdilution methods. The in vitro antifungal activity was concentration dependent and minimum inhibitory concentration values varied from 0.25 to 2 mg/mL. The in vivo antifungal activity was evaluated on an induced vaginal candidiasis rat model. The in vivo activity of the oil on mice vaginal candidiasis was not dose-dependent. Indeed, all the three tested doses; 0.1%, 1% and 10% led to the recovery of mice from the induced infection after 12 days of treatment. The effect of the essential oil on C. albicans ATCC 1663 fatty acid profile was studied. This oil has a relatively important dose-dependent effect on the fatty acids profile.

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.

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.

Antibacterial and dermal toxicological profiles of ethyl acetate extract from Crassocephalum bauchiense (Hutch.) Milne-Redh (Asteraceae)

BackgroundThe emergence in recent years of numerous resistant strains of pathogenic bacteria to a range of formerly efficient antibiotics constitutes a serious threat to public health. Crassocephalum bauchiense, a medicinal herb found in the West Region of Cameroon is used to treat gastrointestinal infections as well as liver disorders. The ethyl acetate extract from the leaves of C. bauchiense was evaluated for its antibacterial activity as well as acute and sub-acute toxicities.MethodsThe plant extract was prepared by maceration in ethyl acetate. Its phytochemical screening was done by standard methods. The broth microdilution method was used to evaluate the in vitro antibacterial activity. The in vivo antibacterial activity of a gel formulation (0.05, 1 and 2% w/v) of this extract was evaluated using a Staphylococcus aureus-induced dermatitis in a murine model. Selected haematological and biochemical parameters were used to evaluate the dermal sub-acute toxicity of the extract in rats.ResultsPhytochemical screening of the C. bauchiense extract revealed the presence of alkaloids, phenols, tannins and sterols. In vitro antibacterial activities were observed against all the tested microorganisms (MIC = 0.04-6.25 mg/ml). Formulated extract-gel (2% w/v) and gentamycin (reference drug) eradicated the microbial infection after five days of treatment. A single dermal dose of this extract up to 32 g/kg body weight (bw) did not produce any visible sign of toxicity. Also, daily dermal application of the C. bauchiense extract gel formulation for 28 days did not show any negative effect, instead some biochemical parameters such as alanine aminotransferase (ALT and AST), low density lipoprotein (LDL), high density lipoprotein (HDL) and triglycerides were significantly (p < 0.05) affected positively.ConclusionThese results indicate that the C. bauchiense ethyl acetate extract can be used safely for the treatment of some bacterial infections.

Phytochemical analysis, antimicrobial and radical-scavenging properties of Acalypha manniana leaves

AbstractAcalypha manniana (Euphorbiaceae) is a plant popularly used in Cameroon and in several parts of Africa for the treatment of various microbial diseases like diarrhea and skin infections.The present study was designed to evaluate the phytochemical composition, antimicrobial and radical-scavenging activities of A. manniana methanol leaf extract and its fractions. The methanol extract was partitioned into hexane, ethyl acetate and residual fractions and phytochemical analysis was conducted using standard methods. The broth microdilution method was used to evaluate the antimicrobial activity against nine bacterial species and four dermatophyte species. The free radical scavenging activities of the methanol extract and its fractions were evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay.The results obtained showed that A. manniana contains alkaloids, tannins, anthocyanins, flavonoids, phenols and steroids. The methanol extract as well as the hexane, ethyl acetate and residual fractions exhibited both antibacterial and antidermatophytic activities that varied between the microbial species (MIC = 0.12 – 2.04 mg/mL). These tested samples also showed high radical-scavenging activities (RaS50 = 3.34 – 4.80 μg/mL) when compared with vitamin C used as reference antioxidant (RaS50 = 1.74 μg/mL).These findings provide evidence that the studied plant possesses antimicrobial and antioxidant properties and may act as potential antioxidant for biological systems susceptible to free radical-mediated reactions.

Synthesis and antimicrobial activities of some novel thiophene containing azo compounds

Abstract A series of new thienylazothiophenes were prepared by coupling reactions of diazotized thienocoumarins with their corresponding free amines. The structures of the products 3–7 were assigned on the basis of their elemental and spectroscopic data. The HMBC and HSQC techniques were used in some cases to ascertain the structural assignments. The antimicrobial screenings of compounds 3–7 along with substituted 2-aminothiophenes 1a,b were performed against three bacteria and three fungal species and their activities compared to those of nystatin, gentamycin and ciprofloxacin used as reference drugs. It was found that the antimicrobial activities of the tested new hybrid compounds were in some cases equal or better than those of the reference drugs.