Toxicity, antimicrobial and anthelmintic activities of Vernonia guineensis Benth. (Asteraceae) crude extracts

ETHNOPHARMACOLOGICAL RELEVANCE: This study examined the antibacterial, antifungal, and anthelmintic properties of extracts obtained from the plant Vernonia guineensis, a plant commonly used in traditional Cameroonian medicine.MATERIALS AND METHODS: For in vitro studies, 10g of leaf and tuber powder from V. guineensis was extracted separately using dichloromethane, methanol and distilled water. The extracts were dried in vacuo and used for antimicrobial and anthelmintic activity studies. In the antimicrobial assay, extracts were tested against bacterial and fungal organisms including; Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii, Aspergillus fumigatus, Candida albicans and Trichophyton mentagrophytes. In the anthelmintic assay, larval and adult stages of the hookworm Ancylostoma ceylanicum and the mouse nematode Trichuris muris were used. For the acute toxicity test, male and female rats of 150-200g body weight were used in the experiment. The aqueous extract of V. guineensis tubers was administered in 4 doses of 500, 1000, 2000 and 4000mg/kg per group (n=6), respectively, and the control group received distilled water.RESULTS: The crude extracts exhibited weak antibacterial and antifungal activity except for the dichloromethane extract, which showed moderate activity against A. fumigatus (MIC=200?g/ml). In the anthelmintic assay, the organic extracts of the tubers had 100% killing efficacy against T. muris at 2mg/ml in 48h, while the aqueous extract showed no activity. The organic leaf extracts demonstrated potent activity killing 100% of the adult worms 1mg/ml in 24h. The aqueous leaf extract was active at 2mg/ml in 72h, killing 100% of the adult worms. In the acute toxicity test, V. guineensis did not produce any toxic signs or death at the maximum concentration of 4000mg/kg. CONCLUSION: Crude extracts from V. guineensis possess anthelmintic activity against T. muris with only weak antibiotic activity. Acute administration of aqueous extract from V. guineensis tubers did not produce toxic effects in rats. The absence of acute toxicity at the highest concentration tested indicates that the tea decoction from V. guineensis extract is safe at concentrations ?4000mg/kg.