Antioxidant and Antimicrobial Effects of Aqueous and Ethanolic Extracts of Selected Medicinal Plants from Southern Nigeria

Abstract

Several indigenous and forgotten plants in the southern parts of Nigeria according to folklore possess many medicinal properties. Ethanol and aqueous extracts from six (6) of such plants namely Boerhavia diffusa; Datura stramonium; Cassia occidentalis; Scoparia dulcis; Euphorbia hirta and Baphia nitida from the southern Nigeria State of Akwa-Ibom were evaluated for both phytochemical composition and antimicrobial activities. The antioxidant activity of the extracts was determined by the DPPH inhibition method. Both the ethanolic and aqueous extracts of all the plants indicated the presence of flavonoids while the ethanolic extracts of all the plants indicated that tannins and alkaloids were present. Cassia occidentalis and AOU, indicated relatively the highest DPPH scavenging activity at lowest concentrations (0.03125 mg/ml) with AOU indicating 71.22 mg/ml an equivalence of 87% performance with respect to ascorbic acid. Results showed that when tested against Staphylococcus aureus, Streptococcus pyogenes, Salmonella typhi bacteria, the average inhibition zones ranged from 10.5-18.7 mm,10.5-18.3 mm, 10-19 mm respectively, with the ethanolic extracts, in general, showing the highest inhibition. Interestingly none of the plants showed inhibition against Klebsiella pneumoniae. With respect to fungus Candida albican, where there was activity, the inhibition zone was 10-15.3 mm. Ethanolic extract of Euphorbia hirta indicated the highest inhibition of 19 mm against Salmonella typhi.