In Vitro Antioxidant and Antimicrobial Activities of Methanol Leaf Extract and Fractions of Afzelia bellaHarms (Fabaceae)

Abstract

Afzelia bella Harms (Fabaceae), a plant widely distributed in Africa, is used in traditional medicine for varied disease conditions including the treatment of topical skin infections. The present study investigated the antimicrobial and antioxidant activities of the methanol extract and various solvent fractions of the leaves of the plant. The methanol leaf extract was partitioned to yield petroleum ether, chloroform, ethyl acetate and residual aqueous fractions. Total phenol and flavonoid contents, radical scavenging activity and ferric reduction antioxidant power (FRAP) were determined by spectrophotometry, while antimicrobial activity and minimum inhibitory concentration (MIC) of the extract and fractions were determined using agar-well diffusion and agar dilution methods, respectively against clinical bacterial isolates of Bacillus subtilis, Escherishia coli, Klebsiella pneumoniae, Staphylococcus aureus, and fungi, Aspergillus flavus, Candida parapsilosis, Microsporium audiounii. Bacillus subtilis was the most susceptible among the bacterial strains tested, while Microsporium audiounii was the most susceptible fungus. The alcoholic extract and all solvent fractions demonstrated a concentration dependent antimicrobial activity with inhibition zone diameter range of 7.5 to 35.0 mm. MIC ranged from 0.1 - 8 mg/ml and activity was highest in ethyl acetate fraction with MIC of 0.1 mg/ml. FRAP ranged from 0.161 - 0.319 mmol Fe2+/g extract and was highest in the ethyl acetate fraction. These results give an indication that A. bella leaf has high antioxidant and antimicrobial activities and support the folkloric claim of the therapeutic potential of the plant.

Keywords: antioxidant, antimicrobial, ethnomedicine, Afzelia bella, Fabaceae