Phytochemical screening and antimicrobial activity of Olea europaea subsp. africana against pathogenic microorganisms

Abstract

Olea africana is traditionally used for treating different ailments in South Africa. This study investigates the phytochemical properties, antioxidant production and antimicrobial properties of different leaf extracts of O. africana. The ground leaves were extracted with solvents (butanol, ethanol, ethyl acetate, hexane methanol and water) of varying polarity. Antimicrobial activities against different pathogens (Bacillus cereus, Enterococcus faecalis, Moraxella catarrhalis, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, Candida albicans, Candida tropicalis and Cryptococcus neoformans) were evaluated by the agar well diffusion method and the minimum inhibitory concentration (MIC) of each extract was assessed. The antioxidant potential of each extract was determined by free radical (2, 2-diphenyl-1-picrylhydrazyl) scavenging activity. The MIC values against test bacteria ranged between 31.2 and 250 µg/mL. Phytochemical screening revealed the presence of alkaloids, flavones, flavonoids, steroids tannins, and terpenoids compounds. The antioxidant IC50 value for each solvent: butanol, ethanol, ethyl acetate, hexane methanol and water is 87.56, 82.45, 95.47, 92.25, 91.93 and 107.29 µg/mL respectively. The antioxidant activities of the crude extracts were found to depend on the concentration used with extract from ethanol exhibiting the highest antioxidant activity. Camphor and oleuropein were identified with GC-MS as bioactive compounds present in the crude extracts of O. africana. The results obtained from this study showed that extracts of Olea africana are a potential source of antioxidant and antimicrobial agents.