In vitro antioxidant and antimicrobial activity of Prunus africana (Hook. f.) Kalkman (bark extracts) and Harrisonia abyssinica Oliv. extracts (bark extracts): A comparative study

Background:  Plants are new sources of antibacterial agents, hence the need to determine and evaluate the antibacterial properties, antioxidant activity and gas chromatography – mass spectrometer (GC-MS) profile of medicinal plants. Methodology:  In this study, sequential extraction of  Prunus africana  and  Harrisonia abyssinica  was used to obtain ethyl acetate and methanol extracts. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), whereas the total phenolic and total flavonoid contents were estimated using Folin-Ciocalteu and aluminium chloride, respectively. Antibacterial properties of the extracts against  Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and  Candida albicans  were estimated using the disc diffusion method and compared against streptomycin. Results:  Screening of crude methanolic extracts revealed the presence of secondary metabolites which was further confirmed by Fourier transform infrared (FT-IR) characterisation that revealed the presence of H-bonded OH functional groups. The extracts revealed that  P. africana  had a higher total phenolic and total flavonoid contents compared to  H. abyssinica . Methanolic extracts of both plants had moderate activity against selected microorganisms and both inhibited DPPH radical scavenging activity. GC-MS analysis of  P. africana  and  H. abyssinica  extracts revealed the presence of several phytochemicals that have been reported to have medicinal uses. Total phenolic and flavonoid contents showed positive correlations with the DPPH radical scavenging activity and negative correlations with EC 50 . Conclusion: Prunus africana  and  H. abyssinica  extracts had moderate antimicrobial properties against the selected microorganisms because of the presence of secondary metabolites.