Comparative antimicrobial and antioxidant activities of four medicinal plants

Abstract

Pathogenic microorganisms and oxidative stress have continuously threatened the wellbeing of humans. In this study, we determined the Minimum Inhibitory Concentration (MIC) and Minimum Bacteriocidal Concentration (MBC)/ Minimum Fungicidal Concentration (MFC) of extracts of Eugenia uniflora, Cassia sieberiana, Laportea aestuans and Dysoxylum lenticellare against methicillin resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and Candida albicans. The antioxidant activities of these extracts were also evaluated. The 50% methanol extracts were obtained by maceration at room temperature (26-33 ºC). The antimicrobial test was carried out by broth dilution assay using Streptomycin and Ketoconazole as positive controls while 50% methanol was used as the negative control. The antioxidant activities were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Antioxidant Power (FRAP) and Total Antioxidant Capacity (TAC) assays with ascorbic acid used as positive control. In antibacterial studies, E. uniflora was active against all test organisms. C. sieberiana had the lowest MIC against B. subtilis and MRSA. Dysoxylum lenticellare was only active against B. subtilis. In antifungal studies, E. uniflora and C. sieberiana were the only extracts active against C. albicans. In antioxidant studies, E. uinflora was the most active for DPPH and FRAP assays while C. sieberiana was the most active for TAC. In all antioxidant evaluations, E. uniflora was the most active followed by C. siebariana while L. aestuans was the least active. Eugenia uniflora had the best antimicrobial and antioxidant activities justifying its ethnomedicinal use in the treatment of microbial infections and free radical- induced conditions such as influenza, digestive disorders, and inflammations.

Key words: Antimicrobial, Antioxidants, Medicinal plants, Minimum inhibitory concentration.