Antimicrobial and antioxidative effects of Ugandan medicinal barks

Abstract

Despite a rich tradition of medicinal plants use by local communities in Uganda their direct antimicrobial effectives together with potential to protect human health against diseases induced by oxidative stress are still poorly documented. The aim of this study is to investigate the in vitro antimicrobial and total antioxidative activities of barks from five tree species selected using information on their traditional use by Karamojong healers in Uganda. The antimicrobial activity of crude ethanol extracts of Fagaropsis angolensis (Engl.) H. M. Gardener (Rutaceae), Trichilia prieuriana A. Juss. (Meliaceae), Turraea floribunda Hochst. (Meliaceae), Warburgia salutaris Sprague (Canellaeceae) and Zanthoxylum chalybeum Engl. (Rutaceae) were tested against four bacteria and one yeast species using the broth microdilution method. The total antioxidative activity was determined by 2,2-diphenyl-1- picrylhydrazil free radical scavenging assay. It was found that the extract of F. angolensis possess the strongest antimicrobial activity inhibiting growth of Staphylococcus aureus and Candida albicans with minimum inhibitory concentrations of 64 and 32 μg/ml, respectively. Among all plants tested, W. salutaris showed the most promising antioxidative properties (IC₅₀ = 6.59 μg/ml). As a result of this study, F. angolensis and W. salutaris possessed significant antimicrobial and antioxidative effects which indicates prospective pharmacological properties of both species.

Key words: Antimicrobial activity, total antioxidative activity, crude extracts, medicinal plants, Uganda.