An in vitro study of the antibacterial properties of selected plant species found in Adamawa State, Nigeria

Abstract

The antibacterial activity of plant extracts compared to a known antibiotic (ampicillin) was evaluated against ten gram-negative and gram-positive bacteria which can infect humans. In addition, the efficacies of different extraction methods were studied. Soxhlet, cold aqueous, and hot aqueous extractions were used in this study. Moreover, extracts from the following plants were utilized: Zingiber officinale (ginger); and the leaves of Agave americana (agave), Musa acuminata (banana), Mangifera indica (mango), Azadirachta indica (neem), and Eucalyptus sp. (Eucalyptus). The most antibacterial activities were observed for the extracts of Eucalyptus sp. and Mangifera indica, which inhibited 60% and 50% of the tested bacterial species, respectively. There was significant activity against gram-positive bacteria. Agave and banana extracts, on the other hand, did not demonstrate any antibacterial activity. The most susceptible species of bacteria tested was Micrococcus luteus with a total of 8 out of 17 different plant/preparation combinations affecting it. The least susceptible species were Escherichia coli, Proteus vulgaris, Salmonella typhi & Klebsiella pneumoniae. Soxhlet extraction provided the highest number of zones of inhibition by its bioactive compounds of the three extraction methods.