ANTIBACTERIAL ACTIVITY OF SIX MEDICINAL PLANTS USED IN TRADITIONAL MEDICINE GROWING IN BANGLADESH

The antibacterial activity of the hexane, methanol, and water extracts of Tamarindus indica, Azadirachta indica, Cucumis sativus, Eucalyptus camaldulensis, Switenia mahagoni, and Psidium guajava extensively used in traditional medicine were investigated. The disc diffusion assay method was used for the evaluation of the antibacterial activity of these extracts against 11 bacteria species. Kanamycin (30 µg /disc) was used as a standard antibacterial agent. The results indicated that all the six plant species (not all extracts) showed a moderate antibacterial activity against a wide variety of gram positive and gram negative bacteria at a concentration of 500 µg/disc. The hexane extract of Eucalyptus camaldulensis and Switenia mahagoni revealed the moderate antibacterial activity against 10 and 6 bacteria respectively with zone of inhibition of 10-19 mm. The methanol extract of Eucalyptus camaldulensis, Psidium guajava, and Switenia mahagoni also exhibited antibacterial activity against 6, 4 and 5 bacteria respectively with a zone of inhibition of 9-15 mm whereas the water extract of Azadirachta indica and Cucumis sativus was only active against only two bacterial strains with zone of inhibition of 9-12 mm at the concentration of 500 µg/disc. The results of this study support the traditional uses of these medicinal plants as antibacterial agents.