Study on Antibacterial Activity of Common Medicinal Plants Used to Treat Diabetes in Bangladesh

Abstract

Medicinal plants, besides having therapeutic values against diabetes mellitus may have other pharmacological actions. To know whether common antidiabetic plants in Bangladesh possess antibacterial activity, methanol extracts of them were tested against six pathogenic bacteria. Among the extracts, Coccinia indica (leaves), Gymnema sylvestre (Bark), Swertia chirata (whole part) and Syzygium cumini (seed) showed strong inhibition against Salmonella typhi, S. paratyphi A, Staphylococcus aureus and Shigella dysenteriae in disc diffusion test at the concentration of 400 μg/disc. No extract inhibited the growth of Vibrio cholerae. After that, extracts of C. indica, G. sylvestre and S. cumini were subjected to evaluate their IC50 values. The lowest IC50 value was found in C. indica against S. paratyphi A. Since inhibitory actions of C. indica, G. sylvestre, S. chirata and S. cumini were found efficient, they had been fractionated into five fractions namely hexen, diethylether, chloroform, ethylacetate and methanol. Among the fractions, methanol fraction of S. cumini effectively inhibited the growth of all four bacteria at the concentration of 400 μg/disc, whereas, S. paratyphi A was inhibited by C. indica and S. typhi by both G. sylvestre and S. chirata. However, the methanol fractions showed lesser inhibition than that of methanol extracts against the bacteria which entails the idea of synergistic action. Since methanol fractions of the four plants were the most potent their IC50, MIC and MBC values were determined. Altogether, the results showed that among the common antidiabetic plants, S. cumini had potent antibacterial activity that might be used in treating both diabetes and bacterial infections.