Quantification of tannins, antioxidant capacity and antibacterial activities of stem extracts of avicennia marina (l)

Abstract

Majority of regular synthetic antibiotics are in the process of being labeled out-dated owing to multi drug resistance among pathogens. Consequently researchers are devoting interest towards identification and isolation of potent antibacterial compounds from available herbal sources. Aim: The present study was aimed at evaluation of tannin levels, antioxidant potential and antibacterial activity of Avicennia marina L (AM) extracts on selected Gram positive and Gram negative bacterial species. Methods: Stem extracts prepared in different solvents in the order of increasing polarity (ethyl acetate, acetone, ethanol and methanol) were subjected to – quantification of tannins by Folin-Denis method, antioxidant capacity by ABTS and Blue Cro5 method and antibacterial activity by agar well diffusion method against selected bacterial species. The zones of inhibition obtained were measured and the results were statistically analysed. Results: Tannin level was found to be significantly high in methanol extract followed by that in ethanol, acetone and ethyl acetate. Extract in all the solvents showed antioxidant activity. However, extracts in methanol and ethanol exerted higher potentials. Like wise, extracts in all the solvents showed various degrees of antibacterial activity against the test cultures used. The methanol extract on Bacillus subtilis, Staphylococcus aureus and Streptococcus pyogens exhibited higher activity than that of Gentamicin. Conclusions: The present experimental data reveals that the stem of AM is rich in tannins and exhibits potential antioxidant and antibacterial activities. A comparative analysis is also provided with respect to the solvent used for the study of bioactivities.