EVALUATION OF ANTIOXIDANTS, TANNINS AND ANTIBACTERIAL ACTIVITY OF GREEN TEA AND BLACK TEA AGAINST HUMAN PATHOGENIC BACTERIAC.M. LUBNA GHAZIA1AND A.GHOUSIA NISHAAbstract The polyphenols present in tea are primarily responsible for the beneficial healthful properties, while the flavonoids have antioxidant, anti-inflammatory, anti-allergic and antimicrobial effects. The present study was aimed to evaluate the antioxidants, tannins (oxidized polyphenols) and also the antibacterial activity of green tea and black tea with three different extracts (methanol, ethanol and aqueous) against 11 human pathogenic bacteria (Staphylococcus aureus, Micrococcus luteus, Listeria monocytogenes, Bacillus cereus, Vibrio cholerae, Salmonella typhi (A), Shigella sonnei, Proteus vulgaris, Klebsiella pneumoniae, Escherichia coli, Enterobacter sp). The green tea extracts showed better antibacterial activity against broad spectrum of pathogenic human bacteria, while black tea extracts showed least activity. Qualitative assay was positive for antioxidants in all extracts of both green tea and black tea. Free radical scavenging activity of green tea was higher than that of black tea. Total tannin content was highest in the green tea extracts and least in black tea extracts. Since green tea extracts showed maximum antioxidants, tannin content and antibacterial activity, it can be used as complementary medicine in treating diseases caused by multidrug resistant strains of pathogenic bacteria.
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