ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF WHITE, GREEN AND BLACK TEA EXTRACTS

In the present study, the antioxidant and antimicrobial activities of three tea (Camellia sinensis) types (white tea WT, green tea - GT, and black tea - BT) were compared and the relationships between total phenolic, tannin and flavonoid contents were determined. Regardless of the assays used, the highest total phenolic content (313.3 +/- 1.41 mu g GAE/mg extract), total flavonoid (16.98 +/- 0.27 mu g QE/mg extract) and total tannin content (266.79 +/- 2.59 mu g TAE/mg extract) were determined in green tea extract, which also demonstrated the highest antioxidant capacity. Black tea extract showed the lowest phenolic content and antioxidant capacity. The EC50 value of DPPH scavenging activity was in the order of: ascorbic acid >GT>BHA>WT>BT>BHT. While the tea extracts exhibited antibacterial activity against Staphylococcus aureus, no inhibitory effects were observed against Escherichia coli and Salmonella enteritidis. All extracts exhibited antifungal activity against two aflatoxigenic moulds Aspergillus parasiticus NRRL 2999 and NRRL 465. The antibacterial activity of tea extracts decreased in the following order: GT>WT>BT DPPH scavenging activity strongly correlated with total phenolic content, reducing power, antimicrobial activity against S. aureus, A. parasiticus NRRL 2999, A. parasiticus NRRL 465 (P<0.05). These data suggest that green tea extract is more effective than white and black tea extracts as a potential source of natural antioxidants.