Antioxidant and antimicrobial activities of white, green and black tea extracts
2013
Orak, H. H. | Yagar, H. | Isbilir, S. S. | Demirci, A. S. | Gumus, T.
In the present study, the antioxidant and antimicrobial activities of three tea (<i>Camellia sinensis</i>) 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 μg GAE/mg extract), total flavonoid (16.98±0.27 μg QE/mg extract) and total tannin content (266.79±2.59 μg 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 EC<sub>50</sub> 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 <i>Staphylococcus aureus</i>, no inhibitory effects were observed against <i>Escherichia coli</i> and <i>Salmonella enteritidis</i>. All extracts exhibited antifungal activity against two afl atoxigenic moulds <i>Aspergillus parasiticus</i> 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 <i>S. aureus</i>, <i>A. parasiticus</i> NRRL 2999, <i>A. parasiticus</i> 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.
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