Total phenolic contents and antioxidant activities of selenium-rich black tea versus regular black tea

Abstract

Two black aqueous tea extracts of Camellia sinensis, (seleniumrich black tea (Se-BTE) and regular black tea (R-BTE)) were assessed for their total phenolic content (TPC) and antioxidant properties. Aqueous tea extracts were prepared using different extraction temperature and time. TPC was measured using the Folin-Ciocalteu method, while antioxidant activity was measured by ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1- picrylhydrazyl (DPPH) assays. The R-BTE showed significantly higher TPC (P < 0.05) and antioxidant activity (P < 0.05) than the Se-BTE, which may be due to these being different cultivars, or differences in growing conditions. Our findings demonstrate that both extraction temperature and time are important determinants of extracted TPC and antioxidant activities of these teas. In addition and in contrary to our expectations, the high level of organic selenium in black tea did not enhance the antioxidant activity when compared with black tea containing very low level of organic selenium. Other elements and minerals may contribute to the high antioxidant activity detected in the regular black tea.