Selenium-containing green tea has higher antioxidant and prebiotic activities than regular green tea

The effects of selenium-containing green tea (SGT: 1.4 mg selenium/kg) and China green tea (CGT: 0.13 mg selenium/kg) on the in vitro growth of lactobacilli and bifidobacteria were investigated using pure and mixed cultures. SGT had significantly higher phenolic contents (TPC), higher reducing activity, higher DPPH free-radical scavenging activity, and higher ferrous-ion chelating activity (P <0.05-0.0001) than CGT. The addition of aqueous extracts from CGT to Mann-Rogosa-Sharpe (MRS) broth at 10% and 25% (v/v) resulted in small but nonsignificant (P > 0.05) increases in the numbers of Lactobacillus rhamnosus and Bifidobacterium breve over the control incubations (without tea). Addition of 10% and 25% of SGT extract resulted in a significant increase (P <0.05-0.0001) in the number of lactobacilli and bifidobacteria recovered from batch fermentation while CGT did not increase the number of bifidobacteria. The higher prebiotic activity of SGT over CGT may be related to the higher TPC or minerals, notably selenium or a combination of these factors. To test whether selenium itself has an effect on bacterial growth, Na-selenite and Na-selenate were added alone or in combination with CGT to the MRS broth containing pure culture of L rhamnosus. Growth of this bacterium was enhanced relative to the control incubation of MRS only. When added in combination with CGT, Na-selenate was more effective at enhancing the growth of L rhamnosus than Na-selenite. The prebiotic effect of SGT could be largely explained by its selenium content. (C) 2008 Elsevier Ltd. All rights reserved.