The beneficial effects of the tea beverage are well-known and mainly attributed to polyphenols which, however, have poor bioaccessibility and bioavailability. The purpose of the present study was the evaluation of colon bioaccessibility and antioxidant activity of tea polyphenolic extract. An 80% methanolic extract (v/v) of tea polyphenols was obtained from green (GT), white (WT) and black tea (BT). Simulated gastrointestinal (GI) digestion was performed on acid-resistant capsules containing tea polyphenolic extract. The main tea polyphenols were monitored by HPLC-diode-array detector (DAD) method; in addition, Total Phenol Content (TPC) and antioxidant activity were evaluated. After GI digestion, the bioaccessibility in the colon stage was significantly increased compared to the duodenal stage for both tea polyphenols and TPC. Similarly, the antioxidant activity in the colon stage was significantly higher than that in the duodenal stage. Reasonably, these results could be attributable in vivo to the activity of gut microbiota, which is able to metabolize these compounds, generating metabolites with a greater antioxidant activity. Our results may guide the comprehension of the colon digestion of polyphenols, suggesting that, although poorly absorbed in the duodenum, they can exert their antioxidant and anti-inflammatory activities in the lower gut, resulting in a novel strategy for the management of gut-related inflammatory diseases.
Keywords: bioaccessibility; microbiota; nutraceutical; polyphenols; tea.