Effect of in vitro digestion on bioactive compounds and antioxidant activity of common bean seed coats

• Polyphenols and antioxidant activity of bean seed coats extracts were evaluated.
• Extracts were treated or untreated with in vitro digestion.
• Digestion reduced the levels of total phenols and anthocyanins.
• The antioxidant activity was not reduced after in vitro digestion.

The effects of gastrointestinal digestion on black bean (BB) and small red bean (SRB) seed coats were evaluated in treated and untreated extracts with an in vitro digestion process. The total phenols (TPs), total flavonoids (TFs), condensed tannins (CTs), monomeric anthocyanins (MAs), ABTS radical-scavenging capacity and oxygen radical absorbance capacity (ORAC) were evaluated in both groups. Anthocyanins, which appeared at 10-fold higher levels in BB than SRB (0.83 mg and 0.08 mg cyanidin 3-glucoside equivalents/g of bean, respectively) were undetectable in either extract after digestion. The results indicate that the in vitro digestion process was responsible for a reduction of the TPs, CTs and MAs in both the BB and SRB seed coats, and of TFs in the BB seed coats. However, the antioxidant activity was maintained for both groups, and even significantly increased in the BB group when measured with an ORAC assay.