Bioaccessibility and transport of lentil hull polyphenols in vitro, and their bioavailability and metabolism in rats

Polyphenol-rich lentil hulls are a valuable by-product. In this study, lentil hulls were subjected to simulated in vitro digestion and caco-2 cell monolayer models to assess the bioaccessibility, transmembrane transport, and a rat model to examine the bioavailability and metabolism in vivo. Polyphenols were increasingly released during the in vitro digestion, and were found to contribute to the increased antioxidant activity. Among the bioaccessible polyphenols, catechin glucoside, kaempferol tetraglucoside, procyanidin dimer and dihydroxybenzoic acid-O-dipentoside were most efficiently transported across the caco-2 membrane, and responsible for promoting in-testinal integrity as a result of enhanced expression of tight junction proteins. When ingested by rats, lentil hull polyphenols underwent extensive I and II phase metabolic reactions in vivo, including hydroxylation, methyl-ation, glucuronidation and sulfation. Overall, results of this study showed that lentil hull polyphenols are bio-accessible and bioavailable, and lentil hulls as a by-product can be a valuable ingredient for future functional foods.