Non-gastrointestinal-hydrolysis enhances bioavailability and antioxidant efficacy of casein as compared with its in vitro gastrointestinal digest

Abstract

In this study, casein peptides prepared by alcalase-hydrolysis were originally compared with those prepared by in vitro gastrointestinal digestion, on oral bioavailability and in vitro antioxidative efficacy. Two models including simulated gastrointestinal digestion and Caco-2 cell monolayer were applied to prepare residual peptides for the bioavailability assays. Trolox equivalent antioxidant capacity (TEAC) and oxygen radical antioxidant capacity (ORAC) were employed to detect in vitro antioxidant activities, while oxidative damage model of HepG2 cells was adopted to evaluate cellular antioxidant efficacy. Alcalase hydrolysate exerted stronger potentials to produce bioavailability and in vitro antioxidant efficacy, as compared with gastrointestinal digest. Especially, low-molecular-weight fraction of alcalase hydrolysates had excellent residual antioxidant activity by TEAC and ORAC, as well as hepatic cytoprotection against hydrogen peroxide. Enzymatic specificity of alcalase and molecular weights of peptides might play important roles on the stability of antioxidant activity during in vitro digestion and absorption, and producing real antioxidative efficacy in vivo.