Influence of fish protein hydrolysate-pistachio green hull extract interactions on antioxidant activity and inhibition of α-glucosidase, α-amylase, and DPP-IV enzymes

Abstract

This study investigated the effects of protease type (Alcalase, papain and pepsin), fractionation (2 and 10 kDa nominal molecular weight cutoff) and pistachio green hull (PGH) extract addition on antioxidant activity (DPPH radical scavenging and metal chelating activity), α-glucosidase, α-amylase, and dipeptidyl peptidase IV (DPP-IV) inhibitory activity of Sind sardine hydrolysates. Papain led to the highest degree of hydrolysis and antioxidant activity and the addition of PGH enhanced the bioactivity. Hydrolysates and fractions had stronger inhibition of α-amylase than α-glucosidase, and hydrolysates from papain and Alcalase were more active than those from pepsin against α-amylase. Interaction of PGH and the hydrolysates/peptidic fractions resulted in a decrease in α-glucosidase and α-amylase inhibition. The kinetics of α-amylase inhibition with papain hydrolysates and papain-PGH showed competitive inhibition. Hydrolysates and fractions also significantly inhibited DPP-IV, but PGH did not inhibit the enzyme or change the inhibitory effect of the hydrolysates and fractions (P ≥ 0.05). Furthermore, the highest surface hydrophobicity was observed for the >10 kDa fractions and the values increased by the addition of PGH to the hydrolysates. Therefore, PGH–hydrolysate interaction improved only the antioxidant capacity of the protein hydrolysates with nil or negative effects on the enzyme inhibition.