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

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), alpha-glucosidase, alpha-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 alpha-amylase than alpha-glucosidase, and hydrolysates from papain and Alcalase were more active than those from pepsin against alpha-amylase. Interaction of PGH and the hydrolysates/peptidic fractions resulted in a decrease in alpha-glucosidase and alpha-amylase inhibition. The kinetics of alpha-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.

Automated summary

This study found that adding pistachio green hull extract can enhance the antioxidant activity of Sind sardine hydrolysates under various protease types and fractionation conditions, with papain leading to the highest degree of hydrolysis and antioxidant activity. However, the addition of pistachio green hull extract had negative effects on enzyme inhibition, especially in terms of alpha-glucosidase and alpha-amylase inhibition.