Relationship between antioxidative potential and amino acids composition of the bioactive peptides prepared from Indian squid Uroteuthis (Photololigo) duvaucelii (d’Orbigny, 1835) using alcalase

Abstract

Biopeptides derived from fish protein hydrolysates are gaining popularity as active ingredients in functional foods. In this study, squid protein hydrolysates (SPH) prepared from Uroteuthis (Photololigo) duvaucelii, using alcalase and their biopeptides fractionated using ultrafiltration were investigated for their antioxidant properties in relation to the changes in
their amino acid profiles. Squid mantle hydrolysed within 30 min with a degree of hydrolysis (DH) of 13.7%. SPH had 89% 2, 2-diphenyl-1- picrylhydrazyl (DPPH) inhibition, 94% 2, 2-azino-bis-(3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) inhibition and 96% hydroxyl inhibition at 10 mg ml-1 concentration. In the squid peptides, DPPH inhibition increased with the decrease in the molecular size of peptides from 51% to 95% (3 Ka), ABTS radical inhibition was <42% for peptides
with >5KDa size and >95% for peptides with <5KDa. Hydroxyl radical inhibition increased from 75-98% with decrease in molecular size. Increase in glycine, alanine, leucine and taurine was noticed in peptides with MW <5KDa along with a decrease in methionine and arginine. Histidine, asparagine and tyrosine had also contributed to the activities of peptides with MW 3-5 KDa sizes. This study indicated that peptides with MW <5KDa had more free radicals scavenging activities with more hydrophobic amino acids, tyrosine and taurine which are mainly responsible for antioxidative properties. Therefore, squid peptides with MW <5KDa prepared using alcalase have potential to serve as nutraceuticals.