In Vitro Antioxidant Activities of Enzymatic Hydrolysate from Schizochytrium sp. and Its Hepatoprotective Effects on Acute Alcohol-Induced Liver Injury In Vivo.

Schizochytrium protein hydrolysate (SPH) was prepared through stepwise enzymatic hydrolysis by alcalase and flavourzyme sequentially. The proportion of hydrophobic amino acids of SPH was 34.71%. The molecular weight (MW) of SPH was principally concentrated at 180-3000 Da (52.29%). SPH was divided into two fractions by ultrafiltration: SPH-I (MW < 3 kDa) and SPH-II (MW > 3 kDa). Besides showing lipid peroxidation inhibitory activity in vitro, SPH-I exhibited high DPPH and ABTS radicals scavenging activities with IC50 of 350 µg/mL and 17.5 µg/mL, respectively. In addition, the antioxidant activity of SPH-I was estimated in vivo using the model of acute alcohol-induced liver injury in mice. For the hepatoprotective effects, oral administration of SPH-I at different concentrations (100, 300 mg/kg BW) to the mice subjected to alcohol significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and hepatic malondialdehyde (MDA) level compared to the untreated mice. Besides, SPH-I could effectively restore the hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities and glutathione (GSH) level. Results suggested that SPH was rich in biopeptides that could be exploited as antioxidant molecules against oxidative stress in human body.

A specific antioxidant peptide: Its properties in controlling oxidation and possible action mechanism.

Marine byproducts have become popular research themes due to their biological significance. The black sharkskin protein hydrolysate-based antioxidant peptides were firstly investigated in this study. The black sharkskin-derived novel antioxidant peptide demonstrating 81.05% free radical scavenging activity to ABTS at 500 µg/mL, was identified to be Ala-Thr-Val-Tyr (ATVY). The crucially antioxidant interaction site of ATVY action on ABTS was determined to be Tyr in the N-terminal. ATVY reacted with ABTS to generate polyphenol-derived adducts which subsequently degraded into a purple compound. The MS/MS showed it was formed by covalently bonding through the phenol group of ATVY to the N group of ABTS. The free radical scavenging kinetics of ATVY on ABTS demonstrated a two-phase reaction process. These findings reveal the action mechanism of ATVY on ABTS, implying ATVY can be incorporated in the production of antioxidant food additives.