Squid gelatin hydrolysates with antihypertensive, anticancer and antioxidant activity

Gelatin obtained from giant squid (Dosidicus gigas) inner and outer tunics was hydrolyzed by seven commercial proteases (Protamex, Trypsin, Neutrase, Savinase, NS37005, Esperase and Alcalase) to produce bioactive hydrolysates. The Alcalase hydrolysate was the most potent angiotensin-converting enzyme (ACE) inhibitor (IC50 = 0.34 mg/mL) while the Esperase hydrolysate showed the highest cytotoxic effect on cancer cells, with IC50 values of 0.13 and 0.10 mg/mL for MCF-7 (human breast carcinoma) and U87 (glioma) cell lines, respectively. The radical scavenging capacity of gelatin increased approximately 3-fold for Protamex, Neutrase and NS37005 hydrolysates and between 7 and 10-fold for Trypsin, Savinase, Esperase and Alcalase hydrolysates. Trypsin, Savinase, Esperase and Alcalase hydrolysates had a metal chelating capacity above 80% whereas Protamex, Neutrase and NS37005 hydrolysates registered less than 25%. The antioxidant activity measured by FRAP (ferric ion reducing power) was largely unaffected by the enzyme used, increasing approximately 2-fold for all hydrolysates. The most active hydrolysates (Alcalase and Esperase) were comprised mostly of peptides with molecular weights ranging from 500 to 1400 Da, however, a clear relationship between bioactive properties and molecular weight distribution of all the hydrolysates was not fully established.