Abstract
Bioactive peptides are peptides that are able to exert beneficial health effects apart from providing the nutritional aspect. In this study, bioactive peptides were produced and purified from alcalase hydrolysed Salmon skin gelatin. A gel filtration fraction, GF28, was identified as the most potent fraction. A further aim of this study was to investigate the bioactive properties including antioxidant, ACE inhibition, and anti-proliferative activities of the peptide. GF28 exhibited ACE inhibition activity of 46.5 %. Further studies elucidated GF28 acts as a competitive inhibitor of ACE. GF28 also exhibited comparable antioxidant activity to the positive control trolox (67.1 % and 67.3 % respectively). The antioxidant mechanism of GF28 mainly involved transition metal ion chelating activity and less reducing power activity. Apart from that, GF28 had poor radical scavenging activity in both hydrophobic and hydrophilic environments. GF28 also showed cytotoxic effects in hepatocellular carcinoma, HepG2 cells (IC50=0.154 mg/mL). In addition, GF28 also affected the endogenous antioxidant defence system in HepG2 cells by decreasing SOD, total glutathione and GPx activity. Catalase activity in GF28 treated HepG2 cells also increased. Anti-proliferative effects of GF28 were also observed in Caco-2 cells (IC50=0.16 mg/mL). In 0.15 mg/mL GF28 treated Caco-2 cells, intracellular and mitochondrial ROS (15.3 % and 7.8 % respectively) were significantly lower than untreated cells (32.9 % and 25.2 % respectively). Caco-2 cells treated with GF28 showed cell cycle arrest in the G1 phase as well as apoptosis. The extrinsic and intrinsic apoptosis pathway was activated with GF28. Caspase-8, caspase-3/7 and PARP were activated in the extrinsic pathway whereas caspase-9 and LaminA/C were activated in the intrinsic pathway.