Antioxidant and antidiabetic properties of gelatin hydrolysate fractions derived from bigeye snapper processing byproducts

Gelatin hydrolysates derived from bigeye snapper processing byproducts with antioxidant and DPP-IV inhibitory activities were prepared, including skin gelatin hydrolysates with alcalase (GHSK-AL) and papain (GHSK-PA), and bone gelatin hydrolysates with alcalase (GHB-AL) and papain (GHB-PA). Physicochemical and bioactivity properties, as well as peptide isolation and characterization, were carried out. The obtained gelatin hydrolysates exhibited high protein contents (90.75-98.42%) and degree of hydrolysis (DH) ranging from 49.41% to 73.25%. Skin gelatin hydrolysates yielded higher amounts and exhibited higher DH than bone gelatin hydrolysates. Crude hydrolysates (GHSK-AL, GHSK-PA, GHB-AL, and GHB-PA) exhibited DPPH, ABTS, OH, and H 2 O 2 radical-scavenging activities and DPP-IV inhibitory activity, ranging from 1.32-2.49 mg/mL, 2.06-3.25 mg/mL, 0.18-1.58 mg/mL, 14.27-17.64 mg/mL, and 2.41-4.27 mg/mL, respectively. These crude hydrolysates were fractionated using ultrafiltration membranes (UF) with cut-offs of >10, 3-10, 1-3, and <1 kDa, and antioxidant and DPP-IV inhibitory activities were determined. Based on bioactivities, the 4 selected UF fractions (1-3 kDa and <1 kDa GHB-AL, and 3-10 kDa and <1 kDa GHSK-PA) were subjected to cytotoxicity testing in Caco-2 cells and Sephadex G-25 gel filtration chromatography for peptide isolation. The 47 potential peptides, with molecular weights ranging from 839 to 1520 Da and peptide lengths of 9-16 amino acids, were identified by LC-Q-TOF-MS/MS analysis.