Four Antioxidant Peptides from Protein Hydrolysate of Red Stingray ( Dasyatis akajei) Cartilages: Isolation, Identification, and In Vitro Activity Evaluation

Abstract

In the work, water-soluble proteins of red stingray ( Dasyatis akajei) cartilages were extracted by guanidine hydrochloride and hydrolyzed using trypsin. Subsequently, four antioxidant peptides (RSHP-A, RSHP-B, RSHP-C, and RSHP-D) were isolated from the water-soluble protein hydrolysate while using ultrafiltration and chromatographic techniques, and the amino acid sequences of RSHP-A, RSHP-B, RSHP-C, and RSHP-D were identified as Val-Pro-Arg (VPR), Ile-Glu-Pro-His (IEPH), Leu-Glu-Glu--Glu-Glu (LEEEE), and Ile-Glu-Glu-Glu-Gln (IEEEQ), with molecular weights of 370.46 Da, 494.55 Da, 647.64 Da, and 646.66 Da, respectively. VPR, IEPH, LEEEE, and IEEEQ exhibited good scavenging activities on the DPPH radical (EC ₅₀ values of 4.61, 1.90, 3.69, and 4.01 mg/mL, respectively), hydroxyl radical (EC ₅₀ values of 0.77, 0.46, 0.70, and 1.30 mg/mL, respectively), superoxide anion radical (EC ₅₀ values of 0.08, 0.17, 0.15, and 0.16 mg/mL, respectively), and ABTS cation radical (EC ₅₀ values of 0.15, 0.11, 0.19, and 0.18 mg/mL, respectively). Among the four isolated antioxidant peptides, IEPH showed the strongest reducing power and lipid peroxidation inhibition activity, but LEEEE showed the highest Fe ²⁺-chelating ability. The present results suggested that VPR, IEPH, LEEEE, and IEEEQ might have the possibility of being an antioxidant additive that is used in functional food and pharmaceuticals.