Antioxidant capacity and sequence of peptides derived from oysters and green mussels in Vietnam

High-nutrition components and antioxidant compounds have been discovered in many marine organisms in recent years, especially oysters and mussels; but, the two bivalves have not been studied extensively in Vietnam. Therefore, both oysters and green mussels from Long Son, Vietnam were collected for investigation. Results showed that the total macronutrient contents in green mussels were greater than those of oysters, with glutamic acid being the most abundant amino acid in both oysters and green mussels at 1.35 and 1.25 g/100 g, respectively. Total relevant mineral content was 521,954 mg/100 g in oyster flesh, while that in green mussels was 496,847 mg/100 g. Specifically, the zinc content was 30.30 mg/100 g in oysters, 21.96 times more than that in green mussels (1.38 mg/100 g). Biological mixtures of peptides were obtained through enzymatic hydrolysis, and their calculated catalytic efficiencies in oysters and green mussels were 0.051 and 0.067 mg/mL/s, respectively. The antioxidant activity of these peptides was determined by IC50 values in DPPH, with 6.39 mg/mL for oysters, and 10.4 mg/mL for green mussels, and IC50 values in ABTS with 18.0 mg/mL for oysters, and 18.3 mg/mL for green mussels. The sequences of the four most abundant peptide fractions in oyster and green mussel hydrolysates were identified by LC-MS; the two fractions identified in oysters were Asn-Lys-Gln-Ala (F1) and Val-Val-Val-Asp-Val-Gly-Ile (F2), and those in green mussels were Gly-Arg-Thr-Tyr (F3), and Pro-Thr-Gln-Val-Lys-Leu (F4). Tyrosine, a powerful nucleophile, was found in F3. As a result, it is reasonable to believe that green mussels have stronger ABTS free radical scavenging activity than oysters. These results will provide a real insight for research on antioxidant processes involving biological peptides from oysters and green mussels in Vietnam.