Influence of molecular weight on intracellular antioxidant activity of invasive silver carp (Hypophthalmichthys molitrix) protein hydrolysates

• Invasive silver carp protein hydrolysates (SPH) were developed.
• SPH showed high in vitro antioxidant activity.
• Relation between antioxidant properties and amino acid composition was evaluated.
• Peptides <3 kDa showed higher cellular antioxidant activity.
• Peptides <3 kDa retained cellular antioxidant activity during incubation times.

Protein hydrolysates from underutilized silver carp (SPH) were prepared using Flavourzyme (F-15 to F-60) and Alcalase (A-15 to A-60) at 15, 30, 45 and 60 min, respectively. SPH F-30 and A-60 showed promising chemical-based antioxidant activity and were further fractionated according to size to evaluate caco-2 cell based antioxidant activity. F-30 and A-60 peptide fractions with <3 kDa (F-30 < 3, A-60 < 3) showed higher cell-based antioxidant activity under stressed and non-stressed conditions. Further, IC50 values of F-30 < 3 (1–3 mg/mL) was lower than A-60 < 3 fractions (4 to 12 mg/mL), indicating higher cellular antioxidant activity of F-30 < 3 compared to A-60 < 3 under all conditions. The presence of active peptides with desired amino acid sequence in F-30 < 3 compared to A-60 < 3 may have contributed to its higher cellular antioxidant activity. Overall, SPH exhibited antioxidant capacity, hence using an underutilized, invasive fish for environmental and economic gain in the form of promising functional ingredients.