Abstract: Oyster enzymatic hydrolysate (OE) was fractionated by ultrafiltration into three fractions: OE-I (< 5 kDa), OE-II (5–10 kDa) and OE-III (> 10 kDa). The in vitro antioxidant activities of the fractions were evaluated in terms of their 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and superoxide anion radical scavenging capacity and ferrous ion chelating capacity. Then, the effect of different doses of OE-I on the lifespan, acute oxidative stress, thermal stress, antioxidant enzyme activities, reactive oxygen species (ROS) accumulation and cell apoptosis of Caenorhabditis elegans was investigated, and the expression levels of lifespan-related genes were measured to unravel the anti-aging mechanism of OE-I. The results showed that OE-I had the strongest antioxidant activity among the three fractions, and that high-dose of OE-I significantly prolonged the lifespan of C. elegans (P < 0.01). The activities of superoxide dismutase (SOD) (P < 0.05), catalase (CAT) and glutathione peroxidase (GSH-Px) (P < 0.01) were significantly increased and the accumulation of ROS and cell apoptosis were decreased. In addition, the expression of the skn-1, daf-16, sod-3 and mtl-1 genes were up-regulated, while the expression of the daf-2 and age-1 genes were down-regulated, suggesting improved stress resistance of C. elegans. To sum up, OE-I can be used as a functional food base material for anti-oxidation and anti-aging.

Key words: oyster peptides; Caenorhabditis elegans; daf-16 gene; antioxidant; anti-aging