Abstract: Hydroxyproline is a characteristic component of collagen and its existence in the peptide sequence enables collagen-derived oligopeptides to have high resistance to peptidase or protease. Oral hydroxyproline still exists in the form of peptides in the blood after gastrointestinal digestion. Small peptides containing hydroxyproline can be absorbed intact at the intestinal epithelial cell membrane and reach a high level in the plasma, indicating high absorption rate and bioavailability, and stable and potential biological activity. In this experiment, 15 small peptides containing hydroxyproline were evaluated for their antioxidant activities in vitro by 1,1-diphenyl-2-trinitrophenylhydrazyl (DPPH), 2,2’-azino-bis-(3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) cation, superoxide anion and hydroxyl radical scavenging assays. The results showed that among the small peptides, Leu-Hyp had the highest DPPH radical scavenging activity (23.6%). Leu-Hyp and Ile-Hyp exhibited the highest ABTS cation radical scavenging rates, 57.8% and 57.7%, respectively. The DPPH and ABTS cation radical scavenging capacity of the other small peptides were weak, with scavenging rates less than 15% or 0 for ABTS cation radical scavenging capacity. At a concentration of 3 mmol/L, the hydroxyl radical and superoxide anion radical scavenging capacity of all small peptides were stronger, 30%-50% and 60%-80%, respectively. Collectively, the above results demonstrated that the 15 hydroxyproline-containing peptides had scavenging capacity for hydroxyl and superoxide anion radicals, and that Leu-Hyp and Ile-Hyp had the best antioxidant activity in vitro.

Key words: collagen; hydroxyproline peptide; free radical; antioxidant