Conjugate between hydrolyzed collagen from defatted seabass skin and epigallocatechin gallate (EGCG): characteristics, antioxidant activity and in vitro cellular bioactivity

Conjugation between peptides and polyphenols, especially epigallocatechin gallate (EGCG) using covalent grafting, is a promising method that can modify peptides or augment their antioxidant activities. Moreover, the resulting conjugates can be intensively served as functional ingredient or supplement. Thus, the objectives of the present study were to investigate the grafting between hydrolyzed collagen (HC) from defatted seabass skin and EGCG and to study characteristics as well as bioactivities of the obtained HC-EGCG conjugate. Levels of EGCG used (1-5%, w/w) affected surface hydrophobicity (SH) and antioxidant activities of the conjugates. Overall, the addition of EGCG at 3% to HC (HC-3% EGCG) increased SH, ABTS radical scavenging and metal chelating activities (p < 0.05). FTIR spectra of HC-3% EGCG revealed the interaction between HC and EGCG via H-bonding and covalent interaction. Sephadex G-25 fraction of conjugate with molecular weight (MW) of 2771 Da rendered the highest redox ability. When HC-3% EGCG was applied in fibroblast (MRC-5) and keratinocyte (HaCaT) cells, all levels tested (125-1000 μg mL-1) had no toxicity on both cells. Higher proliferation of both cells were attained with increasing levels of HC-3% EGCG, particularly at 500 and 1000 μg mL-1 (p < 0.05). Moreover, both levels used had cytoprotective ability against reactive oxygen species (ROS) as evidenced by lowered ROS and cell death detected as compared to those found in cells induced with H2O2 or AAPH alone (p < 0.05) for both cells. HC-3% EGCG could serve as an effective antioxidant for application in foods or as supplement for skin nourishment.