Purification, characterization and antioxidant properties of low molecular weight collagenous polypeptide (37 kDa) prepared from whale shark cartilage (Rhincodon typus).

A low molecular weight type-II collagenous polypeptide (CIIp) from whale shark (WS) cartilage was prepared by thermolysin digestion; and examined for their physico-functional and antioxidant properties. The purified collagen was composed of an identical (α1)3 chains and was characterized as type-II. After hydrolysis with thermolysin, the α-chain of the WS collagen was degraded into smaller peptides with molecular weight ranging from 70 to 20KDa. CIIp was successfully separated from the hydrolysates with molecular weight of approximately 37 kDa. Amino acid analysis of CII, and CIIp indicated imino acid contents of 155 and 121 amino acid residues per 1000 residues, respectively. Differing Fourier transform infrared (FTIR) spectra of CII and CIIp were observed, which suggested that the hydrolysis process by thermolysin affected the secondary structure and molecular order of collagen, particularly the triple-helical structure. The denaturation temperature of CII (34 °C) was higher than that of CIIp. Low content of glycoprotein was observed in CII than CIIp due to removal of some polypeptides by thermolysin digestion. The antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl radicals and the reducing power of CIIp was greater than that of CII. The results proposed that the purified CIIp from WS cartilage with excellent antioxidant activities could be the suitable biomaterial for therapeutic applications.