Figure 1.

(A) Chemical structures of glycine-proline-hydroxyproline tripeptide (GPH), retinoic acid (RA), and N-acetyl-D-glucosamine (NAG) and the HPLC spectra (B) and contents (C) for total collagen tripeptides and GPH obtained from Pangasius hypophthalmus fish skin hydrolysates (fsCH), by using SuperdexT^TM Peptide 10/300GL column and Zorbax SB-AQ column. The peaks of collagen tripeptides and GPH were identified by the ultraviolet contour plot obtained by a photodiode-array detector at the wavelengths of 214 and 220 nm.