Generation of cyclic peptides with improved anti-Photoaging activity during the thermal processing of collagen peptides.

This study explored the structural changes of collagen peptides during heat treatment under different conditions that might affect their anti-photoaging activities. Results showed that the matrix metalloproteinase-1 (MMP-1) inhibition rate of collagen hydrolysates significantly increased after heat treatment at various pH values, and its contents of Hyp (O)-containing and Gly-Pro-Xaa tripeptides significantly reduced, while cyclic dipeptides such as cyclo(LO), cyclo(FO), and cyclo(GP) were formed. Specifically, cyclo(LO) and cyclo(GP) displayed stronger MMP-1 inhibition (64.12% and 52.81%, respectively) than the linear di- and tripeptides LO, LOG, GPI and GPM (35.86%, 22.03%, 21.28% and 41.14%, respectively). This might be due to their increased conformational rigidity and strengthened hydrophobic interactions with MMP-1. Additionally, the cyclic dipeptides cyclo(PO), cyclo(LO), cyclo(AO), cyclo(SO), cyclo(FO) and cyclo(GP) significantly enhanced the viability of fibroblasts damaged by UVA. The results highlighted the cyclic form of Hyp-containing dipeptides with improved anti-photoaging activity generated upon heat treatment and its potential application in skin health.