Preparation, typical structural characteristics and relieving effects on osteoarthritis of squid cartilage type II collagen peptides.

[Display omitted] • The preparation of squid cartilage type II collagen peptides (SCIIP) was studied. • SCIIP had typical collagen characteristics with 87.7 % of it below 5 kDa. • SCIIP may inhibit TLR4/MD-2 activation as predicted by molecular docking. • SCIIP alleviated the inflammation in cells by inhibiting the TLR4/NF-κB pathway. • Oral SCIIP relieved the pathological changes of osteoarthritis in rats. The promoting effects of collagen and its derivatives on bone health have been uncovered. However, the structure and effects of type II collagen peptides from squid cartilage (SCIIP) on osteoarthritis still need to be clarified. In this study, SCIIP was prepared from squid throat cartilage with pretreatment by 0.2 mol/L NaOH at a liquid–solid ratio of 10:1 for 18 h and hydrolyzation using alkaline protease and flavourzyme at 50 °C for 4 h. The structure of SCIIP was characterized as a molecular weight lower than 5 kDa (accounting for 87.7 %), a high glycine level of 35.0 %, typical FTIR and CD features of collagen peptides, and a repetitive sequence of Gly–X–Y. GP(Hyp)GPD and GPAGP(Hyp)GD were separated and identified from SCIIP, and their binding energies with TLR4/MD-2 were − 8.4 and − 8.0 kcal/mol, respectively. SCIIP effectively inhibited NO production in RAW264.7 macrophages and alleviated osteoarthritis in rats through the TLR4/NF-κB pathway. Therefore, SCIIP exhibited the potential for application as an anti-osteoarthritis supplement. [ABSTRACT FROM AUTHOR]