Preparation of chondroitin sulfates with different molecular weights from bovine nasal cartilage and their antioxidant activities.

Biological functions of chondroitin sulfate, including anti-oxidation and anti-inflammation, are associated with its molecular weight. This study aimed to evaluate the correlation between antioxidant activity and molecular weights of chondroitin sulfate derived from bovine nasal cartilage (BCS). BCS extracted by compound enzymatic method was further purified via DEAE-cellulose column separation to obtain BCS-II (129.4 kDa), which was further degraded by HO-Vc to obtain four subfractions: BCS-II-1 (92.7 kDa), BCS-II-2 (54.1 kDa), BCS-II-3 (26.3 kDa), and BCS-II-4 (19.7 kDa). Changes in the physicochemical properties of BCS-II before and after degradation were compared via FT-IR, NMR and monosaccharide composition analysis. Finally, antioxidant activities of BCS-II and its subfractions BCS-II-1-4 were compared. Our results showed that the HO-Vc system did not disrupt the primary functional group of BCS-II, with no significant change in sulfate content between BCS-II and its degraded fractions; however, uronic acid levels increased in degraded fractions when compared with BCS-II. In vitro, BCS-II-4 displayed the lowest molecular weight and had the strongest antioxidant activity. Therefore, the antioxidant activity of chondroitin sulfate in vitro is robustly associated with its molecular weight, and low-molecular-weight chondroitin sulfate can be used as an antioxidant in the food and pharmaceutical industries and other sectors.