Microwave-Assisted Extraction and Antioxidant Activity of Chondroitin Sulfate from the Cartilage of Dasyatis akajei

The optimal conditions of microwave-assisted extraction (MAE) and papain hydrolysis processes were explored by using single-factor experiments and orthogonal array design with the extraction ratio and purity of polysaccharides as indexes. Under the optimal extraction conditions of microwave power 500 W, sodium hydroxide concentration 12 %, irradiation time 5 min, and solvent to material ratio 40 ml/g, the yield of glycosaminoglycans (GAGs) from the cartilage of D. akajei was 13.87 ± 0.64 %. The optimum conditions of enzymatic hydrolysis was temperature 45°C, pH 6.8, time 4 h and enzyme amount 1.0 %. Under the optimal condition, the purity of polysaccharide reached to 89.57 % ± 2.17 %. The antioxidant activities tests indicated both the GAGs and chondroitin sulfate had noticeable effects on scavenging free radicals, especially at high addition quantity. The results suggest that the polysaccharide purified from the cartilage of D. akajei has good potential as a natural antioxidant used in food and/or medicine industries.