Chicken keel cartilage as a source of chondroitin sulfate

Chondroitin sulfate is used extensively as a treatment for osteoarthritis. This study was conducted to evaluate whether chondroitin sulfate could be isolated from chicken keel cartilage in sufficient quantities and of requisite quality to make it a feasible source of chondroitin sulfate. Proteoglycans were extracted from chicken keel cartilage obtained immediately after slaughter by using 3 M MgCl2 at room temperature. The extract was then dialyzed and digested with papain to remove proteins. Glycosaminoglycans were obtained by ethanol precipitation, lyophilized, and characterized by using gel filtration on Sepharose CL-6B columns. Guanidine-HCI extraction was also used as a control to investigate the efficiency of extraction using MgCl2. Results showed that, from every gram of wet or non-lyophilized keel cartilage, 32.9 +/- 4.8 mg (dry weight) of glycosaminoglycans could be obtained following MgCl2 extraction. Analyses revealed that 75.5 +/- 4.2% of these glycosaminoglycans were chondroitin sulfate. Chromatographic analyses showed a single symmetrical peak, which could be almost entirely removed by prior digestion with chondroitinase ABC, indicating that the material in the peak was in fact chondroitin sulfate. The average molecular weight (also called relative molecular mass, Mr) of the glycosaminoglycans was also estimated (Mr 48,500). Characterization using polyacrylamide or agarose gel electrophoresis showed diffuse bands containing chondroitin sulfate, which could be entirely removed by prior digestion with chondroitinase ABC. This study shows that chicken keel cartilage is a readily available source of chondroitin sulfate.