Chemical structure and antioxidant activity of the biomacromolecules from paddlefish cartilage

► EXT-A B and C were extracted by alkali, microwave-assisted alkali and Sevag method. ► EXT-A and B consisted of polysaccharide and protein while EXT-C was polysaccharide. ► The protein content of EXT-B was significantly higher than EXT-A and EXT-C. ► Microwave-assisted alkali method was favorable for protein extraction. ► The main contributor to antioxidant activity was protein rather than polysaccharide.