Chemical structure and antioxidant activity of the biomacromolecules from paddlefish cartilage

To evaluate the effect of extraction methods on chemical structure and association with antioxidant activity of the extracts from paddlefish cartilage, the three extracts (EXT-A, EXT-B and EXT-C) were obtained from the cartilage by signal alkali extraction, microwave-assisted alkali extraction, and microwave-assisted alkali extraction followed by Sevag's deproteinization, respectively. Chemical structures of the polymer were investigated by GPC (Gel Permeation Chromatography), FT-IR, GC and amino acid analysis. The results indicated that both EXT-A and EXT-B consisted of polysaccharide and protein, but the protein content of EXT-B (87.9%) was significantly higher than EXT-A (22.3%). Meanwhile EXT-C was polysaccharide composed of glucose, galactose, c-glucuronic acid and xylose. EXT-B extracted by microwave-assisted alkali method, containing dominant protein and rich in tyrosine, glycine and glutamic acid, exhibited obviously higher antioxidant activity than those of the extracts by other methods. The results indicated that microwave-assisted alkali extraction was favorable for protein dissolving out of cartilage, and protein content and composition of the extracts play important roles in antioxidant activity. (C) 2012 Elsevier B.V. All rights reserved.