Antioxidant Activity of Water-soluble Polysaccharides from Brasenia schreberi

OBJECTIVE: In order to investigate the antioxidant activities of polysaccharides (BPL-1 and BPL-2), one of the most important functional constituents in Brasenia schreberi was isolated from the external mucilage of B. schreberi (BPL-1) and the plant in vivo (BPL-2). This paper examines the relationship between the content of sulfuric radicals and uronic acid in BPL and the antioxidant activity of BPL. MATERIALS AND METHODS: The free radicals, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) and 1,1-diphnyl-2-picrylhydrazyl (DPPH-), were used to determine the antioxidant activity of BPL. The Fourier-transform infrared spectroscopy of BPL-1 and BPL-2 revealed typical characteristics of polysaccharides. RESULTS: The two sample types had different contents. This was proved by their different adsorption peak intensities. The IC50 values of BPL-1 (31.189 mg/ml) and BPL-2 (1.863 mg/ml) showed significant DPPH radical scavenging activity. Based on the quantification of ABTS radical scavenging, the IC50 value of BPL-1 (5.460 mg/ml) was higher than that of BPL-2 (0.239 mg/ml). Therefore, in terms of the reducing power, the IC50 value of BPL-1 was too high to determine, and the IC50 value of BPL-2 was found to be 50.557 mg/ml. Hence, the antioxidant activity and total reducing power were high, and they were greater in BPL-2 than in BPL-1. In addition, BPL-2 was found to have more sulfuric radicals and uronic acid than BPL-1. CONCLUSION: The contents of sulfuric radicals and uronic acid are significantly correlated to the antioxidant activity and reducing power of BPL; the more sulfuric radicals and uronic acid, the more antioxidant activity and reducing power BPL has. SUMMARY: The water-soluble crude polysaccharides obtained from the external mucilage and the Brasenia schreberi plant in vivo were confirmed to have high contents of sulfuric radicals and uronic acid. Both BPL-1 and BPL-2 exhibited antioxidative activity and reducing power, and their antioxidative activity gradually improved with increasing concentrations. The content of sulfuric radicals and uronic acid in BPL-1 and BPL-2 might explain their high antioxidant activity. Abbreviations used: BPL-1:Polysaccharide were isolated from the external mucilage of B. Schreberi; BPL-2: Polysaccharide were isolated from the plant in vivo of B. schreberi; BPL:Polysaccharide were isolated from B. Schreberi.