Antioxidant activities of polysaccharide fractions isolated from burley tobacco flowers

The crude polysaccharide extracted from the flowers of burley tobacco hybrid Eyan 1 was fractionated on a Sepharose CL-6B chromatography to get two purified polysaccharide fractions (termed Fr-I and Fr-II). The monocarbohydrate compositions revealed both fractions were heteropolysaccharide. Fr-I was mainly composed of mannose, galactose, ribose and arabinose, while Fr-II was composed of mannose, galactose and glucose. The IR spectrum of Fr-I and Fr-II revealed the typical characteristics with β-configuration. Furthermore, TGA (Thermogravimetric analysis) indicated the degradation temperature (Td) of the Fr-I and Fr-II was 210 °C and 185 °C, respectively. Both Fr-I and Fr-II possessed good scavenging abilities on hydroxyl radicals (IC50 8.26 mg/ml and 6.23 mg/ml, respectively) and DPPH radicals (IC50 20.3±1.20 μg/ml, 17.5±1.28 μg/ml, respectively). Fr-II showed higher antioxidant properties than Fr-I (p < 0.05). In a 13 C NMR analysis of Fr-II, three anomeric peaks appeared at 102.95, 95.79 and 91.85 ppm, which were assigned to the mannose (C-1), galactose (C-1) and glucose (C-1) residues, respectively.