The structure and antioxidant activities of three high molecular weight polysaccharides purified from the bulbs of Lanzhou lily

With hot water extraction and ethanol precipitation, three high molecular weight polysaccharides, LZLs (LZL-1, LZL-2 and LZL-3), were successfully purified from the edible bulbs of Lanzhou lily by DEAE-52 cellulose and sephadex G-200 column. The structure features of LZLs were characterized by gas chromatography, scanning electron microscope, high performance gel-permeation chromatography, IR and NMR, and the antioxidant activities of LZLs were assayed. The results showed that LZL-1, LZL-2 and LZL-3 were composed of glucose and mannose with the molar ratios of 2.4:2.5, 2.6:2.5 and 2.2:2.5, while their molecular weights were 2.33 x 10(6), 1.92 x 10(6) and 1.26 x 10(6), respectively. LZLs were mainly alpha-pyranose configurations with lamellar structure and triple helix conformation except LZL-3. LZLs had similar glycosidic linkage patterns with main substitution at O-6 of glucose or mannose but the different substitution positions at O-3 of them. Vitro bioassays showed that LZLs had effective scavenging abilities to free radicals, especially to DPPH and hydroxyl radicals. When the concentration reached 4 mg/mL, the scavenging rate of LZLs to DPPH and hydroxyl radicals were up to 60% and 70%, respectively. These findings provided more references for potential applications of Lanzhou lily polysaccharides as natural antioxidant agents in food and pharmaceuticals.