Purification, characterization and immunomodulatory activity of polysaccharides from stem lettuce.

Stem lettuce has a long history of cultivation in China and possesses high nutritional and medicinal value. In our previous studies, extraction optimization, characterization, and bioactivities of stem lettuce polysaccharides (SLP) were investigated. In this study, SLP were further separated into two purified polysaccharides, SLP-1 and SLP-2, by anion exchange chromatography followed by size exclusion chromatography. SLP-1, with a molecular weight of 90 KDa, was mainly composed of galacturonic acid, galactose and arabinose in a molar ratio of 17.6:41.7:33.9. SLP-2, with a molecular weight of 44 KDa, was mainly composed of mannose, galacturonic acid, galactose and arabinose in a molar ratio of 11.5:69.5:9.3:8.2. In addition, both purified polysaccharides contain sulphate radicals, have triple helical structures and can promote macrophage proliferation without cytotoxicity. SLP-2 was better able to stimulate phagocytic and nitric oxide production than SLP-1. The results suggest that polysaccharides from stem lettuce could be explored as immunomodulatory agents in the field of pharmaceuticals and functional foods.

Characterization, antioxidant activity and immunomodulatory activity of polysaccharides from the swollen culms of Zizania latifolia.

The swollen culms of Zizania latifolia have been used as a vegetable and traditional herbal medicine in China, Japan, Korea and Southeast Asia countries. Up to date, there is little information about the polysaccharides from the swollen culms of Zizania latifolia and their potential bioactivities. In the present study, water extractable polysaccharide (ZLPs-W) and alkali extractable polysaccharide (ZLPs-A) was sequentially prepared from the swollen culms of Zizania latifolia. Both of ZLPs-W and ZLPs-A was found to be non-starch polydisperse heterpolysaccharide with ß-type glycosidic linkage. ZLPs-W with triple helix conformation mainly composed of GalA, Glc and Gal. ZLPs-A without triple helix conformation mainly composed of Glc, Gal, Xyl and Ara. In in vitro antioxidant assay, ZLPs-W and ZLPs-A exhibited good scavenging activities. The EC50 of DPPH radical, superoxide radical and hydroxy radical scavenging activities for ZLPs-A is 1.87, 1.13 and 0.38mg/mL compared with that for ZLPs-W is 2.95, 3.99 and 0.5mg/mL, respectively. Moreover, in vitro cell assay revealed that ZLPs-W without cytotoxicity has higher immunomodulatory activity than ZLPs-A in terms of stimulation of phagocytic ability and NO production in murine macrophage RAW 264.7. At the treated concentration of 400µg/mL and 100µg/mL, ZLPs-W induced a highest phagocytosis index (1.76) and NO product (29.12µmol/L), respectively. The results suggest that polysaccharide from the swollen culms of Zizania latifolia could be explored as potential natural antioxidant and immunomodulatory agents in medicine or functional food fields.

Preliminary characterization, antioxidant activity in vitro and hepatoprotective effect on acute alcohol-induced liver injury in mice of polysaccharides from the peduncles of Hovenia dulcis.

The fresh fleshy peduncles of Hovenia dulcis have been used as a food supplement and traditional herbal medicine for the treatment of liver diseases and alcoholic poisoning for more than a millennium. The objectives of the present study, therefore, were to determine the antioxidant activity of polysaccharides from the peduncles of H. dulcis (HDPS) and to evaluate its hepatoprotective effect on acute alcohol-induced liver injury in mice. HDPS, prepared by hot water extraction, ethanol precipitation and treatment of macroporous resin, was found to be non-starch polysaccharide and mainly composed of galactose, arabinose, rhamnose and galacturonic acid. In in vitro antioxidant assay, HDPS exhibited high superoxide radical scavenging activity, strong inhibition effect on lipid peroxidation and a medium ferrous ion-chelating activity. For hepatoprotective activity in vivo, the administration of HDPS significantly decreased the serum levels of alanine aminotransferase and aspartate aminotransferase, significantly decreased the liver level of malondialdehyde and remarkably restored the liver activities of superoxide dismutase and glutathione peroxidase in alcohol-induced liver injury mice. The results suggested that HDPS had a significant protective effect against acute alcohol-induced liver injury possibly via its antioxidant activity to protect biological systems against the oxidative stress.