Structure, Chemical Modification And Bioactivities Of An Novel Expolysaccharide From Lachnum

In the present study, the extracellular homogeneous polysaccharide (LEP-2a) from Lachnum YM406 was prepared through fermentation, extraction and purification. The primary structure of LEP-2a was characterized by methylation analysis and nuclear magnetic resonance (NMR), while its antioxidant and reducing blood glucose activities were evaluated. Moreover, the phosphorylation and selenylation of LEP-2a were prepared, respectively, and the hepatoprotective effects of LEP-2a on CCl4-induced acute liver injury model mice before and after modifications were studied.Structure analysis results showed that LEP-2a was one homogeneous galactomannan with relative molecular weight of 2.3×104 Da and its relative mole ratio of mannose (Man) to galactose (Gal) was 95.05:4.95. Its backbone was consisted of a-(1?3,4)-D-Manp, a-(1?2)-D-Manp, a-(1?2,6)-D-Manp and ?-(1?3)-D-Galp, while side chains were consisted of ?-D-Manp-(1?, a-(1?3,4)-D-Manp, a-(1?2)-D-Manp, ?-(1?2,6)-D-Manp and ?-(1?3)-D-Galp. Antioxidant and reducing blood glucose experiments showed that LEP-2a could effectively scavenge hydroxyl radicals and superoxide anion, suppress lipid peroxidation, inhibit a-glucosidase activity and reduce blood glucose in mice.Phosphorylation and selenylation modifications of LEP-2a were conducted to obtain PLEP-2a and SeLEP-2a, respectively. Characteristic absorption peaks of phosphate ester at 530 cm-1,1060 cm-1 and 1260 cm-1 were appeared in FT-IR spectrum of PLEP-2a, while characteristic absorption peaks of selenite ester at 673 cm-1 and 893 cm-1 were appeared in FT-IR spectrum of SeLEP-2a, which indicated that phosphorylation and selenylation modifications were successful.13C NMR spectra analysis results showed that phosphate group substituted at C-2 and C-4 of a-D-Manp-(1? C-2 of a-(1?3,4)-D-Manp, C-4 of a-(1?2)-D-Manp or a-(1?2,6)-D-Manp and C-6 of Man or Gal, while selenite group substituted at C-2 of a-D-Manp-(1? and C-6 of Man or Gal.To evaluate hepatoprotective effects of LEP-2a, PLEP-2a and SeLEP-2a, acute liver injury models were established by intraperitoneal injection of CCl4. The experimental results showed that LEP-2a, PLEP-2a and SeLEP-2a had hepatoprotective effects on CCl4-induced liver injury in mice with dose-effect relationships.Hepatoprotective effects of PLEP-2a and SeLEP-2a were more significant than same dose of LEP-2a, which indicated that phosphorylation and selenylation could improve hepatoprotective activities of LEP-2a. Compared with model group, hepatosomatic indexes and serum hepatotoxicity indexes were decreased, while activities of antioxidases and contents of glutathione (GSH) in liver were increased and levels of malonaldehyde (MDA), cytochrome P4502E1 (CYP2E1), nuclear factor ?B (NF-?B), interleukins 1? (IL-1?) and interleukin 6 (IL-6) in liver tissues were decreased in PLEP-2a and SeLEP-2a groups. Moreover, histopathological observation experiment displayed that structures of hepatic cells were improved and contents of fat droplets were decreased in mice of PLEP-2a and SeLEP-2a groups. The possible mechanisms of the hepatoprotective effects of LEP-2a and its derivates may be related to development of antioxidant defense system, inhibition of inflammatory reaction and promotion of regeneration of the damaged liver tissue.