Structure and preventive effects against ethanol-induced gastric ulcer of an expolysaccharide from Lachnum sp.

• An extracellular polysaccharide of Lachnum sp. (LEP) was isolated and purified.
• LEP-2a was a (1→3)-,(1→6)-β-D-Glcp.
• The branch chain was consist of two d-glucopyranosyl residues linked by β-1,3-glycosidic linkage.
• The branch chain was linked at C6 of the backbone chain by β-1,6-glycosidic linkage.
• LEP-2a had a significant preventive effect against the ethanol-induced gastric ulcer.

An extracellular polysaccharide of Lachnum sp. (LEP) was purified by DEAE-cellulose 52 column chromatography and Sepharose CL-6B column chromatography. LEP-2a was identified to be a homogeneous component with an average molecular weight of 3.22 × 104 Da. The structure of LEP-2a was characterized by chemical and spectroscopic methods, including methylation analysis, periodate oxidation-smith degradation, infrared spectroscopy and NMR analysis. Results indicated that LEP-2a was a (1→3)-,(1→6)-β-D-Glcp, whose branch chain was consist of two d-glucopyranosyl residues linked by β-1,3-glycosidic linkage, which was linked at C6 of the backbone chain by β-1,6-glycosidic linkage. To study the protective effects of LEP-2a on the ethanol-induced gastric ulcer in mice, LEP-2a (100, 200 and 400 mg/kg/d) was given to mice by gavage for 2 weeks. Results showed that LEP-2a significantly decreased the ulcer bleeding areas, pepsin activity, gastric juice volume, gastric juice total acidity and the malondialdehyde (MDA) content in serum. Meanwhile, the superoxide dismutase (SOD) increased significantly. The above findings suggested that LEP-2a had a significant preventive effect against the ethanol-induced gastric ulcer.