Molecular properties, structure, and antioxidant activities of the oligosaccharide Hep-2 isolated from cultured mycelium of Hericium erinaceus

The oligosaccharide Hep-2 from cultured mycelium of Hericium erinaceus was obtained with a hollow-fiber ultrafiltration cartridge and purified with a DEAE Sephadex A-50 column followed by a Bio-Gel P-30 column. The properties, structure, and antioxidant activities of Hep-2 were studied. Hep-2 had the molecular weight of 1,080 Da and consists of Glc and Gal in a molar ratio of 1.0:0.4. Fragmentation analysis by GC-MS suggests that the structure of Hep-2 consists of three linear sugar residues. Furthermore, we used the LC-MSn combined methylation method to determine the types of bonds between sugar residues. We found that the structure of Hep-2 is based on 2-7 sugars. Among these, the trisaccharides and pentasaccharides consist of 1 -> 6-Gal, whereas the tetrasaccharides, hexasaccharides, and heptasaccharides consist of 1 -> 4-Glc and 1 -> 6-Gal. The activity tests indicated that Hep-2 significantly reduced the damage caused by H2O2 in GES-1 cells, and could induce expression of T-SOD and GSH-px, scavengers of oxygen free radicals, in a concentration-response manner. Hep-2 also reduced cell apoptosis as assessed by changes in the ratio of Bcl-2/Bax proteins by western blot. Both sets of results suggest that Hep-2 might possess significant antioxidant activity. Practical applications This paper reports the physical and the chemical parameters, structure and biological potential of oligosaccharides from Hericium erinaceus, a common edible fungus. Hericium erinaceus has been used as an anti-atrophic gastritis drug in China with good effect. Oligosaccharides are more easily digested and utilized by human body, and have strong antioxidant activity. These results can increase people's interest in the product, and thus have a positive impact on the oligosaccharides of Hericium erinaceus as health food.