Structural Characterization and Biological Evaluation of a Novel GlcNAc-Bearing Exopolysaccharide from the Mangrove Endophytic Fungus Penicillium janthinellum N29

A novel, uniform acid heteropolysaccharide with a molecular weight of 13.14 kDa was isolated from the fermented broth of the mangrove endophytic fungus Penicillium janthinellum N29, designated as PJ3-1. A structural analysis showed that PJ3-1 is a straight-chain heteropolysaccharide containing GlcN, GlcNAc, Glc and GlcA in the ratio of 12.23:1.79:10.93:1.00. PJ3-1 markedly inhibits α-glucosidase activity and relieves insulin resistance in HepG2 cells. It alleviates lipid peroxidation and upregulates the activities of endogenous antioxidant enzymes. In addition, it also significantly scavenges hydroxyl radicals, ferrous ions, superoxide anions, DPPH radicals and ABTS radicals and enhances reducing power in a dose-dependent manner. Collectively, these findings suggest that PJ3-1 has the potential to serve as a natural antioxidant and hypoglycemic agent for functional food or pharmaceutical applications.