Structural characterization and anti-oxidative activity for a glycopeptide from Ganoderma lucidum fruiting body

Abstract

A water-soluble glycopeptide (named GL-PWQ₃) with a molecular weight (M_w) of 2.40 × 10⁴ g/mol was isolated from Ganoderma lucidum fruiting body by hot water extraction, membrane ultrafiltration, and gel column chromatography, which mainly consisted of glucose and galactose. Based on the methylation, FT-IR, 1D, and 2D NMR analysis, the polysaccharide portion of GL-PWQ₃ was identified as a glucogalactan, which was comprised of unsubstituted (1,6-α-Galp, 1,6-β-Glcp, 1,4-β-Glcp) and monosubstituted (1,2,6-α-Galp and 1,3,6-β-Glcp) in the backbone and possible branches that at the O-3 position of 1,3-Glcp and T-Glcp, and the O-2 position of T-Fucp, T-Manp or T-Glcp. The chain conformational study by SEC-MALLS-RI and AFM revealed that GL-PWQ₃ was identified as a highly branched polysaccharide with a polydispersity index of 1.25, and might have compact sphere structures caused by stacked multiple chains. Moreover, the GL-PWQ₃ shows strong anti-oxidative activity in NRK-52E cells. This study provides a theoretical basis for further elucidating the structure-functionality relationships of GL-PWQ₃ and its potential application as a natural antioxidant in pharmacotherapy as well as functional food additives.

Keywords: Anti-oxidant activity; Ganoderma lucidum glycopeptide; Physicochemical property; Structural characterization.