Physicochemical properties, structure, growth-promoting and antioxidant activities of Glycyrrhiza leaf polysaccharides modified by fermentation

This study aimed to investigate the effects of fermentation on the physicochemical properties and in vitro antioxidant activities of Glycyrrhiza leaf, compare the structures of unfermented (GLP) and fermented (FGLP) polysaccharides, and assess their growth-promoting and antioxidant activities using zebrafish embryos. The results showed that the polysaccharide content, extract yield, and reduced sugar content of Glycyrrhiza leaf increased significantly after 36 h of fermentation. In parallel, in vitro antioxidant activities assays demonstrated that Glycyrrhiza leaf fermented for 36 h exhibited strong DPPH, hydroxyl radical scavenging, and reducing power. Scanning electron microscope and infrared spectroscopy analyses revealed differences in the surface morphology of unfermented and fermented Glycyrrhiza leaf, with both polysaccharides being acidic and containing pyranose rings and α-glycosidic bonds. The molecular weight of FGLP was lower than that of GLP, and the molar ratios of guluronic acid, amino glucose, glucuronic acid, glucose, xylose, and arabinose were increased. In the zebrafish model, Glycyrrhiza leaf polysaccharides promoted the growth and development of zebrafish embryos, with the most pronounced effect at a concentration of 20 µg/mL after fermentation. FGLP exhibited superior protective effects against lipid peroxidation and cell death induced by 2,2′-azobis (2-methylpropionamidine) dihydrochloride. The findings demonstrated that fermentation could enhance the utilization of Glycyrrhiza leaf polysaccharides and their antioxidant capacity. These findings opened avenues for further research into the bioavailability of FGLP in vivo and offered valuable insights into its potential as a natural and innovative antioxidant. Highlights