Functional soluble dietary fiber from ginseng residue: Polysaccharide characterization, structure, antioxidant, and enzyme inhibitory activity

Ginseng (Panax ginsengC.A. Meyer) is the most famous edible Chinese herbal medicine. In the present study, soluble dietary fiber of ginseng (ginseng-SDF, 8.98% content) was extracted from ginseng residue, and its physicochemical characterization, structure, and biological activities were studied. Ginseng-SDF was an acidic heteropolysaccharide (uronic acid, 4.42% content) rich in protein, amino acids, and mineral elements. Glucose was its main monosaccharide composition (58.03%). Ginseng-SDF had a porous microstructure, a typical cellulose I structure and a large number of hydroxyl functional groups. These chemical composition and structural characteristics gave ginseng-SDF a good water solubility (98.56%), oil-holding capacity (OHC) (3.01 g/g), and biological activities, as the antioxidant activity (13.35 mu M TE/g, 105.17 mu M TE/g, 54.20 mu M TE/g for DPPH, ABTs, and FRAP assays, respectively), glucose diffusion retardation index (GDRI, 33.33%-7.43%), and alpha-amylase/alpha-glucosidase inhibitory activities (IC50, 6.70 mg/ml, and 4.89 mg/ml, respectively). The results suggested that ginseng residue is a valuable source of functional dietary fiber, and the ginseng-SDF has a potential use in antioxidant and hypoglycemic foods. Practical applications Ginseng has long been popular as a health food in Asia, North America, and Europe. Ginseng residue is rich in polysaccharides, dietary fiber, proteins, and other components, which is also of great research value. However, there are few studies focus on the soluble dietary fiber of ginseng at present. The research shows that ginseng residue is a valuable source of functional dietary fiber. The chemical components and structural characteristics give ginseng-SDF a noteworthy antioxidant activity and enzyme inhibitory activity in vitro. These properties and biological activities indicate that ginseng-SDF has application value in antioxidant and hypoglycemic foods.