Preparation,Structural Characterization,Physicochemical Properties And Biological Activities Of Oligosaccharides From American Ginseng

In this study,the enzymatic hydrolysis of American ginseng polysaccharides（AGP）,com-bined with thin-layer chromatography to optimize the hydrolysis conditions.American ginseng oligosaccharides（AGOS）were obtained by ultrafiltration method and characterized by GPC,HPLC,NMR,and FT-IR.The antioxidant activity,in vitro hypoglycemic activity,in vitro lipid-lowering activity,and prebiotic activity of AGOS were evaluated and the results were as follows:The optimal conditions for cellulase enzymatic hydrolysis of American ginseng polysaccha-rides were as follows:enzyme dosage of 100 U/mg,reaction temperature of 45°C,substrate con-centration of 20 mg/m L,and enzymatic digestion time of 90 minutes.The average polymerization of the enzymatic products under this condition was 2.74.The ultrafiltration results showed that AGOS could be prepared by collecting the filtrate of 500 Da-2 k Da ultrafiltration membrane,and the average polymerization degree was 5.34.The results of solubility showed that AGOS had better solubility.The results of rheological properties show that AGOS has low apparent viscosity,which increases the fluidity of AGOS.The results of emulsifying property and emulsifying sta-bility showed that AGOS had lower emulsifying property and emulsifying stability because of its lower molecular weight.The results of foaming property and foaming stability were AGOS<AGP.The molecular weight of AGOS was 1361 Da and its distribution was uniform.The results of monosaccharide composition showed that the monosaccharide composition of AGOS was mainly composed of three monosaccharides,with the molar ratio of mannose:glucose:galactose=1.5:95.2:3.3.The results of NMR and FT-IR showed that AGOS is mainlyα-D-glucopyra-nosylated glucans linked byα-glycosidic bonds.The results of UV absorption spectroscopy indi-cated that AGOS did not contain protein and nucleic acid.The scanning electron microscope re-sults show that the AGOS particles are large and loosely arranged in a network consisting of irregular,uneven,and varied shapes,but filled with particles.XRD results showed that the mo-lecular weight of AGOS decreased and the degree of polymerization decreased.Compared to AGP,AGOS showed stronger antioxidant capacity by measuring the scaveng-ing ability of ABTS⁺,DPPH,OH^-and O^2-free radicals,Fe²⁺chelating ability,and total reducing power.By measuring the ability of AGOS to inhibitα-amylase andα-glucosidase,the results indicated that AGOS had the better hypoglycemic ability.By measuring the ability to bind cholesterol and sodium cholate,as well as the ability to inhibit lipase,AGOS showed a stronger hypolipidemic ability.The effects of AGOS as the sole carbon source on the growth characteris-tics of L.fermentum,L.yohimbe and L.plantarum were investigated,and the viable bacterial counts,bacterial growth curves,changes in p H of fermentation systems,tolerance to the simulated gastrointestinal fluid environment,and short-chain fatty acid accumulation were measured.The results showed that compared with AGP medium,the growth characteristics of AGOS medium with AGOS as the only carbon source were improved compared with AGP medium.AGOS me-dium improves the tolerance and acid production capacity of bacteria in environments that mimic gastrointestinal fluids.It has also been confirmed that AGOS can act as a long-term biotic and promote the production of short-chain fatty acids.