Investigation On The Bioactivities Of Corn Silk Polysaccharides And Their Binding Interaction With Flavonoids From Corn Silk

Corn silk dried cut stigmata of maize(Zea mays L.)female flowers,is a well-known functional food and traditional Chinese herbal medicine.It has been widely used to treat edema,cystitis,gout,nephritis,kidney stones,obesity,as well as prostatitis and similar ailments.It consists of various bioactive components such as cross fiber,polysaccharides,flavonoids,organic acid,saponins,alkaloids and other chemicals,which have significant influences on human health.Previous studies on polysaccharide from corn silk had shown that it possessed beneficial effects such as antioxidant,antitumor,antidiabetic,antifatigue,anti-obesity and it was considered to be a potential functional agent for human consumption.The study aimed at providing a reference for the full utilization of polysaccharides from corn silk.Hypoglycemic effects of polysaccharides from corn silk(CSP)and their beneficial roles via regulating the phosphatidylinositol 3-kinase/protein kinase B(PI3K/Akt)signaling pathway in L6 skeletal muscle myotubes were investigated.Structural characterization of purified corn silk polysaccharides and its effect in H₂O₂induced oxidative damage in L6 skeletal muscle cells were also studied.The binding characteristics of polysaccharides and flavonoids from corn silk were studied by adsorption experiment.Hypolipidemic and hypoglycemic effects of polysaccharides from corn silk were investigated in L6 skeletal muscle cells.Three polysaccharides fractions obtained from corn silk(CSP1,CSP2 and CSP3)were isolated and the physicochemical properties were characterized by gel permeation chromatography(GPC),fourier transform-infrared spectroscopy(FT-IR),scanning electron microscope(SEM)and gas chromatography(GC)methods.Their inhibitory actions against?-glucosidase and?-amylase were evaluated.Their effects on glucose uptake and mechanism of action in PI3K/Akt signaling pathway were also determined in L6 skeletal muscle cells.Results demonstrated that CSP could significantly inhibit activity of?-amylase and?-glucosidase(P<0.05).CSP were non-toxic and they considerably increased the 2-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino-2-deoxy-D-glucose(2-NBDG)uptake(P<0.05)in L6 cells.Additionally,CSP regulated the PI3K/Akt signaling pathway and promoted the translocation of glucose transporter 4(GLUT4)to the plasma membrane that would enhance the glucose uptake in rat L6 skeletal muscle cells.Among the tested polysaccharides,CSP2 with the average molecular weight distribution of 62.16 k Da exerted appreciable hypoglycemic activity.Altogether it was suggested that CSP could be a promising candidate in the treatment of Type 2 Diabetes Mellitus(T2DM).The elucidation of the potential hypoglycemic mechanism of the polysaccharides from corn silk will facilitate their utilization in the functional food industries.Antioxidant activity of polysaccharides from corn silk in H₂O₂ induced oxidative damage was evaluated in L6 skeletal muscle cells.CSP1,CSP2 and CSP3 were each further purified by a DEAE sepharose fast flow column.CSP1-2,CSP2-2 and CSP3-2were obtained.Structure analysis of CSP2-2 with ¹D and ²D NMR indicated that CSP2-2 was composed of(1?6)-linked?-D-glucose.The substituent of the?-D-glucose is composed of(1?3)-linked?-L-arabinose,(1?4)-linked?-D-galactose and(1?3,5)-linked?-D-mannose,with?-D-xylose and?-L-rhamnose as terminal unit.CSP2-2 had the potential to scavenge diphenyl picryl hydrazinyl radical(DPPH)and hydroxyl radical and inhibit hemolysis in vitro.CSP2-2 was found to suppress oxidative stress by improving the enzyme activities of superoxide dismutase(SOD),catalase(CAT),and glutathione peroxidase(GPX).Rodamine 123 staining results showed that the pretreatment of CSP2-2 prevented changes in the mitochondrial membrane potential and increased the fluorescence intensity in L6 cells in the presence of H₂O₂.These results suggested that CSP2-2 could be utilized as a potential antioxidant supplement to prevent oxidative stress.The binding interaction between three corn silk polysaccharide fractions(CSP1-2,CSP2-2 and CSP3-2)and flavonoids(luteolin,apigenin and formononetin)from corn silk was characterized using molecular dynamic and thermodynamic simulation.The corn silk polysaccharides-flavonoids complex(P-F complex)was characterized using FT-IR spectra,circular dichroism(CD),SEM and differential scanning calorimetry(DSC).The three CSP fractions showed the average molecular weight distributions of43.3 k Da,61.3 k Da and 106.6 k Da,respectively,and they had the same monosaccharide types with different ratios.The adsorption of flavonoids to polysaccharides might be mostly driven by van der Waals forces and hydrogen bonding,and it could be described through various isothermal models and thermodynamic equations such as Langmuir,Freundlich equations and Clausius-Clapeyron equation.This type of interactions could improve the biological activities of polysaccharides from corn silk such as?-amylase and?-glucosidase inhibition.In conclusion,corn silk polysaccharides could regulate signaling pathway,promote glucose uptake,enhance the activity of antioxidant-related enzymes.Corn silk polysaccharides showed good antioxidant and hypoglycemic activity.Further study on the activity and mechanism of corn silk polysaccharide will be carried out in the future.The future comprehensive utilization of corn silk will also need more in-depth exploration.