Colloidal Behavior Of Polysaccharides And Structure And Activities Of The Selenide Polysaccharides From Lignosus Rhinocerotis Under Ultrasound

Lignosus rhinocerotis,an edible and medicinal fungi,and polysaccharides are one of the most important components.Previous studies found that the Lignosus rhinocerotis polysaccharides（LRP）could be changed from solution to micelle.Therefore,the solution gelation behavior of LRP was further studied by fluorescent pyrene probe and atomic force microscopy,and the effect of ultrasound on the sol-gel transition and molecular morphology of LRP solution.Furthermore the polysaccharide was modified by selenium（LRP-SeNPs）under ultrasound,the mechanism of ultrasound not only on the structure and stability but also the antioxidant activity and non-enzymatic glycation inhibition of LRP-SeNPs was investigated.This paper explored the mechanism of ultrasound on macromolecular aggregate structure,promoting the development of LRP and LRP-SeNPs as food and health care products.The results were as follows:1.From the fluorescent pyrene probe,LRP changed from solution to micelle as the concentration increased,and the system has a critical association concentration point（CAC）.The CAC of gel formation in LRP aqueous solution at 25℃was detected by different ultrasonic time（0,1,10 and 60 min）.It was found that with the prolongation of ultrasonic time（0-10min）,LRP solution CAC would decreased（2.5→1.8 mg/ml）,which means accelerating gel formation,however,when the ultrasonic time was 60 min,floc was generated in LRP aqueous solution.Then,different temperature（4 and 25°C）was further studied.It is found that the CAC will be increased at 4℃,which means inhibiting gel formation,the results showed that the stability of LRP was better at 4℃,and the gel forming at 25℃was more suitable,the LRP solution with ultrasound for 10 min at 25°C could form micelles at a lower concentration（1.8 mg/mL）than with no ultrasound.2.The LRP molecular morphology with different ultrasonic time（0,1,10 and 60min）was observed by atomic force microscope（AFM）at 25℃.The original LRP molecular morphology without ultrasound were dominated by spherical aggregates,which led to the increase of steric hindrance and reduce the formation of hydrophobic microdomains,pyrene were difficult to enter the hydrophobic microregion,resulting the higher I₁/I₃ and fall slower.With the prolongation of ultrasound time,the LRP will be untangled to varying degrees and become individual branch chains,these individual branches will be further recombined and entangled and become a stable network structure,ultrasound reduced the steric hindrance,promoted the association of the LRP hydrophobic microregion and increased the dissolution of pyrene,the I₁/I₃decreases rapidly,CAC value decreases to 1.8 mg/mL.When the ultrasonic time was further extended,the network structure will be destroyed and entangled to form spherical or irregular aggregates.The results show that ultrasound 10 min LRP molecular morphology was a network structure with good stability.3.From AFM,the molecular morphology of LRP in DMSO and 0.25 mol/L DMSO/LiCl was sphere and the particle size is about 20-40 nm.Compared with the aqueous solution,LRP had a smaller particle size and more uniform distribution in the DMSO and DMSO/LiCl system,demonstrating the DMSO and DMSO/LiCl system was a better solvent for LRP.4.The differences between ultrasonic and non-ultrasonic approaches in synthesizing LRP-SeNPs were compared in terms of size,morphology,stability by UV-VIS,FT-IR,XRD,DLS,TEM,EDX and TEM.Results indicated that the SeNPs were associated with the LRP macromolecules in a physical adsorption pattern without breakingchemical bonds,and the ultrasonic treatment reduced the size of SeNPs,narrowed the size distribution as well as improved the stability.Due to the LRP compact coil structure loosed under ultrasonic cavitation,the SeNPs could be easily diffused into the LRP internal branches instead of gathering on the LRP surface and were well dispersedand eventually stabilized throughout the extended branches.After ultrasound treatment,the SeNPs had a minimum average diameter of～50 nm and the LRP-SeNPs could remain homogeneous and translucent for 16 days within200 nm size.The integrated results demonstratedthat ultrasound played a crucial role in the dispersion,size control,stabilization of SeNPs.5.The inhibitory effects of LRP-SeNPs on antioxidant activities,non-enzymatic glycation were studied.The relationship between structure and activity and the role of ultrasound were discussed.The results showed that LRP-SeNPs scavenge ABTS and DPPH free radicals better than single LRP,and ultrasound treatment could significantly improve the scavenging capacity of ABTS and DPPH free radicals,the inhibition rates of ABTS and DPPH free radicals by Se/LRP=1/10 were 52.24%,22.09%,respectively,after ultrasonic treatment were 83.18%,52.31%,respectively.This difference may be attributed to the reason that ultrasound can reduce the SeNPs size and increase the specific surface area,which provides sufficient active sites to react with the free radicals and suppress the oxidizing reactions.The inhibitory effect of U-LRP-SeNPs on the non-enzymatic glycation was studied from three different stages by Fluorescence Spectrometer and SDS-PAGEs.0.6 mg/mL U-LRP-SeNPs had good inhibitory effects on the formation of dicarbonyl compounds,the inhibition rates of Se/LRP=1/15 and 1/10 were 50%and 46%.And U-LRP-SeNPs can effectively inhibit the formation of AGEs,the inhibitions rate of Se/LRP=1/15 and 1/10 were about 20%and 30%.Furthermore,the SDS-PAGE result was consistent with the fluorescence spectrometer one.