Study On The Preparation,Characterization And Metabolism Of Astilbin-zein Nanoparticles

Astilbin(AST)is a flavonoid widely found in a variety of plants and functional foods.It has a range of healthy and beneficial,such as selective immune function,antioxidant,regulationof fat and cholesterol metabolism,and alleviation of myocardial cell ischemia-reperfusion injury.However,due to the low water solubility,poor stability and low absorption defects of AST,its application are greatly limited.The loading AST of nano-delivery system is helpful to overcome the above disadvantages and improve its bioavailability.Zein is the main storage protein in corn,which contains more than 50% hydrophobic amino acids,and it is a nontoxic nano transport carrier.In recent years,zein-based nanoparticle transport systems loaded with bioactive components have been extensively studied.In this paper,AST loaded nanoparticles were prepared by antisolvent method with zein as nano carrier and sodium casein as stabilizer,and the nanoparticles were characterized;The pretreatment method of rat plasma was optimized,the HPLC quantitative method of trace AST in plasma was established,and the enhancing effect of zein nano carrier on the bioavailability of AST in rats was determined;Furthermore,the absorption,metabolism,excretion and tissue fraction of AST in rats were studied;Finally,the effects of four P-gp inhibitors(Tax,TPGS,Ver and ?-CD)on the bioavailability of AST in nanoparticles were studied.The results were as follows:(1)Nanoparticles loaded with AST were successfully prepared by anti-solvent method.The sizes of nanoparticles with different mass ratios(AST and zein,1:1 to1:6)ranged from 132.00 nm to 152.91 nm,and the PDI values were all less than 0.3,indicating uniform particle size distribution.The mass ratios of AST,Zein and SC after optimization were 1:1:2.In this proportion,the particle size and potential of nanoparticles were 152.91 nm and-40.43 m V,respectively,and the EE% and LE%were 80.18% and 21.86%,respectively.The SEM image shows that the nanoparticles are spherical,with smooth surface and good redispersibility in water.The results of XRD and DSC analysis indicated that AST exists in amorphous form in nanoparticles.The hydrophobic forces and hydrogen bonds between the AST and zein,suggesting that the AST was encapsulated in the nanoparticles rather than adsorbed.The diffusion of astilbin from nanoparticles was significantly faster than that of astilbin suspensions in both simulated gastric and intestinal fluids.Astilbin was relatively stable in simulated intestinal fluids,and the encapsulation in the nanoparticles showed a slight stability improvement effect.(2)The optimal plasma pretreatment method was determined by optimization.In addition,the HPLC method established in this study meets the requirements for the determination of novoside in pharmacokinetic studies in terms of specificity,linearity,LLOD(4.8 ng/m L),LLOQ(16.3 ng/m L),precision(<4%),accuracy(>90%)and stability(86.34%-106.16%).The results of pharmacokinetic studies showed that the absolute bioavailability of AST increased from 0.32% to 4.40% in rats through nanoparticles fabrication,which was 13.75-fold enhanced.(3)The excretion,tissue distribution,and metabolic profile of astilbin in rat were studied by HPLC and UPLC-QTOF-MS.Astilbin underwent isomerization in the small intestine,and its four isomers were found in feces.Besides,taxifolin,the aglycone of astilbin,and its further metabolites by gut microbes through hydrogenation,dehydration,and ring-fission were found.The total feces excretion of astilbin was about 18.9% of administration.The forming of zein caseinate nanoparticles can significantly delay and reduce the feces excretion of astilbin(14.4%).Astilbin and its isomers were absorbed in their intact form.The main metabolites found in plasma and tissues were the methylated products.Astilbin was rapidly distributed in various tissues including brain and maintained relatively high concentration in heart.Compared with other tissues,significantly higher concentration and longer duration of astilbin were found in the gastrointestinal tract.Astilbin and its isomers were excreted in their intact and methylated form in urine,however the amount of excretion in urine is very small,so HPLC can not quantify it.(4)By studying the effects of four P-gp inhibitors on the bioavailability of AST in nanoparticles,it was found that the half-life of AST was delayed by ?-CD,and the concentration of AST in plasma was as high as 315.4 ng/m L(10 min)and 344.2ng/m L(0.5 h)after oral administration of Ver-AST-ZNP,more than twice as high as that of the ast-znp group.However,the absolute bioavailability of AST-ZNP,TPGS-AST-ZNP,?-CD-AST-ZNP,Tax-AST-ZNP and Ver-AST-ZNP were 1.56%,1.06%,1.04%,0.87% and 1.68%,respectively,showing no significant difference.The results showed that the four auxiliary agents had no significant effect on the absorption of AST in nanoparticles.