Study On Preparation And Hypoglycemic Activity Of Myricitrin Mixed Micelles

Myricitrin（MYR）is widely found in the bark,leaves and fruits of many plants.It is a flavonol compound with a polyphenolic hydroxyl group.However,its low solubility in water,poor bioavailability,instability and other factors have greatly restricted its clinical application.Therefore,the research idea of this subject was to prepare MYR mixed micelles by thin film dispersion method for improving its solubility and oral bioavailability.Meanwhile,this article would explore the hypoglycemic activity of MYR mixed micelles,in order to lay the foundation for multiple applications of MYR.ChapterⅠ:OverviewThis chapter systematically expounded the research situation of MYR,including its physicochemical properties,pharmacologic action and relevant preparations.Meanwhile,the formation characteristics,excipient types and preparation methods of micelles were analyzed and summarized.Finally,an overview of the pathological mechanism,harm and experimental research status of diabetes was carried out,which has laid a certain foundation for the in-depth study of this subject.Chapter II:Pre-prescription ResearchIn this chapter,HPLC was used to establish in vitro analysis method and standard curve equation of MYR.When the concentration of MYR was 2.5～250μg/m L,the linearity was satisfactory（R²=0.9998）.And a series of investigations and verifications were conducted on the methodology,and the precision and recovery rate of above method were all in line with the requirements.The MYR equilibrium solubility in three kinds of medium（p H 1.2,p H 6.8 and ultrapure water）were all lower than 40μg/m L,which reflected the poor water solubility of MYR,and provided theoretical reference for the follow-up study of drug release in vitro.ChapterⅢ:Preparation and in vitro characterization of MYR mixed micellesIn this chapter,two MYR mixed micelles were prepared by thin film dispersion method,and the formulation was optimized by single factor experiment and orthogonal experiment design.The optimized formulation of myricitrin-loaded-TPGS micelles（MLTM）was as follows:the mass ratio of phospholipid to sodium cholate was 3:2,the mass of PVPK30 was 60 mg,the mass of MYR was 40 mg,and the mass of TPGS was42 mg.The formula of myricitrin-loaded micelles（MLM）was as follows:the mass ratio of phospholipid to sodium cholate was 3:2,the mass of PVPK30 was 60 mg,and the mass of MYR was 40 mg.The measured droplet diameters of MLM and MLTM were severally 30.93±1.34nm and 26.42±0.89 nm,PDI were severally 0.173±0.023 and 0.135±0.017,Zeta potential were respectively 20.30±0.87 m V and 23.20±0.79 m V,and encapsulation rates were respectively 83.31±1.08%and 93.83±1.18%.TEM images of MLM and MLTM showed that they were spherical in shape and their distributions were relatively uniform.The results of in vitro drug release study revealed that among the three media（p H 1.2,p H 6.8 and ultrapure water）,the in vitro cumulative release rate of free MYR within 24 hours was lower than 35%,while that of MLM and MLTM respectively was higher than 55%and 70%,meanwhile percentage of cumulative liberation for MLTM exceeded that of MLM.This indicated that both MLM and MLTM could effectively improve the in vitro release behavior of MYR,and MLTM had more advantages.Besides,in vitro antioxidant results displayed that the scavenging effect of MLM and MLTM on DPPH free radical was comparable to that of free MYR,indicating that MLM and MLTM could retain their antioxidant capacity well.ChapterⅣ:Pharmacokinetic study of MYR mixed micelles in ratsIn this chapter,it was determined that vanillin was used as the internal standard,and biological samples in vivo were processed by ethyl acetate extraction.The in vivo standard curve equation was established by HPLC,and its linear relationship was good in the concentration range of 0.1～50μg/m L（R²=0.9987）.Meanwhile,the methodology was accordingly investigated,and these results showed that its precision and recovery rate met the requirements.Rats were given 300 mg/kg MYR,MLM and MLTM by intragastric administration for pharmacokinetic studies.The results showed that the serum concentrations of MLM and MLTM were significantly higher than that of free MYR.The half-life(t_1/2)of MYR,MLM and MLTM were severally 8.10±0.053 h,8.11±0.16 h and 9.21±0.23 h,and their AUC_{0-24 h} were separately 5.54±0.73 h·μg/m L,16.75±2.10 h·μg/m L and 19.65±2.78 h·μg/m L.Compared to free MYR,the t_1/2 of MLTM was delayed by 1.11 h and its AUC_{0-24 h} was increased by 3.55 times.It can be seen from the above results that MLM and MLTM could effectively improve the oral bioavailability of MYR,and MLTM has a better advantage than MLM.ChapterⅤ:Pharmacodynamics of MYR mixed micellesIn this study,the hyperglycemia symptoms in mice were induced by abdominal injection of STZ and intake of a high-fat diet.After 28 days of treatment,free MYR,MLM and MLTM all showed the therapeutic effects of lowering blood sugar level,improving glucose tolerance and promoting weight gain.Among them,the different dose groups showed significant difference in hypoglycemic effect（P<0.05）,suggesting a certain degree of dose dependence.In addition,according to the results of biochemical indexs detection,free MYR,MLM and MLTM all decreased the content of MDA,and increased the activities of SOD and GSH-Px in serum,indicating that free MYR,MLM and MLTM all had a certain antioxidant effect,meanwhile,high-dose MLTM had a better antioxidant effect.Besides,free MYR,MLM and MLTM also improved the damage of organ cells to a certain extent by observing the histopathological sections.It was found after comprehensive analysis that the hypoglycemic activity of MLTM was better than that of MLM and free MYR.In conclusion,MLTM had the more beneficial effect on lowering blood sugar,antioxidant activity and the function of repairing damaged organs.