Preparation Of Tea Polyphenols Nano-Emulsion And Their Absorption Kinetics

Tea polyphenols are the main active compounds of green tea,but their poor chemical stability and low oral bioavailability limits its usage in food and drug field.Hence,the objective of this study was to investigate the effect of nano-emulsion（o/w）encapsulated tea polyphenols on the physicochemical stability,in-vitro digestion and in-vivo metabolism bioavailability.In the present study,the nano-emulsion was constructed with corn oil and emulsified Tween 80（polysorbate 80）and Camellia saponins by high-pressure homogenization,obtained the o/w type TP nano-emulsion（Nano-A）,TP saponins nano-emulsion（Nano-B）and saponins nano-emulsion（Nano-C）.Nano-A,Nano-B and TP solution were put in the temperature humidity chamber at 4,25 and 40℃individually.Particle size,ZETA potential,p H and polyphenol content were analyzed every 5 days.The digestibility of main catechins and the changes of total saponins in Camellia oleifera during the simulating in-vitro digestion were analyzed to predict the metabolism of nano-emulsion in rats.According to existing research the metabolism of catechins in rats,SD rats were subjected to intragastric administration of Nano-A and tea polyphenols aqueous solution,and the content of catechin was determined.To sum up,the results suggest that nano-emulsion can improve both of the bio-accessibility and oral bioavailability by in-vitro and in-vivo model.The main results are as follows:（1）Three kinds of nano-emulsion prepared by Nano-A,Nano-B and Nano-C,the method adopts high pressure homogenization（1000bar,5 cycles）,the emulsion size reaches the nanometer level,the absolute value of ZETA potential between 30～60m V,the polydispersity index is relatively low,so the emulsion was relatively stable.（2）The encapsulation efficiencies of Nano-A and Nano-B were 17.4%and 15.69%,respectively.Although it is not high,but it has a certain protective effect on catechins,and the preparation cost is low,the operation is simple and easy to prepare.（3）The storage experiment of Nano-A and Nano-B showed that Nano-A and Nano-B went bad about 25days and 100 days at 25℃.Therefore,for prolonging the storage time of emulsion,the use of natural Camellia saponins as emulsifier was better than Tween 80.The particle size and potential data in the storage process suggested that Nano-A and Nano-B did not show obvious particle aggregation in the storage time,and the emulsion was so stable.（4）Nano-A and Nano-B were stored at 4,25 and 40℃,respectively.The results showed that the stability of the emulsion was best at 4℃,and it can be concluded that nano-emulsion has a better protective effect on polyphenols.（5）In the three stages of in-vitro digestion:oral digestion after 10min,in Nano-A,EGC EC and the rate of recovery was 77.29%,the recovery rate of EGCG were 90.58%and 87.36%,GC,GCG and ECG recovery rate remained unchanged;the main catechin nano-b recovery rate was more than 90%,there may be part of the catechins degradation in solution the weak acid environment.Gastric digestion 2h,in addition to the complete metabolism of GC,the rest of the catechins were not significantly degraded,it might be conducive to the stability of the acid environment of catechins and nano-emulsion had a protective effect on catechins.After the small intestine digestion 2h,catechins have obvious degradation,it is possible that the small intestine digestion is neutral or slightly alkaline condition,which is easy to auto oxidation decomposition of catechin,and the protective effect of Nano-A on EGCG,GCG and ECG is better than that of Nano-B.（6）According to the results of pharmacokinetic parameters,nano-emulsion can effectively improve the oral bioavailability of two main catechins EGCG and EGC in tea polyphenols.The maximum concentration(C_max)of EGCG and EGC in rats was 166.71μg L^-1and 59.91μg L^-1.The area under the curve（AUC）was 17.15mg L^-1 min and 6.11mg L^-1min.The C_max of tea polyphenols aqueous solution EGCG and EGC was 258.84μg L^-1and26.58μg L^-1.The area under the curve（AUC）was 13.32mg L^-1 min and 4.76mg L^-1min.Compared with TP aqueous solution,the results showed that the maximum plasma concentrations(C_max)of EGCG and EGC were significantly decreased,but their area under concentration-time curve（AUC）had increased,so nano-emulsion had the slow release effect on the encapsulated catechins.