A Study On The Absorption And Excretion Of Tea Polyphenols In Rats By The Effect Of High-fat Diet

The tea polyphenols（TP）,mainly including catechins,possesses various biological activities such as antioxidative,anti-inflammatory,antibacterial and antiarthritic.Moreover,some clinical and epidemiological investigations suggested that tea and tea polyphenols had health-protective action against hyperlipidemia or obesity.Yet,the pharmacokinetics of tea polyphenols was less reported in hyperlipidemia or obesity model or the effect of high-fat diet.The efficacy of active compounds depends on many factors related to their pharmacokinetic properties.For example,the dose or food intake could influence the absorption and metabolism of tea polyphenols.Tea is usually consumed in combination with milk in Europe and America.It can also be consumed with butter in the northwest China,such as Tibet and Inner Mongolia.To investigate the pharmacokinetics of seven catechins in rats,a rapid and sensitive ultra-high performance liquid chromatography tandem mass spectrometry（UHPLC-MS/MS）method was developed.Systematical study on the absorption and metabolism of catechins in plasma or other biological fluids were proceeded,for predicting the influence of pharmacokinetics by high-fat diet and promoting its rational application for further study.The results were as follows:（1）A UHPLC-MS/MS method was developed and validated for the determination of seven catechins in rat plasma.The rat plasma was extracted with simple liquid-liquid extraction using ethyl acetate.Plasma samples were separated by UHPLC on a Hypersil GOLD C18 column using a mobile phase consisting of methonal-0.05% formic acid in water with gradient elution.The total run time was 10.5 min and seven catechins（EGCG,EGC,EC,GCG,GC,C and ECG）were efficiently separated.The detection was performed on a selected reaction monitoring using the respective transitions m/z289.070→109.010 for（-）-epicatechin/（+）-catechin,305.089→125.228 for（-）-epigallocatechin/（+）-gallocatechin and 441.150→169.325 for（-）-epicatechin gallate and 456.840→169.257 for（-）-epigallocatechin gallate/（+）-gallocatechin gallate.The validated results show that the relative standard deviations（RSD）,precision,stability and recovery were in accordance with relevant regulations,which suggested the UHPLC-MS/MS method could be applied to determine the concentration of catechins in rat plasma precisely.（2）Normal rats and obesity rats induced by high-fat-diet（n=6/group）received an oral gavage of tea polyphenol（TP,700 mg/kg）.In obesity rats,the area under the serumconcentration-time curve（AUC0-t）values for（-）-epicatechin,（-）-epicatechin-3-gallate,（-）-epigallocatechin-3-gallate and（+）-catechin were increased by 219%,35%,13% and185% compared to normal rats,respectively,but those of（-）-epigallocatechin,（-）-gallocatechin and（-）-gallocatechin gallate were decreased by 74%,73% and 68%.Additionally,the maximal concentrations（Cmax）of various catechins in obesity rats were all significantly decreased expect for（+）-catechin.The obesity rats presented the different pharmacokinetics parameters of catechins from normal rats.（3）The distribution of tea polyphenols in normal and obesity rats’ digestive tract（including stomach,small intestine,appendix,colon and rectum）was studied,and the influence of distribution of seven catechins was also conducted.The result showed a significant difference in stomach and small intestine between this two groups.For example,in obesity rats,the content of EGCG in stomach and small intestine significantly decreased.（4）The maximum plasma concentration(C_max)of EGCG,EGC,EC,GCG,GC and ECG were significantly decreased by 51%,49%,76%,69% and 57% with co-administration of butter,but the mean residence time（MRT）of EGCG,EGC,EC,GC and ECG were significantly increased.The area under plasma concentration-time curve（AUC）of catechins was not affected by butter.These resultsindicated that the absorption rate of catechins was inhibited by butter,but the residence time of catechins was prolonged so that the total absorbed amount of catechins was not affected.Furthermore,the fecal catechins were all significantly increased by butter.The total fecal amount and excretion ratio of all catechins were increased highly.The biliary excretion of EGCG,EGC,EC,GCG and GC was significantly increased by co-administration of butter.