Study On Absorption Mechanism Of Quercetin And Its Derivatives In Caco-2 Cells

Flavonoids, the natural generated compounds with alpha or beta phenyl of benzene thick pyrone, widely exist in a lot kinds of Chinese herbs, fruits, vegetables and other plant or food, and present a huge diversity of structure and physiological function. Quercetin, is one of the most common flavonoids,which widely exists in fruits and vegetables, can play a beneficial health protection function on hunman beings. The functions of protection are including anti-oxidation, anti-inflammatory, vasodilatation, antitumor, etc. The molecular structure of the quercetin is containing multiple polar hydroxyl groups. Its lipotropy is weak. Hydroxyl in the structure of molecular interaction form hydrogen bonds, causing higher lattice energy, and its water solubility is weak as well.(7 ug/m L).According to the different chemical properties of hydroxyl group, we choose quercetin as leader to synthesis the 3,7,3’,4’-O-tetraethyl acetate quercetin. In this paper we studied the 3,7,3’,4’-O-tetraethyl acetate and quercetin by means of purification as well as the physical and chemical properties and caco-2 model. Simulating the intestinal cells, was used to study the mechanism of quercetin and ethyl acetate quercetin across membrane absorption metabolism.We choose quercetin as leader to alkylation decoration and to improve the fat-soluble of compound, which blocking its first effect in the process of digestion in the body, so as to improve its bioavailability. Using silica gel column chromatography, and the preparation of type liquid purification to separate the products, then identify the structure characterization. We select the highest yield and strongest antioxidant effect, the 3,7,3’,4’-O-tetraethyl acetate quercetin, as the drug absorption model.Through chemical method, we compared the physical and chemical properties of quercetin and its derivatives, and verified whether it raised its own fat soluble. The shake flask-HPLC method is used to test oil-water partition coefficient of drug in different media, preliminarily studing the enhancement of the fat-soluble of derivatives.By establishing caco-2 cell models to evaluate drug concentration in different p H, temperature, and ethylene glycol acetate(EGTA) of quercetin and 3,7,3’,4’-O-tetraethyl acetate quercetin under the action of the influence of the intestinal absorption transfer. And the transport inhibitor is used to study its main transporters in the transfer process, and comprehensively evaluate the absorption of quercetin and its derivatives of transfer mechanism.Results were as follows:1. By using(HPLC) method for determination of quercetin and 3,7,3’,4’-O-tetraethyl acetate quercetin in water and the different concentration buffer of salt solution at 37 ℃, quercetin equilibrium solubility in water is more than 3,7,3’,4’-O-tetraethyl acetate quercetin. The shaker-HPLC method, determinated those compounds in octanol-water, oil-water partition coefficient of fluid system. The measured results show that 3,7,3’,4’-O-tetraethyl acetate quercetin’s fat-soluble was higher than that of quercetin after esterification modification.2. Using Caco-2 cells model and the LC/MS methods to evaluate the absorption and transport mechanism of quercetin and ethyl acetate quercetin across Caco-2 cells monolayer. Results show that the transmembrane transport of quercetin mainly relies on the export-oriented transporters P-gp and MRP2, Eaq4 transmembrane transport mechanism is mainly passive diffusion.3. p H optimization of quercetin and Eaq4 in Caco-2 membrane across the plasma membrane is differ, the reason of the phenomenon may be due to the change of its molecular structure. Two kinds of compound optimization in Caco-2 on the cell membrane transport across the membrane is temperature dependent, the reason is the active efflux and passive diffusion both have close relationship with the change of temperature.