Preparation And Pharmacokinetics Study In Rats Of Scutellarein

Scutellarein,also known as scutellarin aglycon,is a polyhydroxylated flavonoid which could be hydrolyzed by scutellarin.Due to the outstanding pharmacological effects,such as the protective effects of cerebral ischemia,anti-inflammatory,anti-cancer,resistance to Parkinson's syndrome and the physicochemical properties like high fat-soluble and high permeability,scutellarein has received more attention in recent years.As a major component of breviscapine,scutellarin can be obtained in large quantities from the Erigeron breviscapus,a plant of Asteraceae.However,there is no other way but only by synthetic or biological conversion methods to attain great quantity of scutellarein,for its unstable chemical properties and its low content in plants.In this paper,the optimal preparation condition of scutellarein by scutellarin hydrolyzation,the physicochemical properties of scutellarin,the pharmacokinetics properties and the intestinal absorption characteristics of scutellarin in rats were investigated respectively.Firstly,scutellarein was prepared successfully by the hydrolization of scutellarin in a circumstance added certain acid.CCD-RSM,combined with the"Overall Desirability"theory,was used in this experiment to optimize the preparation conditions of scutellarein.To analyze the experimental results,the softwares SAS and Statistica 6.0 were utilized to conduct equation fitting of preparing conditions and to draw the 3D surface plots and the contour plots.The multivariate quadratic equation was then established as the multiple correlation coefficient R=0.8763,P=0.0347,Y=-5.9390+0.1259X₁+0.1226X₂-0.0049X₁²-0.0007X₂²+0.0004X₁X₂,which means the model was established significantly.The optimal preparation conditions were selected as follows:scutellarin and the solid-liquid ratio(g·L^-1)was at 15 and the reaction temperature was at 80°C.The grade of purified products after recrystallization purification could be up to or above 95%?HPLC?.Secondly,to investigate the stability of scutellarein in different media and circumstances with different pH values,different antioxidants or nitrogen,the HPLC-UV method was chosen to identify the disparities.The results showed that scutellarein was more stable in methanol than in aqueous media;the protection of nitrogen or antioxidants can favor the stability of scutellarein.If 0.4mg/kg ascorbic acid was added as an antioxidant or the medium was regulated at pH=5.4 with the protection of nitrogen protection,scutellarein can be stable in the medium at 37?within 4 hours?degradation less than 4%?,which suggests that the medium can be successfully performed in vivo,such as Long-circulating perfusion experiments or everted gut sacs.Thirdly,it is of great importance to operate the intravenous administration and orally administration when discovering the pharmacokinetic properties of scutellarein in rats.Plasma concentration was determined by HPLC-UV and DAS 2.0 was used to calculate pharmacokinetic parameters.After oral administration in rats,the half-life of the drug was 11.85h,the plasma concentration of scutellarein peaked at 1h and peak again at 9h,yet the second peak was smaller and less obvious.By analyzing the AUC values of intravenous administration and oral administration in the same molar dosage of scutellarein,the bioavailability of scutellarein in rats turned out to be 2.79%.While after intravenous administration,scutellarein was rapidly eliminated to its half-life in0.17h.There was no double-peak phenomenon in the curve of scutellarein concentration after intravenous administration.Afterwards,plasma samples,from intravenously administration and orally administration,were hydrolyzed by?-glucuronidase separately to demonstrate the glucuronidation of scutellarien in rats.After oral administration,the amount of scutellarein in the plasma samples were about 2-fold higher than that of the unhydrolyzed plasma samples,indicating that about half of the prototype drug was converted into its glucose combination after oral administration.Nevertheless,after intravenous administration,the overall content of scutellarein was about 3 times that of unhydrolyzed samples,implying that about 2/3 of the prototype drug was converted.The results demonstrate that scutellarein conjugates in rat after administered intravenously were clearly higher than orally.In the end,to study the effects of bile-duct ligation on intestinal absorption in rats administered with scutellarein,the long-circulating perfusion experiments were conducted.The drug residues in intestinal fluid was measured by HPLC-UV and compared to the origin drug concentration to calculate the absorption coefficient Ka,the absorption percentage P?%?and the absorption half-life T_1/2?h?.Consequently,comparing to other intestinal parts,the ileum performed best absorption properties,followed by duodenum,jejunum and colon.After bile duct ligation,the absorption coefficient of the intestinal slightly increased yet the percentage of absorption and the half-life of the drug decreased moderately to some extent,which illustrates that there may be enterohepatic circulation in the intestinal absorption of scutellarein in rats.