Pharmacokinetics Of Herbal Injeceable Microspheres

Centella asiatica have many kinds of pharmacological effect such as detoxifcation and detumescenceto speed wound concrescence,to promote biosynthesis,anti gastric ulcer and so on.It has been used for treatment of skin diseases,rheumatism, inflammation,syphilis,mental illness,epilepsy,diarrhea and wounds.Nowadays, asiaticoside tablets was taken three time a day,it need continuous therapy usually for 3 to 6 months,because of long term therapy and frequent administration,long trerapy treatment cycle,it brings great inconvenience to patients.In order to prolong the time-effect of asiatic acid,reduce administration times,improve patients' compliance, asiatic acid microspheres was prepared by emulsion-crosslinking method,which can bring patients convenience,be taken easily.In this study,pharmacokinetic of asiatic acid-chitosan microspheres and the hydrolysis method of metabolism of asiatic acid were investigated emphatically.In this study,a precolumn derivatization reversed-phase high-performance liquid chromatography(RP-HPLC) method with UV-vis detection of concentration of asiatic acid(AA) in rats plasma is described.Plasma sample were treated by addition of madecassic acid as internal standard and protein precipitation.Moreover,AA was derivatized with p-Toluidine(PTD).After derivation,the sensitivity of asiatic acid was increased greatly.In conclusion,a simple,sensitive and selective precolumn derivatization HPLC method with UV detection for the determination of total concentration of AA in rats' plasma was developed.The assay could satisfy the pharmacokinetics study in rats after intramuscular injection of Asiatic acid microspheres. Sprague-Dawley rats(male,250±20 g) were used to Pharmacokinetics study.The study was conducted as a single dose.Diet was prohibited for 24 h before the experiment while water was taken freely.Dosage was 100mg/kg by intramuscular injection.The pharmacokinetic parameters were calculated with the Drug and Statistics computer program(PKS,Shanghai Magnsoft Consulting).The area under the plasma concentration-time curve(AUC) and the area under the first-moment time curve (AUMC) were calculated by the trapezoidal method,and extrapolated to infinity using the last measurable plasma concentration and the terminal elimination rate constant. Mean residence time(MRT) was calculated using the equation MRT=AUMC/AUC. The terminal elimination half-life(t_1/2) was derived by linear regression analysis of the terminal phase of the plasma concentration-time curve.The pharmacokinetic results show that asiatic acid-chitosan microspheres can keep on releasing for more than ten days in rats after single intramuscular injection,with plasma concentration be stable.Main pharmacokinetic parameters obtained were:AUC 10.52±3.41 d·μg/mL, Tmax 1.65±0.78 d,MRT 4.01±0.42 d.Data was accordance with one-compartment model.It's reported that Asiatic acid can be metabolized into its glucuronic acid conjugations and sulfuric acid conjugations in vivo.Asiaticoide was selected as model drug in this paper.Hydrolyzation needed 3 hours at 60℃with the ethanol(70%) solution of 1mol/L Sodium hydroxide.Asiatic acid in the hydrolysate was detected by RP-HPLC.The hydrolysis method is convenient and stable for feces samples,the RP-HPLC method is a very accurate method,for the quantitative determination of the metabolite of Asiatic acid.In summary,based on the frontal research which had been done,the analogues madacassic acid was considered as internal standard,p-Toluidine(PTD) was used as the derivatizing reagent,a assay of pre-column derivatization RP-HPLC for asiatic acid in rats plasma was developed which possessed strong specificity,high sensitivity and accuracy,high precision;On the other hand,pharmacokinetics of Asiatic acid microspheres was evaluated for the first time,and the microspheres can keep on releasing for more than ten days after single intramuscular injection.Moreover,the hydrolysis method of metabolites of Asiatic acid and hydrolysis condition of it was investigated further and systematically,what's more,it were applied to the hydrolysis of feces sample preliminarily.This study can provide experimental and theoretical basis for new drug Asiatic acid microspheres.