The Thermal Analysis And Metabolism Study Of Aucubin And Gentiopicroside

Aucubin and gentiopicroside are both iridoids.Aucubin is the principal and abundant component of Eucommia ulmoides Oliv.,Plantago asiatica L.,Rehmannia glutinosa Libosch.,Scrophularia ningpocnsis Hemsl.It possesses liver-protective, antiviral,anti-inflammatory,antioxidant,antileukemic activities,and so on.Recently,it is found to be a novel topoisomeraseⅠinhibitor which increases interest in its possible use in cancer chemoprevention and antitumoral therapy.Gentiopicroside is the principal component of Gentiana macrophylla Pall.and Gentiana straminea Maxim.It has remarkable liver-protective and anti-inflammatory activities.In this thesis,the thermal characters and metabolism of aucubin and gentiopicroside were investigated,including thermal decomposition kinetics,distribution in rat tissues,pharmacokinetics,metabolism in gastro and liver,and so on.The detailed descriptions are listed below.Part one:The thermal analysis of aucubin and gentiopicrosideThermolysis of aucubin and gentiopicroside were studied using various thermo-analytical techniques.Kinetic analysis of non-isothermal thermogravimetry data was done.The activation energy of aucubin at the two decomposed processes were 125.71 kJ·mol^-1and 166.80 kJ·mol^-1,respectively.The activation energy of gentiopicroside at the two decomposed processes were 148.40 kJ·mol^-1and 33.90 kJ·mol^-1, respectively.The pyrolysis process was investigated by online-coupled thermogravimetry-infrared spectroscopy technique.The possible thermal degradation mechanisms of aucubin and gentiopicroside were discussed according to the analysis results of the escaped gases and residues. Part two:The effect study of compatibility on the pharmacokinetics of gentiopicrosideCompatibility of Chinese medicinal herbs is the main method of medicinal application in clinic and also the basis of making up formulae of Chinese medicinal herbs. A HPLC method was established for the simultaneously quantitative determination of gentiopicroside and glycyrrhizin in rabbit plasma,and it was applied to study the effect of compatibility on the pharmacokinetics of gentiopicroside and glycyrrhizin.Plasma samples from rabbits that were administrated intravenously with gentiopicroside and/or glycyrrhizin at the 50mg·kg^-1dosage,were detected using the HPLC method.The concentrations versus time data were analyzed using DAS program(2005).The results showed that glycyrrhizin and other components in Gentiana macrophylla Pall.could affect the pharmacokinetics of gentiopicroside,but gentiopicroside had no effects on glycyrrhizin.Part three:The pharmacokinetic and distribution studies of aucubin in ratA simple,inexpensive and accurate high-performance liquid chromatographic method was developed and validated for the determination of aucubin in rat plasma and tissues.Acceptable intra-day and inter-day precision and accuracy at high,medium and low concentration ranged from 0.22%to 4.18%and 0.25%to 4.53%,respectively.Good assay recoveries were obtained with a single and relatively fast precipitation protein step. The mean assay recovery and extraction recovery of aucubin were 94.35%and 91.02%, respectively.The parameters were calculated using DAS software.The values of t_1/2β, V_d,CL and AUC were 32.23min,0.13L·kg^-1,0.003 L·min^-1·kg^-1and 27620 min·mg·L^-1in the plasma,respectively.Considerable aucubin was present in kidney and liver. Aucubin concentration was highest in kidney and remained much higher than that in other tissues over the experiment course.Lung,heart,spleen and testis were also detected to contain aucubin.The results closely conformed to the meridian tropism of Cortex Eucommiae and clearly demonstrated that aucubin was one of the material bases of the meridian tropism of Cortex Eucommiae. Part four:Study on the gastro metabolism of aucubin and gentiopicrosideThe gastro metabolisms of ancubin and gentiopicroside in artificial gastric solution were studied by TLSC.The effects of incubation time and substrate's concentration on metabolism were investigated.Three volume of ethyl acetate were added to stop the metabolism,and to extract the metabolite for 10 times.The TLSC results showed aucubin could quickly transformed in artificial gastric solution at 37℃.The major metabolite of aucubin was aucubigenin,which was not stable and easily further polymerized.About 20%aucubin were not hydrolyzed after incubation for 4h. Gentiopicroside wasn't observed transformation.The research suggested that aucubin might be transformed to aucubigenin in gastro,and oral administration was the effective and scientific way of Chinese medicinal herbs that contained aucubin.Part five:Study on the hepatic metabolism of aucubin and gentiopicrosideThe metabolic transformation of aucubin and gentiopicroside were studied by using rat liver microsomal incubation in vitro that contained the NADPH-generating system. The concentrations of aucubin and gentiopicroside were detected by TLSC and HPLC method after incubation for 4h.No changes were observed.After intravenous injection with different dosage of aucubin or gentiopicroside to rat for three days,the content of rat liver microsomes P450 was determined to be increased.The two components also could shorten the duration of hypnosis induced by pentobarbital sodium in mice(P＜0.05).The effects of the two drugs on mice spontaneous movements and equilibrium function were also observed.