Pharmacokinetics And Quantitative Evaluation Of Hepatic And Intestinal First Pass Effect Of Hypeircin In Rats

Background: The oral drug absorption will experience the first-pass metabolism whichreduce the drug bioavailability to affect the clinical efficacy.Nowdays it has been widelyhypothesized that intestinal apical secretion and CYP3A4-mediated metabolism mayprofoundly affect a drug’s bioavailability;CYP3A4is a major phase I drug metabolizingenzyme that potentially mediates the biotransformation of more than60%of konwndrugs.Hypericin is the most biologically active substances in Hypericum perforatum L.Which has variety of pharmacological effects such as antidepressant,antitumor,antiviral,antiinflammatory,antibacterial and attentioned by domestic and internationalpharmaceutical market.However studies show that the oral administrationbioanailability of hypericin is very low,and continuous administration can not improveits bioavailability.Another research showed that Hypericum can induce CYP3A4expression.So we suggest that the first-pass metabolism may cause the lowbioanailability of hypericin,and we need to improve it.Currently,few studies haveresearched on the pharmacokinetics of the hypericin.Objective:The aim of this research was to explore the effects of intestinal and hepaticextraction on the bioavailability of hypericin and the possible involvement ofcytochrome CYP3A4in this study in rats.Methods:The current research was carried out by intestinal and vascular access ported（IVAP） rats to quantify and differentiate the components of intestinal and hepatic firstpass extraction of hypericin mediated by CYP3A4.Hypericin wan administered byintraduodenal instillation(id,100⁴00mg·kg^-1),intraportal infusion(ipv,50²00mg·kg^-1) or intravenous injection(iv,50²00mg·kg^-1).High-performance liquid chromatographywas used to determine the blood concentrations of hypericin.Extraction ratios in theliver and intestinal tract were determined from the area under the plasma concentration-time curve（AUC）.The roles of intestinal metabolism by CYP3A4on the first passintestinal extraction of hypericin was differentiated by using ketoconazole（an inhibitorof CYP3A4）.Hypericin was administered by id,ipv or iv to rats alone after30min the idadministration of ketoconazole(60mg·kg^-1).Results: The method was proved to be linear in the range of5ng·ml^-1～250ng·ml^-1thestandard curve for y=25997x-77321, r=0.9991.5ng·ml^-1、25ng·ml^-1、250ng·ml^-1Hypthe days coefficient of variation were1.30%、1.00%、1.02%（n=5）;day coefficientsof variation were4.36%、1.23%、2.31%（n=5）;recoveries were71.9%、74.9%、70.4%.In IVAP rat model, After id administration of various doses,all reached peakconcentration within20mins, pharmacokinetic parameters of AUC were10.14±1.41,28.77±6.22,57.50±4.94,respectively.After ipv administration of variousdoses AUC were107.48±11.56,184.05±30.20,257.42±32.50,respectively.After ivadministration of various doses AUC were100.69±9.17,224.16±28.78,310.19±41.50,respectively.AUC of hypericin were increased after propotionally after id,ipv,and ivadministration at various doses. When give the same dose of hypericin,the AUCidwaslower than AUCipvand AUCiv（p<0.05）,but there has no difference between AUCipvandAUCiv.The bioavailability after id administration of100、200mg·kg^-1of hypericin were4.53±0.6%,9.27±2%,respectively;the EHwere17.89±4.82%,17.01±9.48%,respectivelyand EIwere94.49±1.73%,88.82±3.09%,respectively.Compared with the controlgroup,the presence of ketoconazole(60mg·kg^-1) significantly increased AUC of idadministered hypericin,while it had no significant effect on hypeicin administered byipv and iv ports.Conclusion: In this study we establish a method using high-performance liquidchromatography analysis with fluorescence to determination hypericin in ratplasma.This method is good,can be used to analysis the pharmacokinetics of hypericin in rat. Oral hypericin experience intestinal first pass metabolism in rats,and intestinalfirst pass metabolism was higher than that of in liver. Intestinal CYP3A4is involved inintestinal first pass metabolism,but it doesn’t play a majoy role in this process. In thisresearch increase the does of hypericin,the bioavailability will increase.