| Objective:Cytochrome P450 enzyme 1A2(CYP1A2),Cytochrome P450 enzyme 2A6 (CYP2A6),N-acetyltransferase-2(NAT2),and xanthine oxidase(XO) play an important role while the drugs are metabolized and carcinogens are activated,their activation is closely related to curative effect or toxicity of a lot of drugs and susceptibility of some tumors,different active state of this enzymes must has certain influence on transformation of chemical material in vivo.To investigate the effect of ginkgo biloba tablets on CYP1A2,CYP2A6,NAT2 and XO activities in human and to forecast the drug-drug interaction of ginkgo biloba tablets,the activities of CYP1A2, CYP2A6,NAT2 and XO are assayed by metabolic probe which are contributed to predict medicine curative effect,prevent and mitigate medicine adverse effect, improve drug safety and instruct clinician to prescribe rationally.Methods:Caffeine was used as a metabolic probe for CYP1A2,CYP2A6,NAT2 and XO,a HPLC method of metabolites of caffeine in the urine with direct injection was established for assuring the assay accuracy.The Shim-pack VP-COD column(4.6mm×150mm,5μm) and Shim-pack C18 pre-column were used.The mobile phase was acetonitrile and the gradient program was acetonitrile 2.5%to 10% in 0 to 24 min.The flow rate was 1.0mL.mim-1,and the column temperature was 25℃.The detective wavelength was at 280nm.In thirty volunteers,before and after ginkgo biloba tablets administration,urine samples were collected.The contents of five major metabolites of caffeine,5-acetylamino-6-formylamino-3-methyluracil(AFMU),1-methylxanthine(1X),1-methyluricacid(1U),1,7-dimethylurica cid(17U) and 1,7-dimethylxanthine(17X) in the urine were determined by RP-HPLC with direct injection method,and then the activity of CYP1A2,CYP2A6,NAT2 and XO were evaluated by respectively calculating the(AFMU+1X+1U)/17U, 17U/(AFMU+1U+1X+17X+17U),AFMU/(AFMU+1X+1U)and 1U/(1X+1U).The effect of therapeutic dose ginkgo biloba tablets administrated for 28 days were investigated simultaneously on CYP1A2,CYP2A6,NAT2 and XO respectivelyResults:A new HPLC method of five metabolites of caffeine in the urine with direct injection was developed.The method is simple,rapid and accurate.It was found that the average activities of CYP1A2 were 2.976±1.428,3.021±1.318 before treatment,after taking medicine 28days respectively,There were no statistical significancet between before treatment and after taking medicine 28 days.It was found that the average activities of CYP2A6 were 0.227±0.076,0.227±0.072 before treatment,after taking medicine 28days respectively,There were no statistical significance between before treatment and after taking medicine 28 days.It was found that the average activities of NAT2 were0.447±0.172,0.391±0.147 before treatment,after taking medicine 28days respectively,There were statistical significance between before treatment and after taking medicine 28 days.It was found that the average activities of XO were 0.723±0.060,0.728±0.074 before treatment,after taking medicine 28days respectively,There were no statistical significance between before treatment and after taking medicine 28 days.Conclusions:The method to measure simultaneously the activity of CYP1A2, CYP2A6,NAT2 and XO should contribute to simplifying and optimizing the caffeine drug metabolizing enzyme assays.Ginkgo biloba tablets have no influence on CYP1A2,CYP2A6and XO,so ginkgo biloba tablets do not modify the efficacy of drugs taken simultaneously which were metabolized by CYP1A2,CYP2A6 and XO.But ginkgo biloba tablets may modify the efficacy of drugs which metabolized by NAT2 taken simultaneously in slow acetylator.It is necessary to further study the effect of ginkgo biloba tablets administrated for long-term or in large dose on CYP1A2,CYP2A6,NAT2 and XO in human.
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