土荆皮乙酸的代谢产物和代谢途径

Metabolic pathway and metabolites of pseudolaric acid B

综合运用体内实验和多种体外实验模型,分析了土荆皮乙酸(pseudolaric acid B,PB)的代谢情况。在口服和静脉注射给药实验中,使用HPLC和HPLC-ESI/MSn方法在大鼠血、尿、粪和胆汁样品中都检测到去甲基土荆皮乙酸(土荆皮丙2酸,pseudolaric acid C2,PC2),各种样品中几乎都检测不到原形药物,PC2是PB特异性的代谢产物。PB在肠内菌抑制大鼠模型中的代谢情况与正常组一致,说明其代谢与肠内菌无关。在人工胃、肠液中分别孵育48 h均无明显变化,说明胃蛋白酶和胰蛋白酶都不是主导PB代谢的因素,在胃肠道的pH环境下PB也是稳定的。在体外大鼠肝微粒体孵育模型中,PB仅有极少部分被代谢成为脱甲氧基或脱甲氧基脱羧基的产物,说明其代谢也不是由肝微粒体酶主导的。在体外全血孵育模型中,PB在1 h内被逐渐代谢成PC2,并表现出了与孵育时间相关的动力学特点。由此推测土荆皮乙酸一进入血液就被迅速代谢成PC2,以致于在各种样品中都几乎检测不到原形药。这种快速的代谢应该是通过血浆酯酶对PB的C-19酯键的迅速水解而实现的。本文首次初步阐明了PB在体内的代谢途径,对于明确中药土荆皮的有效物质基础、体内活性形式及其作用机制都具有重要意义。

The metabolic profile of pseudolaric acid B（PB） was investigated by using in vivo and in vitro tests.Pseudolaric acid C2（PC2） was identified as the specific metabolite of PB in plasma,urine,bile and feces using HPLC and HPLC-ESI/MSn after both oral and intravenous administration to rats,and almost no prototype was detected in all kinds of samples.The metabolic behaviors of PB orally administered in rats treated with antibiotics to eliminate intestinal microflora were identical with those in untreated rats,demonstrating that the metabolism of PB is independent of intestinal microflora.PB was stable in 48 h respective incubation with artificial gastric juice and artificial intestinal juice,suggesting that neither pepsin nor trypsin is in charge of metabolism of PB,and also demonstrating that PB is stable in both pH environments of gastric tract and intestinal tract.In vitro research on metabolism of PB in rat liver microsomes incubation revealed that little PB was metabolized and that the proposed metabolites were the demethoxy and demethoxydecarboxy products of the prototype.The amount of metabolites was extremely low compared with the prototype,indicating that liver microsomes are not responsible for the metabolism of PB either.PB was gradually metabolized into PC2 during 1 h in whole blood incubation in vitro,and the metabolic process showed dynamically dependent manner with incubation time.Once absorbed into blood,PB was quickly metabolized into PC2,accordingly,little prototype was detected in all kinds of samples.The metabolism was attributed to the rapid hydrolysis of C-19 ester bond by plasma esterase.These results clarified the metabolic pathway of PB for the first time,which was of great significance to identify the in vivo active form and interpret acting mechanism of the active compounds of P.kaempferi.