Metabolism of Diosbulbin B In Vitro and In Vivo in Rats: Formation of Reactive Metabolites and Human Enzymes Involved
作者:Baohua Yang、Wei Liu、Kaixian Chen、Zhengtao Wang、Changhong Wang
DOI:10.1124/dmd.114.058222
日期:2014.10
Diosbulbin B (DB), a major constituent of the furano-norditerpenes in Dioscorea bulbifera Linn, exhibits potential antineoplasmic activity and hepatotoxicity. The metabolism and reactive metabolites of DB in vitro (with human and animal liver microsomes) and in vivo in rats were investigated. The human enzymes involved in DB metabolism were identified. DB was first catalyzed into reactive metabolites of 2-butene-1,4-dial derivatives dependent on NADPH and then trapped by Tris base or oxidized to hemiacetal lactones (M12 and M13) in microsomal incubations. Tris base was used as buffer constituent and as a trapping agent for aldehyde. Methoxylamine and glutathione (GSH) were also used as trapping agents. DB metabolism in vivo in rats after oral administration was consistent with that in vitro. The structures of M12 and M13, as well as mono-GSH conjugates of DB (M31), were confirmed by nuclear magnetic resonance spectroscopy of the chemically synthesized products. The bioactivation enzymes of DB were identified as CYP3A4/5, 2C9, and 2C19. CYP3A4 was found to be the primary enzyme using human recombinant cytochrome P450 enzymes, specific inhibitory studies, and a relative activity factor approach for pooled human liver microsomes. Michaelis-Menten constants K m and V max were determined by the formation of M31. The reactive metabolites may be related to the hepatotoxicity of DB. The gender difference in CYP3A expression in mice and rats contributed to the gender-related liver injury and pharmacokinetics in mice and rats, respectively.
Diosbulbin B (DB) 是黄药子中呋喃去甲二萜的主要成分,具有潜在的抗肿瘤活性和肝毒性。研究了 DB 的体外(人和动物肝微粒体)和大鼠体内的代谢和反应性代谢物。鉴定了参与 DB 代谢的人类酶。 DB 首先被催化成依赖于 NADPH 的 2-丁烯-1,4-二醛衍生物的反应性代谢产物,然后被 Tris 碱捕获或在微粒体孵育中氧化为半缩醛内酯(M12 和 M13)。 Tris 碱用作缓冲液成分和醛的捕获剂。甲氧基胺和谷胱甘肽(GSH)也被用作捕获剂。 DB口服后在大鼠体内的代谢与体外一致。 M12和M13以及DB(M31)的单GSH缀合物的结构均通过化学合成产物的核磁共振波谱证实。 DB的生物活化酶被鉴定为CYP3A4/5、2C9和2C19。使用人重组细胞色素 P450 酶、特异性抑制研究以及汇集人肝微粒体的相对活性因子方法,发现 CYP3A4 是主要酶。米氏常数 K m 和 V max 由 M31 的形成确定。活性代谢物可能与DB的肝毒性有关。小鼠和大鼠中 CYP3A 表达的性别差异分别导致小鼠和大鼠中性别相关的肝损伤和药代动力学。