Dean Brian, Chang Steve, Doss George A, King Christopher, Thomas Paul E
Department of Drug Metabolism, Merck & Co., Inc., Rahway, NJ, USA.
Arch Biochem Biophys. 2004 Sep 15;429(2):244-51. doi: 10.1016/j.abb.2004.06.023.
Enterolactone (ENL) and enterodiol (END) are mammalian lignans derived from the plant lignans matairesionol (MAT), secoisolariciresinol (SECO), and other dietary precursors. ENL was found to undergo extensive glucuronidation with rhesus liver microsomes to form O-glucuronides at both phenolic hydroxy groups. In addition to glucuronidation, ENL was found to be a good substrate for oxidative metabolism. The major products had a m/z of 313 or 295 by LC-MS analysis in negative ion mode and were determined to be products of monohydroxylation of ENL. The m/z 295 products were the result of a dehydration of the m/z 313 in the MS source. Addition of N-acetylcysteine (NAC) to the NADPH incubations resulted in a decrease of at least 2 major monohydroxylated products and the formation of a major and several minor new products with a m/z of 474. The major adduct was isolated, purified for NMR, and confirmed to be the NAC adduct of the ENL catechol. Incubations of ENL with liver microsomes containing UDPGA, NADPH, and NAC resulted in the formation of ENL-glucuronides; no NAC adducts were detected by LC-MS. Incubations of ENL with human and rhesus hepatocytes resulted in several metabolites. The major metabolites in hepatocytes were the glucuronic acid conjugates; minor amounts of the sulfate conjugate(s) and monohydroxylated products were also detected by LC-MS. Glutathione or other thiol adducts were not detected in hepatocytes. Conclusion. The high efficiency and specificity for the glucuronidation of ENL decrease its potential toxicity via CYP450 bioactivation.
肠内酯（ENL）和肠二醇（END）是源自植物木脂素开环异落叶松脂醇（MAT）、松脂醇（SECO）及其他膳食前体的哺乳动物木脂素。研究发现，ENL与恒河猴肝微粒体发生广泛的葡萄糖醛酸化反应，在两个酚羟基处均形成O-葡萄糖醛酸苷。除葡萄糖醛酸化反应外，ENL还是氧化代谢的良好底物。在负离子模式下通过液相色谱-质谱分析，主要产物的质荷比为313或295，经测定为ENL单羟基化产物。质荷比为295的产物是质荷比为313的产物在质谱源中脱水的结果。在NADPH孵育体系中加入N-乙酰半胱氨酸（NAC），导致至少2种主要单羟基化产物减少，并形成了一种质荷比为474的主要新产物和几种次要新产物。分离并纯化了主要加合物用于核磁共振分析，证实其为ENL儿茶酚的NAC加合物。将ENL与含有尿苷二磷酸葡萄糖醛酸（UDPGA）、NADPH和NAC的肝微粒体一起孵育，导致形成ENL-葡萄糖醛酸苷；液相色谱-质谱未检测到NAC加合物。将ENL与人及恒河猴肝细胞一起孵育产生了几种代谢产物。肝细胞中的主要代谢产物是葡萄糖醛酸共轭物；液相色谱-质谱还检测到少量硫酸共轭物和单羟基化产物。肝细胞中未检测到谷胱甘肽或其他硫醇加合物。结论。ENL葡萄糖醛酸化反应的高效性和特异性降低了其通过细胞色素P450生物活化产生的潜在毒性。
