大鼠肝微粒体酶对12-甲基苯并[a]蒽5,6-环氧化物对映体的立体选择性形成及水化作用。

Stereoselective formation and hydration of 12-methylbenz[a]anthracene 5,6-epoxide enantiomers by rat liver microsomal enzymes.

作者信息

Yang S K, Mushtaq M, Weems H B, Miller D W, Fu P P

机构信息

Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799.

出版信息

Biochem J. 1987 Jul 1;245(1):191-204. doi: 10.1042/bj2450191.

DOI:10.1042/bj2450191

PMID:3663145

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1148099/

Abstract

The K-region trans-5,6-dihydrodiols formed in the metabolism of 12-methylbenz[a]anthracene (12-MBA) by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats were found by chiral stationary-phase h.p.l.c. (c.s.p.-h.p.l.c.) analyses to contain (5S,6S)/(5R,6R) enantiomer ratios of 93:7, 88:12 and 97:3 respectively. The absolute stereochemistry of a 12-MBA trans-5,6-dihydrodiol enantiomer was elucidated by the exciton-chirality c.d. method. The 5,6-epoxides formed in the metabolism of 12-MBA by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats in the presence of the epoxide hydrolase inhibitor 3,3,3-trichloropropylene 1,2-oxide were isolated from a mixture of metabolites by normal-phase h.p.l.c., and their (5S,6R)/(5R,6S) enantiomer ratios were found by c.s.p.-h.p.l.c. analyses to be 73:27, 78:22 and 99:1 respectively. The absolute configurations of 12-MBA 5,6-epoxide enantiomers, resolved by c.s.p.-h.p.l.c., were determined via high-resolution (500 MHz) proton-n.m.r. and c.d. spectral analyses of the two isomeric methoxylation products derived from each of the 12-MBA 5,6-epoxide enantiomers. Enantiomeric pairs of the two methoxylation products were resolved by c.s.p.-h.p.l.c. The results indicate that enantiomeric 5S,6R-epoxide and 5S,6S-dihydrodiol were the major enantiomers preferentially formed in the metabolism at the K-region 5,6-double bond of 12-MBA by all three rat liver microsomal preparations. Optically pure 12-MBA 5S,6R-epoxide was hydrated predominantly at the C(6) position (R centre) to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 97:3. However, optically pure 12-MBA 5R,6S-epoxide was hydrated nearly equally at both C(5) and C(6) positions to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 57:43.

摘要

通过手性固定相高效液相色谱（c.s.p.-h.p.l.c.）分析发现，未处理、经苯巴比妥处理和经3-甲基胆蒽处理的雄性斯普拉格-道利大鼠肝脏微粒体制剂在代谢12-甲基苯并[a]蒽（12-MBA）过程中形成的K区域反式-5,6-二氢二醇，其（5S,6S）/（5R,6R）对映体比例分别为93:7、88:12和97:3。通过激子手性圆二色（c.d.）法阐明了12-MBA反式-5,6-二氢二醇对映体的绝对立体化学。在环氧水解酶抑制剂3,3,3-三氯丙烯1,2-氧化物存在下，从未处理、经苯巴比妥处理和经3-甲基胆蒽处理的雄性斯普拉格-道利大鼠肝脏微粒体制剂代谢12-MBA过程中形成的5,6-环氧化物，通过正相高效液相色谱从代谢物混合物中分离出来，通过c.s.p.-h.p.l.c.分析发现其（5S,6R）/（5R,6S）对映体比例分别为73:27、78:22和99:1。通过c.s.p.-h.p.l.c.分离的12-MBA 5,6-环氧化物对映体的绝对构型，通过对源自每种12-MBA 5,6-环氧化物对映体的两种异构甲氧基化产物进行高分辨率（500 MHz）质子核磁共振和圆二色光谱分析来确定。两种甲氧基化产物的对映体对通过c.s.p.-h.p.l.c.分离。结果表明，对映体5S,6R-环氧化物和5S,6S-二氢二醇是所有三种大鼠肝脏微粒体制剂在12-MBA的K区域5,6-双键代谢过程中优先形成的主要对映体。光学纯的12-MBA 5S,6R-环氧化物主要在C(6)位（R中心）水合形成（5S,6S）/（5R,6R）对映体比例为97:3的12-MBA反式-5,6-二氢二醇。然而，光学纯的12-MBA 5R,6S-环氧化物在C(5)和C(6)位水合几乎相等，形成（5S,6S）/（5R,6R）对映体比例为57:43的12-MBA反式-5,6-二氢二醇。