Fry J R, Fentem J H, Salim A, Tang S P, Garle M J, Whiting D A
Department of Physiology and Pharmacology, University of Nottingham, UK.
J Pharm Pharmacol. 1993 Mar;45(3):166-70. doi: 10.1111/j.2042-7158.1993.tb05526.x.
The interaction of glutathione (GSH) with coumarin, or one of a series of compounds related to coumarin, was assessed in the absence and presence of liver microsomes (direct reaction and indirect reaction, respectively) to determine the structural requirements for direct and mono-oxygenase-mediated reaction of cyclic alpha,beta-unsaturated carbonyls with GSH. Acrolein was used as a positive control for the direct reaction, and produced complete or nearly complete depletion of GSH under all assay conditions. 5,6-Dihydro-2H-pyran-2-one and 2-cyclohexen-1-one also produced substantial depletion of GSH in the direct reaction, which was not increased by the addition of liver microsomes. Coumarin, 2H-pyran-2-one and precocene I (a substituted pyran lacking the 2-one structure) were not substrates for the direct reaction but did cause depletion of GSH when incubated in the presence of rat or human liver microsomes. These depletions were dependent on a functioning mono-oxygenase system as judged by the effects of omission of cofactors, addition of competitive or inactivating inhibitors of cytochrome P450, and induction. Dihydrocoumarin, delta-valerolactone, cyclohexanone and 4H-pyran-4-one were not substrates for either the direct or indirect reaction. These findings are rationalized on the basis of a direct nucleophilic attack of GSH on the alpha,beta-centre of the alpha,beta-unsaturated carbonyl compounds, which is hindered by benzenoid resonance in coumarin and 2H-pyran-2-one, for which enzyme-mediated reaction with GSH, probably via a 3,4-epoxide, is the favoured mechanism.
在不存在和存在肝微粒体的情况下（分别为直接反应和间接反应），评估了谷胱甘肽（GSH）与香豆素或一系列与香豆素相关的化合物之一的相互作用，以确定环状α,β-不饱和羰基与GSH直接反应和单加氧酶介导反应的结构要求。丙烯醛用作直接反应的阳性对照，在所有测定条件下均使GSH完全或几乎完全耗尽。5,6-二氢-2H-吡喃-2-酮和2-环己烯-1-酮在直接反应中也使GSH大量耗尽，添加肝微粒体后并未增加。香豆素、2H-吡喃-2-酮和早熟素I（一种缺乏2-酮结构的取代吡喃）不是直接反应的底物，但在大鼠或人肝微粒体存在下孵育时会导致GSH耗尽。根据辅因子缺失、细胞色素P450竞争性或失活抑制剂的添加以及诱导的影响判断，这些耗尽依赖于正常运行的单加氧酶系统。二氢香豆素、δ-戊内酯、环己酮和4H-吡喃-4-酮既不是直接反应也不是间接反应的底物。基于GSH对α,β-不饱和羰基化合物的α,β-中心的直接亲核攻击对这些发现进行了合理化解释，香豆素和2H-吡喃-2-酮中的苯环共振阻碍了这种攻击，对于它们来说，与GSH的酶介导反应可能通过3,4-环氧化物是更有利的机制。
