Abstract

1. Nabumetone (NAB) is a non-steroidal anti-inflammatory drug used clinically, and its biotransformation includes the major active metabolite 6-methoxy-2-naphthylacetic acid (6-MNA). One of the key intermediates between NAB and 6-MNA may be 3-hydroxy nabumetone (3-OH-NAB).

2. The aim of the present study was to investigate the role of flavin-containing monooxygenase (FMO) isoform 5 in the formation of 6-MNA from 3-OH-NAB. To elucidate the biotransformation of 3-OH-NAB to 6-MNA, an authentic standard of 3-OH-NAB was synthesised and used as a substrate in an incubation with human liver samples or recombinant enzymes.

3. The formation of 3-OH-NAB was observed after the incubation of NAB with various cytochrome P450 (CYP) isoforms. However, 6-MNA itself was rarely detected from NAB and 3-OH-NAB. Further experiments revealed a 6-MNA peak derived from 3-OH-NAB in human hepatocytes. 6-MNA was also detected in the extract obtained from 3-OH-NAB by a combined incubation of recombinant human FMO5 and human liver S9.

4. We herein demonstrated that the reaction involves carbon-carbon cleavage catalyzed by the Baeyer–Villiger oxidation (BVO) of a carbonyl compound, the BVO substrate, such as a ketol, by FMO5. Further in vitro inhibition experiments showed that multiple non-CYP enzymes are involved in the formation of 6-MNA from 3-OH-NAB.

摘要

1. 萘丁美酮（NAB）是临床上使用的非甾体类抗炎药，其生物转化包括主要的活性代谢物6-甲氧基-2-萘乙酸（6-MNA）。NAB和6-MNA之间的关键中间体之一可能是3-羟基萘丁美酮（3-OH-NAB）。

2. 本研究的目的是研究含黄素的单加氧酶（FMO）同工型5在由3-OH-NAB形成6-MNA中的作用。为了阐明3-OH-NAB向6-MNA的生物转化，合成了一种真实的3-OH-NAB标准品，并将其用作与人肝样品或重组酶孵育的底物。

3. 将NAB与各种细胞色素P450（CYP）同工型孵育后，观察到3-OH-NAB的形成。但是，很少从NAB和3-OH-NAB中检测到6-MNA本身。进一步的实验揭示了人肝细胞中源自3-OH-NAB的6-MNA峰。通过重组人FMO5和人肝S9的组合孵育，在从3-OH-NAB获得的提取物中也检测到6-MNA。

4. 我们在本文中证明了该反应涉及通过FMO5催化的羰基化合物的Baeyer-Villiger氧化（BVO）催化的碳-碳裂解，BVO底物（如酮醇）。进一步的体外抑制实验表明，多种非CYP酶参与了从3-OH-NAB形成6-MNA的过程。