Kulling S E, Honig D M, Simat T J, Metzler M
Institute of Food Chemistry, University of Karlsruhe, P.O. Box 6980, D-76128 Karlsruhe, Germany.
J Agric Food Chem. 2000 Oct;48(10):4963-72. doi: 10.1021/jf000524i.
The oxidative metabolism of the major soy isoflavones daidzein and genistein was investigated using liver microsomes from Aroclor-treated male Wistar rats. Both daidzein and genistein were extensively metabolized and are therefore excellent substrates for cytochrome P450 enzymes. The identity of the metabolites was elucidated using high-performance liquid chromatography (HPLC) with diode array detection, gas chromatography-mass spectrometry (GC/MS), and HPLC/atmospheric pressure ionization electrospray mass spectrometry (API-ES MS) as well as reference substances. Daidzein was converted to nine metabolites, comprising four monohydroxylated, four dihydroxylated, and one trihydroxylated metabolite. Genistein was metabolized to four monohydroxylated and two dihydroxylated products. With both isoflavones the additional hydroxy groups are exclusively introduced into the ortho positions of existing phenolic hydroxy groups. The major metabolites of daidzein were identified as 6,7,4'-trihydroxyisoflavone, 6,7,3',4'-tetrahydroxyisoflavone, 7,8, 4'-trihydroxyisoflavone, and 5,6,7,4'-tetrahydroxyisoflavone. The main microsomal metabolites of genistein were 5,6,7, 4'-tetrahydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone. Furthermore, the GC/MS and HPLC/API-ES MS analysis support the conclusion that one monohydroxylated metabolite of daidzein and genistein is hydroxylated at the aliphatic position C-2 of the C-ring. The UV-vis, GC/MS, and HPLC/MS data of all detected metabolites as well as the derived chemical structure of the metabolites are presented. Most metabolites are reported in this paper for the first time. On the basis of these findings it is suggested that hydroxylation reactions may also play an important role in the in vivo metabolism of the soy isoflavones daidzein and genistein.
利用经多氯联苯混合物（Aroclor）处理的雄性Wistar大鼠的肝脏微粒体，对大豆主要异黄酮黄豆苷元和染料木黄酮的氧化代谢进行了研究。黄豆苷元和染料木黄酮均被广泛代谢，因此是细胞色素P450酶的优良底物。使用配备二极管阵列检测的高效液相色谱（HPLC）、气相色谱 - 质谱联用仪（GC/MS）以及HPLC/大气压电离电喷雾质谱仪（API-ES MS）并结合参考物质来阐明代谢产物的身份。黄豆苷元被转化为九种代谢产物，包括四种单羟基化、四种二羟基化和一种三羟基化代谢产物。染料木黄酮被代谢为四种单羟基化和两种二羟基化产物。对于这两种异黄酮，额外的羟基仅被引入到现有酚羟基的邻位。黄豆苷元的主要代谢产物被鉴定为6,7,4'-三羟基异黄酮、6,7,3',4'-四羟基异黄酮、7,8,4'-三羟基异黄酮和5,6,7,4'-四羟基异黄酮。染料木黄酮的主要微粒体代谢产物是5,6,7,4'-四羟基异黄酮和5,7,8,4'-四羟基异黄酮。此外，GC/MS和HPLC/API-ES MS分析支持了这样的结论，即黄豆苷元和染料木黄酮的一种单羟基化代谢产物在C环的脂肪族位置C-2处被羟基化。呈现了所有检测到的代谢产物的紫外可见光谱、GC/MS和HPLC/MS数据以及代谢产物的推导化学结构。本文中报道的大多数代谢产物均为首次发现。基于这些发现，有人提出羟基化反应在大豆异黄酮黄豆苷元和染料木黄酮的体内代谢中可能也起着重要作用。
