Elucidation of biosyntheric mechanisms and metabolisms for lignans

为了阐明木脂素的生物合成机制，我们对几种植物中木脂素的形成进行了研究。首先，我们重点研究了厚朴中呋喃木脂素的形成。北极星。关于分离的木脂素的对映体成分。松香醇和丁香醇等酚性呋喃木脂素在光学上是不纯的。另一方面，非酚性呋喃木脂素如eudesmin、yangambin和kobusin是光学纯净的。这些结果表明，非酚性呋喃木脂素的形成是通过对映体选择性酶来实现的。此外，我们还考察了酚类呋喃木脂素与无细胞提取物的O-甲基化反应。北极星。结果表明，无细胞提取物催化松脂醇的O-甲基化反应，使松脂醇转化为丁香素，丁香酚转化为杨梅宾，体外转甲基反应具有对映选择性，(+)-构型为选择性底物。根据其木脂素的烯基组成，提出了由两个芥子醇分子通过非选择性偶联反应生成外消旋丁香树脂醇，然后以(+)-丁香脂醇为底物转化为丁香醇二葡萄糖苷。初步实验表明，在亚麻植物中存在一个有序的生物合成序列，最初涉及立体选择性偶联得到呋喃木脂素(+)-松脂酚，然后将其转化为四氢呋喃和二苯基丁烷骨架。

In order to clarify biosynthetic mechanism for lignans, we investigated the formation of lignans in several plant.First, we have focused our research efforts on the formation of furofuran lignans in magnolia kobus var. borealis. With respect to enantiomeric composition of isolated lignans from M. kobus var. borealis, phenolic furofuran lignans such as pinorersinol and syringaresinol were optically impure. On the other hand, non-phenolic furofuran lignans such as eudesmin, yangambin and kobusin were optically pure. these results suggested that enantioselective enzyme are in formation of the non-phenolic furofuran lignans. Also, we examined O-methlation reactions of phenolic furofuran lignans by incubation with cell-free extracts from M. kobus var. borealis. It was shown that the cell-free extracts catalyzed the O-methylation reactions of pinoresinol syringaresinol, suggesting the conversions of pinoresinol into eudesmin, and syringaresinol into yangambin, respectively, The in vitro transmethlation reactions observed were enantioselective with the (+)-forms being the preferred substrates.Next, we investigated lignan formation in Acanthopanax senticosus. Based on the enanyiomeric composition of their lignans, it was suggested that racemic syringaresinol formed from two molecules of sinapyl alcohol by a non-selective coupling followed by transformation into syringaresinol diglucoside with the (+)-syringaresinol being the preferred substrate.In study of lignans flax (Linum usitatissimum), it was shown that secoisolariciresinol diglucoside does not occur in flaxseed in a free form, but rather occurs in a complex ester. Preliminary experiments have indicated that in flax plant there is an orderly biosynthetic sequence initially involving stereoselective coupling to give the furofuran lignan(+)-pinoresinol, and its subsequent transformation into tetrahydrofuran and dibenzylbutane skeleta.