Enzymology and Stereochemistry in Lignan Biosynthesis

木脂素的生物合成还不是很清楚。特定木脂素的比旋转值可能因植物种类而异。木脂素和木质素之间的生物合成差异尚不清楚。花椒中呋喃木脂素[如(-)-松脂醇]的绝对构型为(8S，8‘S)。目前还没有关于(8S，8‘S)木脂素的生物合成研究。有趣的是，植物中的(-)-二异落叶松脂醇的构型是相反的，(8R，8‘R)，尽管它必须来自非天然的(+)-(8R，8’R)-松脂醇。为了研究花椒木脂素的生物合成和立体化学，以花椒和五味子花椒为材料，进行了饲喂实验和粗酶反应。主要研究结果如下：(1)制备了木脂素类化合物和[8-^&lt；14&gt；C]针叶醇(CA)，并将其作为正品和底物。(2)建立了高效液相色谱分析条件。(3)用[8-^&lt；14&gt；C]CA处理切段植株3h，结果…在本实验条件下，更多的是转化为松脂醇，而不是表儿松脂酚、芝麻素或细辛素。加入落叶松脂醇和次异落叶松脂醇的研究正在进行中。(4)在NADPH存在下，(&lt；+-)-松脂醇与植物的无细胞提取物孵育后形成(+)-落叶松脂醇。在NADPH和H_2O_2存在下，[8-^&lt；14&gt；C]CA与相同的提取物孵育后形成(+)-松脂醇、(+)-松脂醇和(-)-松脂醇，但(+)-形式的消耗很小。消耗的量与(+)-落叶松脂醇的量相似。结果表明，CA转变为(-lt；+--)-松脂醇，(+)-形式还原为(+)-落叶松脂醇。该构型与(-)-二异落叶松脂醇的构型相同。但(-)-二异落叶松脂醇的形成尚未发现。残留的松脂醇可能会有自然的(-)-征。(5)[8-^&lt；14&gt；C]CA在无辅因子存在的情况下与同一茎段的不溶性残渣孵育，得到(&lt；+&gt；)-松脂醇。这种形成可能是由细胞壁结合的漆酶催化的。当添加NAD和苹果酸时，(+)和(-)形式的比例为46.5：53.5。需要进一步的研究才能知道(-)-松脂醇是否由不溶性残留物直接生成。较少

The biosynthesis of lignans is not well-known. The value of specific rotation of a particular lignan may vary with the plant species. The biosynthetic difference between lignans and lignins is unclear. Absolute configuration of furofuran lignans [e.g. (-) -pinoresinol] in Zanthoxylum ailanthoides is (8S,8'S). There is no biosynthetic study on the (8S,8'S) lignans. Interestingly, the configuration of (-) -secoisolariciresinol in the plant is opposite, (8R,8'R), although it must be derived from unnatural (+) - (8R,8'R) -pinoresinol. To investigate biosynthesis and stereochemistry in Zanthoxylum lignans, feeding experiments and crude enzyme reactions were performed using shoots of Z.ailanthoides and Z.schinifolium. following results were obtained.(1) Lignans and [8-^<14>C] coniferyl alcohol (CA) were prepared and used as authentic compounds and substrates. (2) Analytical conditions by HPLC were established. (3) Administration of [8-^<14>C] CA to excised shoots of the plants for 3 h result … More ed in conversion into pinoresinol, not into epipinoresinol, sesamin or asarinin in this experimental condition. Incorporation into lariciresinol and secoisolariciresinol is under study. (4) Incubation of (<plus-minus>) -pinoresinol with cell-free extracts of the plants in the presence of NADPH showed formation of (+) -lariciresinol. Incubation of [8-^<14>C] CA with the same extracts in the presence of NADPH and H_2O_2 showed formation of (+) -larisiresinol and (+) and (-) -pinoresinol with the small depletion of (+) -form. The amount of the depletion is similar to that of the (+) -lariciresinol. It was concluded that CA was transformed to (<plus-minus>) -pinoresinol, (+) -form of which was reduced to (+) -lariciresinol. This configuration is the same as that of (-) -secoisolariciresinol. But (-) -secoisolariciresinol formation have not found yet. Residual pinoresinol might have the natural (-) -sign. (5) Incubation of [8-^<14>C] CA with the insoluble residue from the same stems in the absence of cofactors gave (<plus-minus>) -pinoresinol. This formation might be catalyzed by a cell wall bound laccase. When NAD and malate were supplied, the ratio of (+) and (-) forms was 46.5 : 53.5. Further study is necessary to know whether direct formation of (-) -pinoresinol occurred by the insoluble residue. Less