Studies on Fungal Metabolism of Phytoalexins

以异戊烯化异戊烯酮及其相关化合物为底物，以灰葡萄孢和黄曲霉为底物，研究了植物抗毒素的真菌代谢。研究结果总结如下。(1)7-O-甲基-叶黄素（1）和7-O-甲基-2，3-脱氢酮酮（2）是从相应的丁香酮、从Lupinus luteus中分离的topazolin（3）和从Piscidia erythrina根皮中分离的piscidone的化学衍生物。6-异戊烯化的黄酮3被代谢为6-异戊烯化的黄酮。化合物4中C-6'位的异戊烯基被B成功地转化为相应的环醚。灰叶(2)化合物1的主要代谢产物为右旋2，2-二甲基-3-羟基吡喃糖苷。立体化学估计为S-构型。(3)化合物2不被A. flavus，但由B。在异戊二烯基侧链中的双键处产生环氧衍生物和二醇。后一种代谢产物显示为S-异构体，环氧化物的酸水解产物（立体保留）与S-异构体一致。因此，环氧中间体的构型被证实为S。因此，首次证实了在异戊二烯化化合物代谢成二氢呋喃基或二氢吡喃基环醚和/或2，3-二氢二羟基异戊二烯基衍生物中存在环氧中间体。albus）进行了精确的检测，并且复合羽扇豆酮的结构表明它们可能是由异戊二烯化的羽扇豆酮通过环氧中间体产生的。因此，羽扇豆酮的生物合成与真菌代谢密切相关。

Fungal metabolism of phytoalexins was investigated by using prenylated isoflavones and related compounds as substrates, and Botrytis cinerea and Aspergillus flavus. Research results are summarized as follows. (1) 7-O-Methyl-luteone (1) and 7-O-Methyl-2,3-dehydrokievitone (2) both chemically derivated from the corresponding isoflavones, topazolin (3) isolated from Lupinus luteus and piscidone from the root barks of Piscidia erythrina were metabolized by two fungi. A 6-prenylated flavone 3 was metabolized as 6-prenylated isoflavone had been. The prenyl group at C-6' in 4 was successfully transformed into the corresponding cyclic ether by B. cinerea. (2) The major metabolite from 1 was confirmed to be 2,2-dimethyl-3-hydroxypyranoisoflavone with dextrorotatory nature. The stereochemistry was estimated to be S-configuration. (3) Compound 2 was rapidly metabolized not by A. flavus, but by B. cinerea to yield an epoxy-derivative at the double bond in the prenyl side chain and a glycol. The latter metabolite revealed to be S-isomer with which the acid hydrolyzate (stereo-retention) of the epoxide agreed well. Therefore the configuration of the epoxy-intermediate was confirmed to be S. The presence of an epoxy-intermediate in the metabolism of a prenylated compound into a dihydrofurano- or dihydropyrano-cyclic ether and/or a 2,3-dihydrodihydroxy- prenyl derivative was thus confirmed for the first time.Isoflavonoidal constituents in white lupin (L. albus) were precisely examined and the structures of complex lupin isoflavones suggested that they were presumably produced from prenylated isoflavones via epoxy-intermediates. The biogenedis for lupin isoflavones was thus closely related to their fungal metabolism.