Biochemical Studies on Relationships between Plant Fungitoxins and Phytopathogens

通过对羽扇豆(Lupinus Albus)和黄羽扇豆(L.luteus)中组成异黄酮类化合物的研究，发现它们中含有大量简单和复杂的异黄酮类和香豆素类化合物，其中许多是真菌毒性的。羽扇豆异黄酮类化合物的结构变化是由以下五个因素引起的：1)基本结构(4种简单的异黄酮类)2)亚丙基(=3，3-二甲基烯丙基)取代6和/或3‘(白羽羽扇豆属)和6或8(黄羽羽扇豆属)3)戊烯基侧链的修饰(水合、末端羟基化和转化为2-羟基-3-甲基-3-丁烯基)4)环形成(二氢呋喃-，二氢吡喃和/或吡喃融合的A-和/或B-环)5-O-甲基化(L.luteus)长期以来，人们一直认为一些真菌具有代谢和解毒异黄酮类化合物的能力，在某些情况下，这一过程似乎与致病性密切相关。灰霉病菌能将异黄酮烯基化成各种二氢呋喃和二氢吡喃异黄酮以及二醇，所有这些都可能通过不饱和侧链在适当底物上的环氧化作用而产生。阐明了在非手性异黄酮向手性异黄酮的代谢中，产生真菌毒性大大降低的极性化合物的真菌代谢的底物专一性和立体化学。进一步的实验证实了环氧化物的存在作为从戊烯基异黄酮到环醚和乙二醇衍生物的代谢中间体。以灰霉病菌和5，2‘，4’-三羟基-7-甲氧基-8-戊烯基异黄酮为底物，成功地检测到了预期的环氧化物。从比较生化的角度考察了5，7，2‘，4’-四羟基-6-戊烯基异黄酮(叶黄酮)在大鼠肝脏匀浆中的去向。

As the results of the present study on constitutive isoflavonoids in lupins (Lupinus albus and L. luteus) were found to contain numerous simple and complex isoflavones and coumaronochromones, many of which were fungitoxic. The structural variation in the lupin isoflavonoids are due to the following five factors:1) basic structure (4 kinds of simple isoflavonoids)2) prenyl (=3,3-dimethylallyl) substitution at 6 and/or 3'(L. albus) and at 6 or 8 (L. luteus)3) modification of the prenyl sidechain (hydration, terminal hydroxylation and transformation to 2-hydroxy-3-methyl-3-butenyl group)4) ring formation (dihydrofurano-, dihydropyrano- and pyrano-fused A- and/or B-ring5) 5-O-methylation (L. luteus)It has long been recognized that some fungi have the ability to metabolise and detoxify isoflavonoids, and in certain cases this process seems to be closely linked with pathogenicity. Botrytis cinerea was found to convert prenylated isoflavones into various dihydrofurano- and dihydropyrano-isoflavones, and glycols, all of which might arise via epoxidation of the unsaturated sidechain in the appropriate substrate. The substrate specificity of the fungal metabolism yielding those polar compounds with greatly decreased fungitoxicity and stereochemistry in the metabolism of an achiral isoflavone to a chiral one been elucidated.A further experiment was conducted to confirm the presence of an epoxide as a metabolic intermediate from a prenylated isoflavone to cyclic ether and glycol derivatives. The expected epoxide was successfully detected by using B. cinerea and 5,2',4'-trihydroxy-7 methoxy-8-prenylisoflavone as a substrate.The fate of 5,7,2',4'-tetrahydroxy-6-prenylisoflavone (luteone) in rat liver homogenates was also examined from the interest in comparative biochemistry of the prenylated isoflavone metabolism.