Biochemical Studies on Relationships between Plant Fungitoxins and Phytopathogens

点击翻译按钮获取中文摘要

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.