Fungal Transformation of the Antifungal Isoflavone Luteone Satoshi Tahara, Shiro Nakahara, Junya Mizutani and John L
Agric. Biol. Chem., 48 (6), 1471 ~ 1477, 1984 1471 Fungal Transformation of the Antifungal Isoflavone Luteone Satoshi Tahara, Shiro Nakahara, Junya Mizutani and John L. Ingham* Department of Agricultural Chemistry, Faculty of Agriculture, Hokkaido University, Kita-ku, Sapporo 060, Japan *Phytochemical Unit, Department of Botany, University of Reading, Whiteknights, Reading RG6 2AS, England Received November 4, 1983 An antifungal isoflavone, luteone [5,7,2/,4/-tetrahydroxy-6-(3,3-diniethylallyl)isoflavone] is metabolised by cultures of Aspergillus flavus and Botrytis cinerea into 2",3"-dihydro-3"- hydroxyluteone (AF- 1), 2//,3 '/-dihydrodihydroxyluteone, a dihydrofuranoisoflavone (BG-1) and a dihydropyranoisoflavone. The structures of the metabolites were elucidated by physico-chemical and chemical procedures. The major metabolites, AF-1 and BC-1 are much less toxic than luteone against Cladosporium herbarum. The possible metabolic pathways are briefly discussed. SJ^^'-Tetrahydroxy^-^B-dimethyl- demethylating or reducing the molecule.6'7* allyl)isoflavone (luteone, 1) was first isolated In the case of 5,7,2',4'-tetrahydroxy-8-(3,3- from the young fruits of Lupinus luteus L. dimethylallyl)isoflavanone (kievitone) and 3,9- (yellow lupin) and found to be strongly dihydroxy- 1 0-(3, 3-dimethylallyl)pterocarpan antifungal.1) Considerable quantities of 1 and (phaseollidin), it was found that metabolism the related fungitoxin 5,7,4'-trihydroxy-6- by Fusalium solani f. sp. phaseoli involved a (3,3-dimethylallyl)isoflavone (wighteone) also straightforward hydration of the sidechain to occur on the surface of lupin Ieaves2'3) where, yield kievitone hydrate8) and phaseollidin hy- in conjunction with other isoflavones [e.g. drate,9* respectively.
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