INDUCED FORMATION OF DIHYDROPHENANTHRENES AND BIBENZYL SYNTHASE UPON DESTRUCTION OF ORCHID MYCORRHIZA

Increasing amounts of 1,7-dihydroxy-5-methoxy-9,10-dihydrophenanthrene and 3,3'-dihydroxy-5,4'-dimethoxybibenzyl were formed in rhizomes of the orchid Epipactis palustris after wounding. The induced formation of these compounds depended on wounding and the extent of fungal infection present within the rhizome. In a similar way, the activity of a bibenzyl synthase converting m-hydroxyphenylpropionyl-CoA and malonyl-CoA into 3,5,3'-trihydroxybibenzyl was induced. The enzyme exhibits molecular properties which indicate its relation to stilbene synthases but shows catalytic activities which prove its substrate preference of dihydrocinnamic acid derivatives to cinnamic acid derivatives.