Accumulation of apocarotenoids in mycorrhizal roots of Ornithogalum umbellatum.

Colonization of roots of Ornithogalum umbellatum by the arbuscular mycorrhizal fungus Glomus intraradices induced the accumulation of different types of apocarotenoids. In addition to the mycorrhiza-specific occurrence of cyclohexenone derivatives and the "yellow pigment" described earlier, free mycorradicin and numerous mycorradicin derivatives were detected in a complex apocarotenoid mixture for the first time. From the accumulation pattern of the mycorradicin derivatives their possible integration into the continuously accumulating "yellow pigment" is suggested. Structure analyses of the cyclohexenone derivatives by MS and NMR revealed that they are mono-, di- and branched triglycosides of blumenol C, 13-hydroxyblumenol C, and 13-nor-5-carboxy-blumenol C, some of which contain terminal rhamnose as sugar moiety.