Accumulation of apocarotenoids in mycorrhizal roots of leek (Allium porrum)

Colonization of the roots of leek (Allium porrum L.) by the arbuscular mycorrhizal fungus Glomus intraradices induced the formation of apocarotenoids, whose accumulation has been studied over a period of 25 weeks. Whereas the increase in the levels of the dominating cyclohexenone derivatives resembles the enhancement of root length colonization, the content of mycorradicin derivatives remains relatively low throughout. Structural analysis of the cyclohexenone derivatives by mass spectrometry and NMR spectroscopy showed that they are mono- and diglycosides of 13-hydroxyblumenol C and blumenol C acylated with 3-hydroxy-3-methyl-glutaric and/or malonic acid. Along with the isolation of three known compounds five others are shown to be hitherto unknown members of the fast-growing family of mycorrhiza-induced cyclohexenone conjugates.