7-Oxoorobanchyl Acetate and 7-Oxoorobanchol as Germination Stimulants for Root Parasitic Plants from Flax (Linum usitatissimum)

Abstract

Germination stimulants for root parasitic plants produced by flax (Linum usitatissimum L.) were purified and characterized. The root exudate of flax contained at least 8 active fractions, and liquid chromatography-tandem mass spectrometry (LC–MS/MS) and gas chromatography mass spectrometry (GC–MS) analyses suggested that there were 6 strigolactones. Two of them were identified as orobanchol and orobanchyl acetate by comparing NMR and GC–MS and LC–MS/MS data with those of synthetic standards. One of the two novel strigolactones was purified and determined as 7-oxoorobanchyl acetate [((3aS,4S,8bS,E)-8,8-dimethyl-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yloxy)methylene)-2,7-dioxo-3,3a,4,5,6,7,8,8b-octahydro-2H-indeno[1,2-b]furan-4-yl acetate) by 1D and 2D NMR spectroscopic, and ESI– and EI–MS spectrometric analyses. The other one was also purified and identified as 7-oxoorobanchol. The remaining two compounds could not been characterized due to their scarcity.