抄録
Cucumber (Cucumis sativus) plants were found to exude at least 12 germination stimulants for root parasitic weeds including 5 known strigolactones, 7-oxoorobanchol, 7-oxoorobanchyl acetate, orobanchol, orobanchyl acetate, and 4-deoxyorobanchol. Two novel germination stimulants were purified from cucumber root exudates and their structures were determined to be 7α- and 7β-hydroxyorobanchyl acetate by 1D and 2D NMR spectroscopy, and ESI- and EI-MS spectrometry. The stereochemistry was determined by NOE measurement and by comparing the CD spectra with those of the synthetic standards of four stereoisomers of orobanchol. 7α- and 7β-Hydroxyorobanchol were detected by LC-MS/MS, and GC-MS analysis of purified sample confirmed their structures. The germination stimulation activities of 7α- and 7β-hydroxyorobanchyl acetate on Orobanche minor were comparable to those of orobanchyl acetate and 7-oxoorobanchyl acetate. By contrast, 7β-hydroxyorobanchyl acetate was a highly potent germination stimulant for Phelipanche ramosa inducing more than 50% germination at 10 pM.
