Phytoalexins from Pinus strobus bark infected with pinewood nematode, bursaphelenchus xylophilus.

From the bark of Pinus strobus infected with pinewood nematode, Bursaphelenchus xylophilus, a stilbenoid 3-O-methyldihydropinosylvin and a flavanone (2S)-pinocembrin were isolated as active principles of inducibly produced antifungal compounds. The structures of the compounds were determined on the basis of spectroscopic analyses. Close investigations of spectroscopic analyses led to the complete assignment of 13C NMR and 1H NMR chemical shifts for the former compound and to the determination of the stereochemistry of the latter compound from P. strobus to be 2S. Furthermore, the distribution and time course accumulation of the identified compounds were investigated. The former compound was demonstrated to be nematocidal and the concentrations of the compound in the inoculated branches were sufficient enough to inactivate the pinewood nematode within one week after inoculation.