Nematicidal activity of malabaricones isolated from Myristica malabarica fruit rinds against Bursaphelenchus xylophilus

Plant extracts from 50 plant species were tested for their nematicidal activities against Bursaphelenchus xylophilus, the causative agent of pine wilt disease. Out of 50 extracts, the methanol extract of Myristica malabarica fruit rinds showed the most potent nematicidal activity with mortality of 100% at a concentration of 1000 mu g ml(-1) against B. xylophilus. Three nematicidal substances were isolated by bioassay-guided fractionation and then identified as malabaricones A, B and C by mass and NMR spectral data. Both malabaricones B and C showed higher activity than malabaricone A. There was a significant synergistic interaction between the three compounds on the pine wood nematode. When the combination of three compounds at a ratio of 1 : 1 : 1 was applied, its EC50 value was 11.8 mu g ml(-1). These results indicate that the extract of M. malabarica containing the three resorcinols could be useful as a natural nematicide for the control of pine wilt disease.