Nematicidal activity of compounds extracted from medicinal plants against the pine wood nematode Bursaphelenchus xylophilus

To investigate in vitro nematicidal activity against the pine wood nematode, Bursaphelenchus xylophilus, plant methanolic extracts were obtained from 26 medicinal plants and herbs in Vietnam. Of the plant extracts tested, a 10 mg ml(-1) concentration of Cinnamomum cassia bark extract showed the highest level of nematicidal activity against juvenile and adult B. xylophilus after treatment for 7 h. The remainder of the plant extracts had little or no effect on juveniles or adults. Four solvents, n-hexane, chloroform, ethyl acetate and n-butanol, were used initially to partition the compounds obtained from C. cassia extracts. The compound (5 mg ml(-1)) in the n-hexane fraction showed the highest nematicidal activity at 60 min after treatment. Compounds III and IV were then separated from the n-hexane fraction using silica gel plates. These compounds showed very similar activity against the pine wood nematode. However, treatment with different concentrations of these compounds resulted in a significant difference in their effects on the mortality of the pine wood nematode, with greater concentrations leading to increased mortality after the same exposure time. Overall, treatment with 3 mg ml(-1) of compounds III and IV resulted in greater than 95% mortality against juvenile and adult B. xylophilus at 50 min after treatment.