Abstract: Peganum harmala L. is a resistant plant distributed in the desert area of China. The rising intensity of moisture, level of resinosis and index of disease of pine infected by mixed instar of Bursaphelenchus xylophilus were not significantly different from CK when pine branch were treated with 250 ?g?ml-1 of n-butanol extract of P. harmala in water-potted test, which indicated n-butanol extract of P. harmala shows control effects superior to petroleum ether, chloroform and water extract against B. xylophilus. The total alkaloid extract, harmaline, harmine and 8 fractions named A1-A8 were obtained from n-butanol extract. Result of these fractions' nematocidal toxicity test showed that harmaline, fraction A1 and A6 would be the main nematocidal components of P. harmala, their values of LC50 were 135.74,160.40 and 86.02 ?g?ml-1 after 48 h against mixed instar B. xylophilus, respectively. The n-butanol extract, total alkaloid, harmaline, harmine, fraction A1 and A6 all could not significantly inhibited the activities of aldaline phoisphatase, but AChE and acid phosphatase in vivo. After 6 h when mixed instar of B. xylophilus were treated at the concentration of 100 ?g?ml-1, the activities of AChE and acid phosphatase were inhibited by 50.15%-73.14% and 38.56%-48.37%, respectively. The inhibition rate of α-carboxylesterase activity were 39.78%, 33.80%, 34.85% and 54.22% after 12 h treated with total alkaloid extract, harmaline, harmine and fraction A1 at concentration of 100 ?g?ml-1. However, n-butanol extract, harmine and fraction A1 significantly suppressed the activity of β-carboxylesterase than other extracts, the inhibition rate of activity got 42.79%, 33.66% and 30.02%, respectively after 12 h treated at the same concentration of 100 ?g?ml-1. Based on these experimental results, it is inferred that one of the nematocidal mode of action may inhibit the activity of AChE for P. harmala extract. More researches are needed on nematocidal components of P. harmala to search the main active compounds and develop some new kinds of biorational nematocide.

Key words: Peganum harmala, Secondary metabolites, Bursaphelenchus xylophilus, Bioactivities, Physiological effects