Essential oil of Chinese medicinal herb,Ligusticum chuanxiongdried rhizome was found to possess insecticidal activity against maize weevils, Sitophilus zeamais. The main components ofL. chuanxiongessential oil wereZ-3-butylidenephthalide (20.56%),Z-ligustilide (19.61%), 4-terpinenol (8.82%), 4-vinylguaiacol (6.81%) andα-selinene (6.01%). Bioactivity-guided chromatographic separation of the essential oil on repeated silica gel columns led to isolate three compounds namely

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... ligustilide and 4-vinylguaiacol.Z-liqustilide andZ-3-butylidenephthalide showed pronounced toxicity againstS. zeamais(LD50= 10.23 and 15.81 μg/adult respectively) and were more toxic than 4-vinylguaiacol (LD50= 63.75 μg/adult). The crude essential oil also possessed contact toxicity against S. zeamais (LD50= 13.09 μg/adult).