Insecticidal activities of methyleugenol and β-asarone, from the herbal medicines Saishin and Sekishokon, and other alkoxy-propenyl-benzene derivatives against the cigarette beetle Lasioderma serricorne (Coleoptera: Anobiidae)

The principal insecticidal compounds from the herbal medicines Saishin, the root of Asarum sieboldii Miquel, and SekishAikon, the rhizome of Acorus gramineus Soland, were isolated by successive silica gel column chromatography and high performance liquid chromatography. The active components, which work against larvae of the cigarette beetle, Lasioderma serricorne (F.), were identified as methyleugenol (4-allyl-1,2-dimethoxybenzene) and beta-asarone {1,2,4-trimethoxy-5-[(Z)-prop-1-enyl]benzene} by gas chromatography and gas chromatography/mass spectrometry analyses. These two compounds share some structural features, such as a benzene ring with o-dimethoxy groups and a propenyl group in the opposite position. Consequently, the insecticidal activities of 20 structurally related compounds were tested to evaluate their structure-activity relationship. We found myristicin (5-allyl-1-methoxy-2,3-methylenedioxybenzene) exhibited comparable insecticidal activity to methyleugenol and beta-asarone, but the other tested compounds were less active. The lack of insecticidal activity of compounds with a hydrogen, hydroxy, or acetoxy substituent in place of one methoxy group indicates that o-dimethoxy groups are essential for insecticidal activity. The position and configuration of a double bond in the propenyl side chain affected the toxicity, but there was a lack of consistency in the structure-activity relationship for this.