Abstract:

【Objective】 The activity of fraction 8 from the petroleum ether extract of Pharbitis purpurea seeds was investigated against Tetranychus cinnabarinus. 【Method】 The acaricidic activity of fraction 8 was measured with the methods of slide dip and leaf residue, and several enzymes in T. cinnabarinus treated with isolation fraction 8 were examined. The ultrastructure of the treated mites was observed by using transmission electron microscope (TEM). 【Result】 The tested fraction showed lethal effects on the mite adults and eggs with the LC50s of 0.4686 and 1.2212 mg/ml and the LC90s of 2.5935 and 3.1234 mg/ml, respectively. Glutathione-S-transferase activity was strongly induced in treated mites whereas acetylcholinease, monoamine oxidase and Ca2+-ATPase were suppressed in activity after treatment. The results indicated that the extracted fraction of P. purpurea seeds was acaricidal, perhaps attributing to neural transmit block in treated mites. TEM observations revealed that the treated mites suffered from the ruptures of cuticle, muscular filament, nuclear membrane, mitochondria and endoplasmic reticulum. 【Conclusion】 Thus, P. purpurea seeds can be exploited as new resources for developing potential acaricides.

Key words: Pharbitis purpurea, Tetranychus cinnabarinus, glutathione-S-transferase, acetylcholinease, monoamine oxidase, Ca2+-ATPase, transmission electron microscope