Abstract: To explore the insecticidal active constituents, toxic effects and toxicological mechanisms of Vitex negundo L. from Taishan Mountain, we investigated the insecticidal components of V. negundo weed seed extract utilizing silica gel column chromatography, GC-MS technology and biological activity tracking, and the toxicity and action mechanism of β-caryophyllene and α-pinene, isolated from V. negundo weed seed extract, against cotton aphid Aphis gossypii using bioassay and biochemical analysis. The results showed that β-caryophyllene and α-pinene with high toxic effect against A. gossypii were isolated from V. negundo weed seed extract by silica gel column chromatography repeatedly, with their contents as high as 7.68% and 5.45%, respectively. The contact toxicities of β-caryophyllene and α-pinene against A. gossypii were all obvious, and the higher one was β-caryophyllene whose LD₅₀ reached 0.65×10^-1 μg per individual. We also found strong repellent effect of β-caryophyllene and α-pinene against A. gossypii, with their AFC₅₀ values being 0.80×10³ and 0.89×10³ mg/L, respectively, 24 h after treatment. At the sublethal dose, they had significant adverse effects on the fertility, honeydew excretion frequency and honeydew production of the aphid. In vitro and in vivo conditions, β-caryophyllene and α-pinene distinctly inhibited the activities of acetylcholine esterase, polyphenol oxidase, carboxylesterase and glutathione S-tramsferases in A. gossypii. The results suggest that β-caryophyllene and α-pinene are important insecticidal compounds of V. negundo, and their action mechanisms show the characteristics of diversity. Therefore, they are worthy of further exploitation and application.

Key words: Vitex negundo, Aphis gossypii, β-caryophyllene, α-pinene, toxicity, action mechanism