To study insecticidal mechanism of terpinen-4-ol, a main insecticidal composition in the essential oil of Sabina vulgaris, the 5th instar larvae of Mythimna separta, were investigated with terpinen-4-ol by topical application. The activities of phosphatase, glutathione S-transferase (GSTs), cytochrome P450 (P450), and polyphenol oxidase (PPO) of tested insects were determined in all poisoning stages, including exciting stage, convulsing stage, paralysis stage, and recover stage. The result showed that the activities of both acid phosphatase (ACP) and alkaline phosphatase (AKP) in treated insects were induced by terpinen-4-ol, but ACP was inhibited in paralysis stage. The activities of GSTs were inhibited in exciting stage, convulsing stage, and paralysis stage, but gradually recovered in recover stage. O-demethylase activity of cytochrome P450 was inhibited by terpinen-4-ol, and the inhibition rate in all poisoning stages were 26.27, 46.03, 80.24, and 90.22%, respectively. PPO activities were strongly inhibited by terpinen-4-ol both in vitro and in vivo. In conclusion, the activities of P450, GSTs, and PPO could have relation with toxicity of terpinen-4-ol against larvae of the Mythimna separta, but recover stage of the poisoning insects might be related to GSTs induced. As a new insecticide or synergist, terpinen- 4-ol has a potential value in field of insecticide resistance management.
MA Zhi-qing HAN Xiu-ling FENG Jun-tao LI Guang-ze ZHANG Xing
To reveal the insecticidal mechanism of terpinen-4-ol,the activity of Na+,K+-ATPase in insects tested were determined in vivo and in vitro.The results showed that terpinen-4-ol and its ester derivatives had strong contact activity to housefly and the contact toxicities of its derivatives except Z3 were all superior or equivalent to terpinen-4-ol.All the 7 compounds had strong inhibition towards activity of Na+,K+-ATPase.With poisoning symptom exacerbating,the inhibition rates were gradually increased.In vitro,the IC50 of terpinen-4-ol,Z1,Z2,Z4,Z5,and Z6 was 155.89,197.98,96.02,121.36,124.85,and 153.74 μg mL-1,respectively.There was well correlation between the LD50 of terpinen-4-ol derivatives to housefly and the IC50 of terpinen-4-ol derivatives to Na+,K+-ATPase in housefly.In conclusion,Na+,K+-ATPase was likely the target of terpinen-4-ol against insects.
