Pest management science | 2019
Synthesis of thymyl esters and their insecticidal activity against Spodoptera litura (Lepidoptera: Noctuidae).
Abstract
BACKGROUND\nThymol, a natural phenolic monoterpene originating from Thymus vulgaris, is recognized as a safe and potent botanical insecticide to many insects. The structural modification of thymol into thymyl esters is a potential approach for the development of novel insecticides, which showed more toxicity than thymol. However, there are no reports on the insecticidal activity of thymyl esters to control Spodoptera litura.\n\n\nRESULTS\nThymol was structurally modified into ten thymyl esters by esterification using a new reagent, PPh3 /Br3 CSO2 Ph. The insecticidal activity of these compounds was examined against the second instars of Spodoptera litura using a topical application. Among the ten thymyl esters evaluated, thymyl cinnamate was the most toxic with LD50 \xa0=\xa00.41 and 0.34\u2009μg/larva after 24 and 48\u2009h posttreatment, respectively. In addition, thymyl cinnamate-treated larvae showed increasing carboxylesterase and acetylcholinesterase activities in vivo experiment, whereas glutathione S-transferase activity showed no significant difference.\n\n\nCONCLUSION\nThymyl cinnamate were first reported to exhibit toxicity against S. litura 2.41-2.46 fold more efficient than thymol. However, the detailed biochemical interactions are necessary for further development of novel insecticides. This article is protected by copyright. All rights reserved.