title: Conifer flavonoid compounds inhibit detoxification enzymes and synergize insecticides.
abstract: Detoxification by glutathione S-transferases (GSTs) and esterases are important mechanisms associated with insecticide resistance. Discovery of novel GST and esterase inhibitors from phytochemicals could provide potential new insecticide synergists. Conifer tree species contain flavonoids, such as taxifolin, that inhibit in vitro GST activity. The objectives were to test the relative effectiveness of taxifolin as an enzyme inhibitor and as an insecticide synergist in combination with the organophosphorous insecticide, Guthion (50% azinphos-methyl), and the botanical insecticide, pyrethrum, using an insecticide-resistant Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) strain. Both taxifolin and its isomer, quercetin, increased the mortality of 1(st) instar CPB larvae after 48h when combined with Guthion, but not pyrethrum. Taxifolin had greater in vitro esterase inhibition compared with the commonly used esterase inhibitor, S, S, S-tributyl phosphorotrithioate (DEF). An in vivo esterase and GST inhibition effect after ingestion of taxifolin was measured, however DEF caused a greater suppression of esterase activity. This study demonstrated that flavonoid compounds have both in vitro and in vivo esterase inhibition, which is likely responsible for the insecticide synergism observed in insecticide-resistant CPB.
authors.affiliation: College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China; Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario N5V 4T3, Canada.
authors.forename: Zhiling
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario N5V 4T3, Canada.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Biology, University of Ottawa, Ontario K1N 6N5, Canada.
authors.forename: Suqi
authors.initials: S
authors.lastname: Liu
authors.affiliation: College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: weiqin@nwsuaf.edu.cn.
authors.forename: Qin
authors.initials: Q
authors.lastname: Wei
authors.affiliation: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario N5V 4T3, Canada. Electronic address: ian.scott@agr.gc.ca.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Scott
mesh_terms: D000818:Animals; D001517:Coleoptera; D004950:Esterases / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000378:metabolism*; D007306:Insecticides / Q000378:metabolism*; D064028:Tracheophyta / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D007306:Insecticides; D005982:Glutathione Transferase; D004950:Esterases
keywords: Azinphos-methyl; Colorado potato beetle; Esterase; Glutathione S-transferase; Pyrethrum; Taxifolin