title: Inhibition of insect glutathione S-transferase (GST) by conifer extracts.
abstract: Insecticide synergists biochemically inhibit insect metabolic enzyme activity and are used both to increase the effectiveness of insecticides and as a diagnostic tool for resistance mechanisms. Considerable attention has been focused on identifying new synergists from phytochemicals with recognized biological activities, specifically enzyme inhibition. Jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP.), balsam fir (Abies balsamea (L.) Mill.), and tamarack larch (Larix laricina (Du Roi) Koch) have been used by native Canadians as traditional medicine, specifically for the anti-inflammatory and antioxidant properties based on enzyme inhibitory activity. To identify the potential allelochemicals with synergistic activity, ethanol crude extracts and methanol/water fractions were separated by Sephadex LH-20 chromatographic column and tested for in vitro glutathione S-transferase (GST) inhibition activity using insecticide-resistant Colorado potato beetle, Leptinotarsa decemlineata (Say) midgut and fat-body homogenate. The fractions showing similar activity were combined and analyzed by ultra pressure liquid chromatography-mass spectrometry. A lignan, (+)-lariciresinol 9'-p-coumarate, was identified from P. mariana cone extracts, and L. laricina and A. balsamea bark extracts. A flavonoid, taxifolin, was identified from P. mariana and P. banksiana cone extracts and L. laricina bark extracts. Both compounds inhibit GST activity with taxifolin showing greater activity compared to (+)-lariciresinol 9'-p-coumarate and the standard GST inhibitor, diethyl maleate. The results suggested that these compounds can be considered as potential new insecticide synergists.
authors.affiliation: College of Forestry, Northwest A&F University Yangling, Shaanxi, China; Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: Zhiling
authors.initials: Z
authors.lastname: Wang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zhao
authors.forename: Mamdouh M
authors.initials: MM
authors.lastname: Abou-Zaid
authors.forename: John T
authors.initials: JT
authors.lastname: Arnason
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Brendan
authors.initials: B
authors.lastname: Walshe-Roussel
authors.forename: Andrew
authors.initials: A
authors.lastname: Waye
authors.forename: Suqi
authors.initials: S
authors.lastname: Liu
authors.forename: Ammar
authors.initials: A
authors.lastname: Saleem
authors.forename: Luis A
authors.initials: LA
authors.lastname: Cáceres
authors.forename: Qin
authors.initials: Q
authors.lastname: Wei
authors.forename: Ian M
authors.initials: IM
authors.lastname: Scott
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000187:drug effects* / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D005216:Fat Body / Q000187:drug effects / Q000201:enzymology; D041981:Gastrointestinal Tract / Q000187:drug effects / Q000201:enzymology; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D007814:Larva / Q000187:drug effects; D017705:Lignans / Q000494:pharmacology; D010574:Pesticide Synergists; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D011794:Quercetin / Q000031:analogs & derivatives / Q000494:pharmacology; D064028:Tracheophyta / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D007306:Insecticides; D017705:Lignans; D010574:Pesticide Synergists; D010936:Plant Extracts; D011794:Quercetin; C003377:taxifolin; D005982:Glutathione Transferase
keywords: Abies balsamea; Colorado potato beetle; Larix laricina; Picea mariana; Pinus banksiana; bark; cone; diethyl maleate; glutathione S-transferase