Canadian Forest Service Publications

Inhibition of insect gluthathione s-tranferases (GSTs) by conifer extracts. 2014. Wang, Z.; Zhao, Z.; Abou- Zaid, M.; Arnason, T.; Liu, R.; Washe-Roussel, B.; Waye, A.; Liu, S.; Saleem, A; Wei, Q,; Scott, I. Archives of Insect Biochemistry and Physiology 87:234-249.

Year: 2014

Issued by: Great Lakes Forestry Centre

Catalog ID: 35816

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1002/arch.21192

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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.

Plain Language Summary

The objective of the research was to evaluate the in vitro GST inhibition of conifer cone and bark extracts using CPB midgut and fat body homogenates as an enzyme source in order to measure relative activity and identify the compounds responsible for the GST inhibition.