The synergistic effects of insecticidal essential oils and piperonyl butoxide on biotransformational enzyme activities in Aedes aegypti (Diptera: Culicidae).
The biochemical mechanisms underlying the increased toxicity of several plant essential oils (thymol, eugenol, pulegone, terpineol, and citronellal) against fourth instar of Aedes aegypti L. when exposed simultaneously with piperonyl butoxide (PBO) were examined. Whole body biotransformational enzyme activities including cytochrome P450-mediated oxidation (ethoxyresorufin O-dethylase [EROD]), glutathione S-transferase (GST), and beta-esterase activity were measured in control, essential oil-exposed only (single chemical), and essential oil + PBO (10 mg/liter) exposed larvae. At high concentrations, thymol, eugenol, pulegone, and citronellal alone reduced EROD activity by 5-25% 16 h postexposure. Terpineol at 10 mg/liter increased EROD activity by 5 +/- 1.8% over controls. The essential oils alone reduced GST activity by 3-20% but PBO exposure alone did not significantly affect the activity of any of the measured enzymes. All essential oils in combination with PBO reduced EROD activity by 58-76% and reduced GST activity by 3-85% at 16 h postexposure. This study indicates a synergistic interaction between essential oils and PBO in inhibiting the cytochrome P450 and GST detoxification enzymes in Ae. aegypti.
Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6. rwaliwit@sfu.ca
Ranil
R
Waliwitiya
Russell A
RA
Nicholson
Christopher J
CJ
Kennedy
Carl A
CA
Lowenberger
D000330:Aedes / Q000201:enzymology*; D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004950:Esterases / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007306:Insecticides; D007814:Larva / Q000201:enzymology; D009822:Oils, Volatile; D010574:Pesticide Synergists; D010882:Piperonyl Butoxide
D007306:Insecticides; D009822:Oils, Volatile; D010574:Pesticide Synergists; D019363:Cytochrome P-450 CYP1A1; D005982:Glutathione Transferase; D004950:Esterases; D010882:Piperonyl Butoxide