Savori_1999_Pest.Sci_55_18

Quercetin and thymol blue were shown to synergize the toxicity of fenitrothion to Triatoma infestans with synergistic ratios of 1.89 and 2.65 respectively. These synergistic ratios were statistically significant at P<0.05. Both compounds inhibited glutathione S-transferases (GST) in vitro, with pI50 values of 6.1 and 5.1 respectively. Quercetin or thymol blue caused in-vivo GST inhibition without affecting non-specific esterase (NSE) or acetylcholinesterase (AChE) activity. Incubation of [14C]fenitrothion with T. infestans or rabbit liver GST produced desmethylfenitrothion as the major metabolite, which was specifically diminished in the presence of 0.3 mM quercetin. [14C]Fenitrothion toxicokinetics study showed a significant decrease (P<0.05) in radioactivity due to polar metabolites when insects were pre-treated with quercetin. These facts suggest that both assayed chemicals may be active in synergizing fenitrothion toxicity due to their ability to prevent the detoxification of organophosphorus insecticides by GSH conjugation..