Pupation inhibition and larvicidal activity of tyrosinase on Culex pipiens third-instar larvae

Background Mosquitoes are considered to be the main vector of a variety of diseases in both humans and domesticated animals. The development of insecticide resistance and the limitations of traditional insecticide-based strategies have resulted in significant efforts to develop eco-friendly, alternative methods. Main body In this study, nine fungi species were screened to produce tyrosinase enzyme. This was done in order to evaluate its inhibitory activity against Culex pipiens third-instar larvae. The extracellular tyrosinase was produced by five strains. Aspergillus tamarii NRC3 was found to possess the highest tyrosinase activity and was therefore used in this study. Some factors were studied to enhance the production of the enzyme. The enzyme was partially purified using ammonium sulfate at a 70% saturation, giving 1.861 purification fold. The toxicity on Culex pipiens varied, depending upon the tyrosinase concentration and the period of exposure. In addition, notable histological effects were seen in the midgut region. Conclusions A concentration of 80% on third-stage larvae showed 90% inhibition in the formation of pupae at 72 h post-treatment. In addition, a significant cellular microvillus disruption was seen in the midgut region at 24 h post-treatment.