Trypsin inhibitor from Enterolobium contortisiliquum seeds impairs Aedes aegypti development and enhances the activity of Bacillus thuringiensis toxins.

Background: Disease vector insects are barriers for human development. The use of synthetic chemicals to control these vectors has caused damage to the environment and contributed to the arising of resistant insect populations. This has led to an increased search for plant-derived molecules with insecticidal activity or that show synergistic effects with known insecticidal substances, such as protease inhibitors. Thus, we aimed to evaluate the effect of Enterolobium contortisiliquum trypsin inhibitor (EcTI) on Aedes aegypti development as well as its effect on insecticidal activity of Bacillus thuringiensis toxins.

Results: EcTI showed an apparent molecular mass about of 20 kDa in SDS-PAGE and was able to inhibit in vitro the activity of trypsin and proteases from midgut of Ae. aegypti larvae. EcTI was not able to cause acute toxicity on mosquito larvae even at 1000 μg mL , however it promoted a delay in larval development after prolonged exposure. The zymogram results for EcTI-treated larvae (from 50 to 200 μg mL ) showed an increase of midgut proteases activity as a larvae defense mechanism, however no changes in the enzyme profile was observed. These same concentrations were able to enhance up to three fold the insecticidal activity of B. thuringiensis toxins without causing toxicity to Artemia sp. nauplii, a non-target organism.

Conclusions: The results offer a novel approach by combining EcTI and B. thuringiensis toxins for combating Ae. aegypti larvae. © 2020 Society of Chemical Industry.