Extratos termorresistentes de sementes da caatinga: atividade larvicida e efeitos morfofisiológicos em Aedes aegypti e Aedes albopictus

Abstract

Arboviruses constitute a significant group of viral diseases primarily transmitted by hematophagous mosquitoes, notably Aedes aegypti (Linnaeus, 1762) and A. albopictus (Skuse, 1894). Conventional management strategies for these diseases predominantly rely on synthetic chemical insecticides as the primary control measure. However, this approach raises concerns regarding environmental toxicity and the potential development of resistance among mosquito populations. In light of these challenges, botanical insecticides, including plant extracts, represent a compelling alternative due to their biocompatibility and diverse modes of action, minimizing environmental impacts and insect resistance. This study investigates the insecticidal properties of extracts from the seeds of two legumes indigenous to the Caatinga biome, specifically Amburana cearensis ((Allem.) A. C. Smith) and Erythrina velutina (Willd.), against A. aegypti and A. albopictus larvae (L4). The extraction process involved solubilizing the seed powder in distilled water (1:10, w/v) at a temperature of 80 °C. The lethal concentrations for 50% (LC50) and 90% (LC90) of the larvae were assessed over 24 and 48 hours. Morphological alterations were examined using a stereomicroscope equipped with a camera, and larval development was monitored for 15 days. Furthermore, zymographic analyses were conducted to assess the inhibition of digestive proteases in the treated larvae. The results indicated that both extracts exhibited larvicidal activity, with A. cearensis extract demonstrating particularly notable efficacy. Specifically, the extract recorded LC50 values of 0,45 mg/mL and 0,23 mg/mL for 24 and 48 hours in A. aegypti, respectively, and LC50 values of 0,34 mg/mL and 0,11 mg/mL in A. albopictus. Additionally, A. cearensis extract reduced the enzymatic activity of intestinal proteases of both species by more than 70%, while E. velutina extract had no significant effect. Delays in larval development in A. albopictus suggest a pronounced influence of protease inhibition resulting from A. cearensis extract. Morphological changes suggest the presence of other deleterious effects of the extracts: acetylcholinesterase inhibition (A. cearensis and E. velutina), disruption of chitin synthesis, and internal tissue damage or infection leading to melanization (E. velutina). This study highlights the promising potential of A. cearensis and E. velutina extracts for larval control of A. aegypti and A. albopictus, with A. cearensis extract emerging as a particularly viable candidate for the development of botanical larvicides. The findings underscore the importance of plant biodiversity within the Caatinga biome in the creation of bioproducts, thereby enhancing its cultural, biotechnological, and economic significance while contributing to integrated management strategy for arboviral diseases.