Atividade larvicida do extrato celular e de lectina extraídos de Chlorella vulgaris frente larvas em L4 de Aedes aegypti

Abstract

Dengue, chikungunya and zika are viral diseases caused by the transmitting agent Aedes aegypti. According to data from the World Health Organization (WHO), the numbers of cases of these infections are increasing, the main method of prevention being the use of chemical insecticides to combat the vector, which has provoked resistance in the populations. The search for insecticides extracted from natural sources has been an alternative, thus, microalgae appear as a new possibility because they present biodegradable and non-toxic bioactives. Therefore, this research aimed to use the cell extract and Chlorella vulgaris lectin on A. aegypti to investigate larvicidal activity and inhibition on trypsin in the fourth larval stage (L4). The biomass of C. vulgaris was grown in Bold's Basal Medium. The biomass was concentrated and resuspended in a proportion of 10% w / v in 0.1 M Tris-HCl-NaCl buffer, pH 7.5 for the preparation of the cell extract by magnetic stirring for 9h and later performed hemagglutinating activity. Lectin was purified using anionic chromatography (DEAE-Sephadex) and Superdex 75 molecular exclusion. Cell extract at concentrations of 3.13% to 100%, and lectin from 25 to 200 μg mL-1, were applied to the larvae A. aegypti L4 during the 72-hour period following WHO recommendations. The cell extract showed an LC50 value with 3 hours (LC50 = 43.50%) and 24 hours (LC50 = 10.62%). While lectin showed LC50 at 24 hours (164.2 μg mL-¹), 48 hours (125.3 μg mL-¹) and 72 hours (106.5 μg mL-1). To observe the mechanism of action of intestinal trypsin, the LC50 of the cell extract containing 260 μg ml-1 of protein was applied to the fourth stage of A. aegypti larvae. Upon reaching the fourth stage, the larvae were incubated with the microalgae cell extract for a total period of 10 hours, and every 2 hours trypsin activity was performed. It was observed that the longer the cell extract treatment time with the larvae, the greater the reduction in intestinal extract trypsin activity. There was a 34.93% reduction in activity from the initial time with 2 hours to the final time with 10 hours. Thus, the present study using the cell extract, as well as the lectin isolated from C. vulgaris, appears as a new larvicidal potential of A. aegypti.