Toxicidade aguda do herbicida Boral® 500 SC (Sulfentrazone) em Drosophila melanogaster

Abstract

The herbicide Sulfentrazone (SULF) is used in agriculture for pre-emergence control of mono- and dicotyledonous weeds. Its mechanism of action is by inhibiting the enzyme Protoporphyrinogen oxidase (PPOX), which participates in the biosynthesis pathway of chlorophyll and heme. Due to its high half-life in the soil, the low concentration needed to generate an effect, and high evolutionary conservation of the biosynthesis pathway, SULF has a high potential to damage non-target organisms present in application sites. Among non-target organisms, it is possible to include insects that do not necessarily harm human activities, which are being globally affected by various factors, such as the use of herbicides. In this perspective, Drosophila melanogaster, better known as the fruit fly, is used as a model organism for toxicological studies of substances in insects. Thus, this dissertation aimed to evaluate the effect of Boral® 500 SC (SULF) on D. melanogaster exposed to acute concentrations. For this purpose, the fruit flies were exposed to concentrations ranging from 10-300 mg.L-1 of the herbicide for seven days. Thus, it was possible to verify the increase in mortality in a dose and time-dependent manner in exposed flies. Based on this result, concentrations of 30, 150, and 300 mg.L-1 were chosen for the negative geotaxis assay, which demonstrated a significant decrease in the climbing locomotor capacity of animals exposed for four days. The locomotor capacity was significantly reduced among the groups exposed to concentrations of 30 and 150 mg.L-1, but not between 150 and 300 mg.L-1. Thus, for subsequent assays, flies exposed to concentrations of 30 and 150 mg.L-1 were evaluated. In addition to the decrease in climbing locomotor capacity (negative geotaxis), there was a reduction in exploratory locomotor capacity (open field assay). Collectively, our results suggest that flies exposed to Boral® 500 SC (SULF) have a higher energy demand to deal with the effects caused by the herbicide. (1) This was seen by decreasing weight and increasing total protein. (2) Activation of the heme biosynthesis pathway, by the accumulation of protoporphyrin IX (intermediate of heme synthesis), increase in total heme in the head, and induction of the PBGS enzyme (δ-ALA-D in mammals). In conjunction with (3) increased oxidative damage in the body as seen by the TBARS assay and (4) increased activity of SOD and GST enzymes. Along with (5) increased MTT abatement capacity. Thus, in this study, it was demonstrated that the increase in energy demand, to supply the cellular processes altered by exposure to the herbicide, maybe the main sign of the Boral® 500 SC (SULF) toxicity in Drosophila melanogaster.