Investigação da atividade fitotóxica e citogenotóxica de ésteres semissintéticos obtidos a partir de fenóis e do ácido fenoxiacético em Lactuca sativa e Sorghum bicolor

Abstract

In order to maintain agricultural production, the use of pesticides has become indispensable, however, its harmfulness to the environment and human health has been questioned. Among the most used pesticides, herbicides stand out, targeting the control of invasive plants, and their continuous and disorderly use can trigger several problems such as resistance and the impact caused to the environment and human health. Thus, it becomes necessary to search for new herbicides and alternative control methods. Compounds of natural origin and their derivatives are attractive options for obtaining new compounds with herbicidal properties, thus, semi-synthetic esters were synthesized from natural phenols and phenoxyacetic acid. Therefore, the objective was to evaluate the effect of phenyl 2-phenoxyacetate esters and natural phenols in plant bioassays. Seven semi-synthetic molecules – carvacrol ester, thymol ester, eugenol ester, guaiacol ester and vanillin ester, p-cresol ester and β-naphthol ester – at concentrations 0;0.1875; 0.375; 0.750; 1.50 and 3 mmol. L-1 were applied to model plants Lactuca sativa and Sorghum bicolor. The herbicidal potential of esters was evaluated for germination and initial development of seedlings and for the induction of alterations in the mitotic cycle of meristematic cells of L. sativa roots. The ester molecules of thymol, eugenol, carvacrol, guaiacol and vanillin showed greater interaction with the plants than the other molecules, causing the most toxic effects on the initial development of L. sativa and S. bicolor. Root growth of L. sativa was inhibited by eugenol ester and guaiacol ester molecules at a concentration of 3 mmol/L, being similar to the 2,4-D positive control. In S. bicolor, the reduction of root growth was observed in treatments containing thymol ester (3 mmol/L), eugenol ester (3 mmol/L) and carvacrol ester (3 mmol/L). The aerial length of S. bicolor was inhibited by vanillin esters, eugenol, carvacrol and guaiacol ester. The increase of the mitotic index, of the total and individual frequency of chromosomal alterations in roots of L. sativa revealed the cytotoxic, genotoxic effects and the aneugenic mode of action of the tested molecules. These results can be associated with the interaction of the natural phenols present in the esters with the cell membrane and the induction of oxidative damage on the mitotic spindle, thus causing damage to the initial development of L. sativa and S. bicolor seedlings. Given these results, esters of the phenyl 2-phenoxyacetate class have great phytotoxic and cytogenotoxic potential, and may be useful in obtaining new bioherbicides.