Abstract
Herbicides are agrochemicals applied in the control of weeds. With the frequent and repetitive use of these substances, serious problems have been reported. Compounds of natural origin and their derivatives are attractive options to obtain new compounds with herbicidal properties. By aiming to develop compounds with potentiated herbicidal activity, phenoxyacetic acids were synthesized from eugenol and guaiacol. The synthesized compounds were characterized and the herbicidal potential of phenoxyacetic acids and precursors was evaluated through bioassays regarding the germination and initial development of Lactuca sativa and Sorghum bicolor seedlings, with the induction of DNA damage. The induction of changes in the mitotic cycle of meristematic cells of roots of L. sativa was also analyzed. At the concentration of 3 mmol L-1, phenols and their respective phenoxyacetic acids presented phytotoxic and cytotoxic activities in L. sativa and S. bicolor. Eugenol and guaiacol also presented genotoxic action in L. sativa. The toxic effect of eugenoxyacetic acid was more pronounced in L. sativa than in S. bicolor, similar to the commercial 2,4-D herbicide. Molecular properties of the phenols and their derivatives phenoxyacetic acids were compared with the ones obtained for the herbicide 2,4-D, where it was found a correlation between their molecular properties and bioactivity.
Highlights
The 2,4-dichlorophenoxyacetic (2,4-D) and 4-chloro-2-methylphenoxyacetic acids (MCPA) were the first auxinic herbicides used in agriculture
The obtention of eugenoxyacetic and guaiacoxyacetic acids from the eugenol and guaiacol phenols was performed since the group -CH2COOH was presented in the structures of 2,4-D and MCPA auxin herbicides
The results demonstrated that the only treatment that caused damage that is not amenable to repair was glyphosate, which is used as a positive control
Summary
The 2,4-dichlorophenoxyacetic (2,4-D) and 4-chloro-2-methylphenoxyacetic acids (MCPA) were the first auxinic herbicides used in agriculture. In 1942, Zimmerman and Hitchcock showed that certain chlorinated phenoxyacetic acids, such as 2,4-D, were more active than the naturally occurring hormone indolylacetic acid (IAA) and they were not rapidly degraded in the plant. Due to the selectivity presented by this class of herbicides, the use of these substances innovated and revolutionized agriculture worldwide due to the control of broadleaf weeds. Several species of dicot weeds which are difficult to control using other herbicides are susceptible to 2,4-D. In bacteria found in the soil, for example, genes that are related to 2,4-D tolerance were discovered and their
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