Atividade antimicrobiana e antibiofilme de óleos essenciais de Croton grewioides sobre fitopatógenos do gênero Xanthomonas

Abstract

Bacterial diseases caused by species of the genus Xanthomonas, such as X. campestris pv. campestris (XCC) and X. campestris pv. melonis (Xmel), significantly compromise agricultural productivity in several economically important crops. Given the limitations of traditional control methods, such as the extensive use of synthetic agrochemicals, essential oils (EOs) from medicinal plants are highlighted as sustainable alternatives. This thesis aimed to evaluate the potential use of C. grewioides EOs (CGEOs), as well as their antimicrobial and antibiofilm activity against the phytopathogens XCC and Xmel. The first article of the thesis consisted of a systematic and bibliometric review of the literature on CGEOs, revealing 24 biological activities attributed to these oils. Five possible chemotypes were identified (estragole, methyl eugenol, eugenol, anethole and (E)-anethole), with estragole and (E)-anethole proposed as chemical markers of the species. In subsequent experimental studies, the compounds eugenol (81.67–84.92%), methyl eugenol (70.10%), and methyl chavicol (69.17%) were identified as major. Evaluating the effect of CGEOs on Xmel, it was observed that the accessions CGR – 106, CGR – 107, CGR – 220 and the combination of eugenol + methyl chavicol compounds presented the lowest MIC (1000 μg.mL−1 ). The MBC for all CGEOs and their compounds was higher than 4000 μg.mL−1 . The kinetics of death showed a reduction in cell prediction from 120 min. It was also possible to observe that CGEOs were able to permeabilize the cell membrane and reduce biofilm formation. For XCC, we observed that biofilm formation was significantly reduced, with eugenol being the compound with the highest antibiofilm activity (VIP = 2.54, PLS-DA). The eradication of preformed biofilms reached up to 71.47% (CGR – 220). Bacterial motility was also inhibited, with CGR – 311 presenting a smaller displacement area (0.35 cm²). Cellulase, endoglucanase, and protease activities were significantly reduced, with inhibitions of 75.9% for endoglucanase (CGR – 204), 59.0% for cellulase (CGR – 204), and 64.0% for protease (CGR – 107). These results highlight the potential of CGEOs as antivirulence agents for the sustainable control of phytopathogens, contributing to the reduction of dependence on synthetic agrochemicals in agriculture.