Avaliação do potencial antimicrobiano de nanoemulsões à base de compostos de óleos essenciais no controle de espécies de Xanthomonas causadoras do cancro cítrico

Abstract

Citrus canker is one of the most relevant diseases that affect citrus crops, being responsible for serious economic losses to citrus fruit producers and traders. This disease is caused by Gram-negative bacteria of the genus Xanthomonas, which can lead to premature fruit fall and total loss of plants present in the infected area. Nowadays, the control of citrus canker is carried out through methods in the field of prevention of the proliferation of the etiological agent of the disease combined with the use of copper-based compounds that inhibit the development of the bacterium. However, the search for more sustainable alternatives that are in fact effective in eradicating the disease is of general interest. In this work, the potentials of antimicrobial action of eugenol, thymol, geraniol and menthol (major compounds of essential oils) and essential oil (EO) of ginger against two strains of Xanthomonas that cause citrus canker (Xac and Xau-B) were investigated. In order to enhance its action spectrum, nanoemulsions were produced for each compound and oil, which underwent suspension analysis to characterize particle sizes and stability. The thymol and ginger EO nanoemulsions had the smallest particle sizes and the highest stability. However, of these two, only the thymol nanoemulsion showed the ability to inhibit the development of both strains of bacteria, with minimum inhibitory concentrations (MIC) of 0.03% (v/v), along with eugenol nanoemulsions (with MIC of 0.03% (v /v) for Xac and 0.02% (v/v) for Xau-B) and geraniol (with MIC of 0.06% (v/v) for both bacteria). Thymol was the compound with the highest minimum bactericidal concentrations (MBC), with values of 0.03% (v/v) for both bacterial strains. Eugenol showed MBC only against Xau-B, at a concentration of 0.03% (v/v). Geraniol did not show bactericidal activity, which suggests a bacteriostatic action of this compound with the tested microorganisms. In general, Xac was more susceptible to bacteriostatic activities, while Xau-B was more sensitive to bactericidal actions. The ginger EO and menthol nanoemulsions did not show any antimicrobial activity.