Antimicrobial activity of triterpene acids against phytopathogens / atividade antimicrobiana de triterpenos ácidos contra fitopatógenos

Phytopathogenic microorganisms, responsible for causing diseases in various types of plantations, have an immense impact on crops, reducing food production, which is one of the main problems of agriculture. Antibiotics in association with cupric fungicides have been commonly used to solve this problem, but result in toxic residues to humans, animals and the environment, in addition to not being as effective as expected. Natural products, such as triterpenes, have become an important source of new substances to fight pathogens. In this study, the triterpenes ursolic acid, oleanolic acid and gypsogenic acid were re-isolated from Miconia stenostachya . The identification of all substances was carried out based on data obtained from 1 H NMR, 13 C-NMR and/or comparison with authentic standards. In the assays of antimicrobial activity against nine phytopathogenic bacteria, the triterpene gypsogenic acid was the most effective with a MIC value of 3.12; 25 and 100 µg/mL, for bacteria Ralstonia solanacearum , Pseudomonas syringae and Streptmyces scabiei , respectively. The cytotoxic activity results of gypsogenic acid in GM7492A cells (human fibroblasts) indicated that the substance promoted toxic effects in the strain only at higher concentrations (above of 500 µg/mL – 1,027.3 µM).