Potencial de extratos fenólicos de cascas de Piptadenia gonoacantha no controle in vitro de Xanthomonas citri pv. eucalyptorum comb. nov.

Abstract

The genus Xanthomonas is a group of bacteria that can cause significant damage to plants, including eucalyptus, especially during the seedling production stage. Xanthomonas spp. infections in eucalyptus occur mainly in the nursery phase, where high humidity conditions favor the spread of the bacteria. Preventive management is based on irrigation control, use of nursery cover, adequate spacing between seedlings, sterilization of materials, and elimination of contaminated plants and waste, reducing the inoculum source and the spread of the disease. Treatment with chemical products may be an option, but it must be carried out with caution to minimize environmental impacts and ensure effectiveness in disease control. Therefore, this project aimed to analyze the potential of phenolic compounds in inhibiting the growth of Xanthomonas citri pv. eucalyptorum comb. nov. Piptadenia gonoacantha bark was subjected to air drying, grinding, and sieving. The extraction process employed 50% ethanol, 50% acetone, and water as solvents. Phenol quantification was performed using the Folin-Denis colorimetric and gravimetric methods. The extracts were lyophilized, and the phenolic compounds were dissolved in distilled water at concentrations of 10, 20, 30, 40, and 50 mg/mL. Bacterial sensitivity was evaluated by means of an antibiogram using the disk diffusion technique, with sodium rifampicin as a positive control. The 50% acetone extract showed the highest solids yield (25.40%), followed by 50% ethanol (22.70%), while water resulted in the lowest yield (17.04%), demonstrating the greater efficiency of organic solvents in extracting the compounds of interest. Similarly, the quantification of total phenols showed high concentrations of these compounds, confirming the effectiveness of the method used, especially in the extracts obtained with 50% ethanol (2.12%) and 50% acetone (2.06%), while water showed a lower total phenol content (1.04%). The phenolic extracts did not show antimicrobial activity against X. citri pv. eucalyptorum at the tested concentrations. In contrast, the positive control with antibiotic confirmed the methodological adequacy of the assay.