Isolation and characterization of antibacterial compounds from Euphorbia tirucalli against Xanthomonas axonopodis pv. citri

Xanthomonas axonopodis pv. citri (X. axonopodis pv. citri) is the cause of canker disease on lime trees that negatively affect plant health and fruit quality. This study focused on the comparison of the extraction yield and antibacterial properties of Euphorbia tirucalli against X. axonopodis pv. citri, phytochemical screening, quantifcation of phenolic and flavonoid contents of the fraction extract. The results showed that the ethyl acetate fraction (EA) (7.5 mg/mL) of E. tirucalli from Dak Nong province had the best activity against bacteria with diameter of inhibition zone determined 15.50 ± 0.50 mm, and the minimum inhibition concentration was 0.312 mg/mL. Alkaloids, flavonoids, tannins, and terpenoids were found in the EA fraction extract of E. tirucalli, whereas saponin did not appear in the extract. The phenolic and flavonoid content was in the range of 14.46 - 98.63 mg GEA/g and 90.34 - 408.86 µg QE/g, respectively. Column chromatography followed Nuclear Magnetic Resonance spectra were performed and the three compounds were identifed as scopoletin, gallic acid, and 3,3’,4’-tri - O - methylellagic acid. This study suggests that the extract from E. tirucalli and the isolated compounds can be used for managing of citrus canker disease.