Evaluation of the antibacterial activity of the methylene chloride extract of Miconia ligustroides, isolated triterpene acids, and ursolic acid derivatives.

The methylene chloride extract of Miconia ligustroides (DC.) Naudin (Melastomataceae), the isolated compounds ursolic and oleanolic acids and a mixture of these acids, and ursolic acid derivatives were evaluated against the following microorganisms: Bacillus cereus (ATCC 14579), Vibrio cholerae (ATCC 9458), Salmonella choleraesuis (ATCC 10708), Klebsiella pneumoniae (ATCC 10031), and Streptococcus pneumoniae (ATCC 6305). The microdilution method was used for determination of the minimum inhibitory concentration (MIC) during evaluation of the antibacterial activity. The methylene chloride extract showed no activity against the selected microorganisms. Ursolic acid was active against B. cereus, showing a MIC value of 20 microg/mL. Oleanolic acid was effective against B. cereus and S. pneumoniae with a MIC of 80 microg/mL in both cases. The mixture of triterpenes, ursolic and oleanolic acids, did not enhance the antimicrobial activity. However, the acetyl and methyl ester derivatives, prepared from ursolic acid, increased the inhibitory activity for S. pneumoniae.