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DOI: 10.1055/s-2007-986907
Antimicrobial activity of D:A-friedo-nor-oleanane triterpenoids
The study of the antimicrobial activity (MIC and MBC) of two natural triterpenophenols: 6-deoxoblepharodol (1), 8-epi-6-deoxoblepharodol (2) and two derivatives: 2,3-diacetoxy-6-deoxoblepharodol (3) and 2,3-diacetoxy-8-epi-6-deoxoblepharodol (4) obtained after acetylation, were determined. The natural products showed antimicrobial activity against Gram positive bacteria. The relation structure-activity demonstrates that the presence of the hydroxyl groups in C2 and C3 is necessary for antimicrobial activity.
We studied the mode of action of 1 and 2 against Bacillus subtilis. The time-kill curves for both compounds verified that inclusion of either compound in the log phase was bactericidal (> or=3 log10 CFU/ml reduction). However, when 2 was added in the lag phase it reduced the initial inoculum by 2-log10 in the nine hours of treatment (bacteriostatic activity), while 1 showed bactericidal activity.
The activity of 1 was bactericidal at different bacterial concentrations (107, 106, 105, and 104 UFC/ml), where 2 showed bacteriostatic activity for all inoculum densities except for 107 UFC/ml, in which it was inactive.
R1 |
R2 |
R3 |
R4 |
|
1 |
OH |
OH |
–- |
–- |
2 |
–- |
–- |
OH |
OH |
3 |
AcO |
AcO |
–- |
–- |
4 |
–- |
–- |
AcO |
AcO |
Acknowledgements: This study was supported by Spanish Grants CTQ2006–13376-BQU