Table 3.
MICs (in μg/mL) of crude leaf extract (APL), active fractions (APLa and APLd), 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (8) and chloramphenicol in the presence of PAßN and fold increase of activity (in parenthesis) against a panel of selected Gram-negative bacteria.
| Bacterial strains | Tested samples, MIC in μg/mL in presence of PAßN and fold increase of activity (in parenthesis) | ||||
|---|---|---|---|---|---|
| Leaf extract | Fractions from APL | Isolated compound | Reference antibiotic | ||
| APL | APLb | APLd | 8 | Chloramphenicol | |
| Escherichia coli | |||||
| ATCC8739 | 256 (4) | 4 (4) | 2 (8) | ≤2 (≥ 16) | ≤ 2 (≥ 1) |
| AG102 | 64 (8) | 32 (2) | 8 (16) | ≤ 2 (≥ 16) | 4 (8) |
| Enterobacter aerogenes | |||||
| ATCC13048 | 64 (4) | 4 (2) | ≤4 (≥ 64) | ≤ 2 (≥ 16) | 2 (8) |
| EA27 | 16 (64) | 64 (2) | 4 (128) | 64 (4) | 4 (8) |
| Klebsiella pneumoniae | |||||
| ATCC11229 | 128 (8) | ≤ 4 (≥ 4) | ≤ 4 (≥ 16) | ≤ 2 (≥ 16) | 4 (8) |
| KP55 | 128 (8) | 32 (2) | 4 (4) | ≤ 2 (≥ 16) | 16 (4) |
| Pseudomonas aeruginosa | |||||
| PA01 | 128 (0.5) | 32 (2) | 32(4) | ≤2 (≥ 128) | 8 (8) |
| PA124 | 128 (2) | 32 (2) | 128 (2) | 16 (2) | 64 (4) |
| Providencia stuartii | |||||
| ATCC29916 | ≤ 4 (≥ 2) | 32 (16) | 32(4) | 16 (4) | 16 (4) |
(-): MIC > 1024 μg/mL for crude extract APL, >512 for fractions APLb and APLd, 256 μg/mL for 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (8); (): values in parenthesis are fold increase of activity in the presence of PAßN at 30 μg/mL; MIC values in bold: significant antibacterial effects for MIC [18] and significant increase of activity in the presence of PAßN [19, 20]; fold increase of activity determined MIC of sample tested alone (Tables 1 and 2) versus MIC of the sample in the presence of PAßN. The MIC of PAßN was >256 mg/L for E. coli, E. aerogenes, K. pneumoniae, P. aerogenes, and P. stuartii strains.