Antibacterial activity of indole alkaloids from Aspidosperma ramiflorum.
We evaluated the antibacterial activities of the crude methanol extract, fractions (I-V) obtained after acid-base extraction and pure compounds from the stem bark of Aspidosperma ramiflorum. The minimum inhibitory concentration (MIC) was determined by the microdilution technique in Mueller-Hinton broth. Inoculates were prepared in this medium from 24-h broth cultures of bacteria (10(7) CFU/mL). Microtiter plates were incubated at 37 masculineC and the MICs were recorded after 24 h of incubation. Two susceptibility endpoints were recorded for each isolate. The crude methanol extract presented moderate activity against the Gram-positive bacteria B. subtilis (MIC = 250 microg/mL) and S. aureus (MIC = 500 microg/mL), and was inactive against the Gram-negative bacteria E. coli and P. aeruginosa (MIC > 1000 microg/mL). Fractions I and II were inactive against standard strains at concentrations of < or =1000 microg/mL and fraction III displayed moderate antibacterial activity against B. subtilis (MIC = 500 microg/mL) and S. aureus (MIC = 250 microg/mL). Fraction IV showed high activity against B. subtilis and S. aureus (MIC = 15.6 microg/mL) and moderate activity against E. coli and P. aeruginosa (MIC = 250 microg/mL). Fraction V presented high activity against B. subtilis (MIC = 15.6 microg/mL) and S. aureus (MIC = 31.3 microg/mL) and was inactive against Gram-negative bacteria (MIC > 1000 microg/mL). Fractions III, IV and V were then submitted to bioassay-guided fractionation by silica gel column chromatography, yielding individual purified ramiflorines A and B. Both ramiflorines showed significant activity against S. aureus (MIC = 25 microg/mL) and E. faecalis (MIC = 50 microg/mL), with EC50 of 8 and 2.5 microg/mL for ramiflorines A and B, respectively, against S. aureus. These results are promising, showing that these compounds are biologically active against Gram-positive bacteria.
Tanaka
J C A
JC
Departamento de Química, Universidade Estadual de Maringá, Maringá, PR, Brazil.
Silva
C C da
CC
Oliveira
A J B de
AJ
Nakamura
C V
CV
Dias Filho
B P
BP
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D030009:Aspidosperma / Q000737:chemistry*; D001412:Bacillus subtilis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects; D026121:Indole Alkaloids / Q000737:chemistry / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects
D000900:Anti-Bacterial Agents; D026121:Indole Alkaloids; D010936:Plant Extracts