Preliminary studies on the antibacterial activity of crude extracts and alkaloids from species of Aspidosperma

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Screening tests of hydroethanolic crude extracts of six species of Aspidosperma (Apocynaceae) against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa were performed. Aspidosperma ramiflorum Muell. Arg. showed good activity against Bacillus subtilis with MIC and MBC of 15.7 and 125 mu g/mL, moderate activity against Staphylococcus aureus with MIC and MBC of 250 and 500 mu g/mL, and weak activity against Escherichia coli with MIC and MBC of 1000 mu g/mL. Aspidosperma pyricolum Muell. Arg. (MIC/MBC 125/250 mu g/mL) and Aspidosperma olivaceum Muell. Arg. (MIC/MBC 250/> 1000 mu g/mL) displayed moderate antibacterial activity against Bacillus subtilis. Separation of the crude extract of Aspidosperma ramiflorum was performed according to the usual acid-base process, which produces alkaloid mixtures and closely related metabolites. The basic fraction was active against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, with MICs of 31.2, 62.5, and 250 mu g/mL, respectively. The basic fractions were more active than the acid fractions, probably because they contained some active alkaloids and/or closely related metabolites absent from the other fractions, or they contained a higher concentration of these active compounds.471110851089Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundacao AraucariaPrograma de Pos-graduacao em Ciencias Farmaceuticas da Universidade Estadual de MaringaConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

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 37ºC 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 µg/mL) and S. aureus (MIC = 500 µg/mL), and was inactive against the Gram-negative bacteria E. coli and P. aeruginosa (MIC > 1000 µg/mL). Fractions I and II were inactive against standard strains at concentrations of <=1000 µg/mL and fraction III displayed moderate antibacterial activity against B. subtilis (MIC = 500 µg/mL) and S. aureus (MIC = 250 µg/mL). Fraction IV showed high activity against B. subtilis and S. aureus (MIC = 15.6 µg/mL) and moderate activity against E. coli and P. aeruginosa (MIC = 250 µg/mL). Fraction V presented high activity against B. subtilis (MIC = 15.6 µg/mL) and S. aureus (MIC = 31.3 µg/mL) and was inactive against Gram-negative bacteria (MIC > 1000 µg/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 µg/mL) and E. faecalis (MIC = 50 µg/mL), with EC50 of 8 and 2.5 µg/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