Antibacterial Activity of tinctures from tree leaves belonging to the Bignoniaceae family and their synergistic effect with antibiotics.

TORRES C. A; NUÑEZ MARÍA BEATRIZ; ISLA MARÍA INÉS; CASTRO MARCELA PAOLA; GONZALEZ ANA MARÍA; ZAMPINI IRISCATIANA

Pharmacognosy Journal

Pharmacognosy Network Worldwide

Año: 2015 vol. 7 p. 400 - 405

0975-3575

Context: Some species of Bignoniaceae are widely used in medicinal practiceby the natives of South America. Aims: Tinctures and infusions fromtwelve tree species of this family were evaluated for in vitro antibacterialactivity against pathogenic bacteria. The effect of interactions betweenthe four most active extracts and conventional antibiotics was also evaluated.Methods and Material: Bioautography and disc diffusion methodswere used to select the most active extracts, then agar macrodilution andbroth microdilution method were used to determine the minimal inhibitoryand minimal bactericidal concentration (MIC and MBC). Time-kill assayand checkerboard method were employed to determine the type ofantimicrobial effect and synergism, respectively. Results: It could be determinedthat tinctures from Catalpa bignonioides, Handroanthus pulcherrimus,Tabebuia nodosa and Tecoma stans were able to inhibit bacterialgrowth. The MIC and MBC observed were between 125-1000 μg GAE/ml and 500-1000 μg GAE/ml, respectively. The tested extracts were moreeffective against Gram-positive microorganisms. Time-kill experimentsindicated bacteriostatic activity. Phytochemical screening showed terpenoids,phenols and flavonoids. Alkaloids were detected only in Tecomastans. Among these combinations, the best was Tabebuia nodosa extractplus gentamicin. In most cases, MIC values were reduced 16-32 times forantibiotics, and even 8-16 times for extracts. Conclusion: These resultsrevealed that some of the selected combinations could efficiently inhibitthe growth of tested strains at lower concentrations than those requiredfor the lonely use of the antimicrobial. These extracts would improve theefficacy of antibiotics against resistant bacteria, hence they could be usedfor anti-infective therapy.Context: Some species of Bignoniaceae are widely used in medicinal practiceby the natives of South America. Aims: Tinctures and infusions fromtwelve tree species of this family were evaluated for in vitro antibacterialactivity against pathogenic bacteria. The effect of interactions betweenthe four most active extracts and conventional antibiotics was also evaluated.Methods and Material: Bioautography and disc diffusion methodswere used to select the most active extracts, then agar macrodilution andbroth microdilution method were used to determine the minimal inhibitoryand minimal bactericidal concentration (MIC and MBC). Time-kill assayand checkerboard method were employed to determine the type ofantimicrobial effect and synergism, respectively. Results: It could be determinedthat tinctures from Catalpa bignonioides, Handroanthus pulcherrimus,Tabebuia nodosa and Tecoma stans were able to inhibit bacterialgrowth. The MIC and MBC observed were between 125-1000 μg GAE/ml and 500-1000 μg GAE/ml, respectively. The tested extracts were moreeffective against Gram-positive microorganisms. Time-kill experimentsindicated bacteriostatic activity. Phytochemical screening showed terpenoids,phenols and flavonoids. Alkaloids were detected only in Tecomastans. Among these combinations, the best was Tabebuia nodosa extractplus gentamicin. In most cases, MIC values were reduced 16-32 times forantibiotics, and even 8-16 times for extracts. Conclusion: These resultsrevealed that some of the selected combinations could efficiently inhibitthe growth of tested strains at lower concentrations than those requiredfor the lonely use of the antimicrobial. These extracts would improve theefficacy of antibiotics against resistant bacteria, hence they could be usedfor anti-infective therapy.