Antimicrobial activity of tinctures from Tecoma stans leaves against some bacteria causing skin infections

TORRES, CAROLA ANALÍA; ZAMPINI, IRIS CATIANA; NUÑEZ, MARÍA BEATRIZ; CASTRO, MARCELA PAOLA; GONZALEZ, ANA MARÍA

Rosario

Encuentro; II Reunión Internacional de Ciencias Farmacéuticas; 2012

Facultad de Ciencias Bioquímicas y Farmacéuticas-Universidad Nacional de Rosario

Certain bacteria commonly live on the skin of many people without causing harm. However, these bacteria can cause skin infections if they enter the body through cuts, open wounds, or other breaks in the skin. Staphylococcus aureus is a bacterium that is carried on the skin or in the nose of approximately 25% to 30% of healthy people without causing infection. Most of these skin infections are minor, are not spread to others, and usually can be treated without antibiotics. However, nowadays there are more resistant strains because of the abusive and indiscriminate use of antimicrobial compounds. Several alternatives have been suggested to solve this problem. The systematic screening of antibacterial plant extracts represents a continuous effort to find new compounds with the potential to act as antimicrobial agents. The barks and leaves of some species of Tecoma genus (Bignoniaceae) are known for the anti-inflammatory, antirheumatic, antimicrobial or antisyphilitic activity of their extracts. The aim of this work was to evaluate the effect of hydroalcoholic extract (tincture) of leaves of Tecoma stans against Staphylococcus genus bacteria. The microorganisms used in this work were Staphylococcus aureus ATCC 29213, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228 and six clinical isolates of Staphylococcus aureus. The qualitative determination of the antibacterial activity was assessed by the agar disk diffusion method and the bioauthography assay. Minimal inhibitory concentration (MIC) was also determined by macrodilution and microdilution methods. For these assays the tincture was dried and resuspended in dimethyl sulfoxide. Dilutions of crude extract (range concentration between 62.5 and 1000 µg of phenolic compounds/ml expressed as galic acid equivalent (GAE)/ml of tincture) were prepared. All bacteria were sensitive. The most sensitive was S. epidermidis with MIC value of 125 µg GAE/ml, followed by S. aureus ATCC 29213 with MIC value of 250 µg GAE/ml and the others strains with MIC value of 500 µg GAE/ml. By means of bioautography it was determined that the tincture was active. This assay detected bands that inhibited the bacterial development. These inhibitory bands appear phenolic metabolites. The results of this study suggest that the tincture of leaves of Tecoma stans possesses antimicrobial properties. This result would support its use for the treatment of skin infectious, mainly caused by Staphylococcus strains. In terms of species conservation, these results show that leaf material is useful for antimicrobial uses, and it could be taken without any detrimental effect on the plant.