Avaliação da atividade antimicrobiana in vitro do extrato de tabernaemontana

Abstract

Several Tabernaemontana species have been studied due to their several alkaloids with pharmacological activity. The aim of this work was to evaluate the in vitro antimicrobial action of the extract from stem barks of Tabernaemontana catharinensis A. DC. against strains of Staphylococcus aureus and Pseudomonas aeruginosa, microorganisms that cause several infections. Bacterial susceptibility tests were performed by the Kirby-Bauer method, consisting in antibiotic disk diffusion in Mueller Hinton medium. Inhibition tests were performed with solutions of T. catharinensis dry crude extract dissolved in ethanol 70% (v/v) at 1.0 mg mL -1, which became 0.005 mg mm- 2 when applied to 20 mm2 disks. As negative control, assays were carried out in plates containing P. aeruginosa and disks with ethanol 70% (v/v). Positive control consisted of disks containing the antibiotics ceftriaxone sodium (0.25 mg mm- 2 disk area), tetracycline (0.005 mg mm- 2) and cephalexin (0.005 mg mm- 2). Extract solution at 0.005 mg mm- 2 inhibited Staphylococcus aureus, with 0.6cm halo mean diameter. The inhibition halo for Pseudomonas aeruginosa was on average 1.2 cm. Tetracycline, cephalexin and negative control (ethanol 70% v/ v) did not show antimicrobial action, whereas ceftriaxone sodium resulted in 2.2 and 1.0cm mean inhibition halo diameters for P. aeruginosa and Staphylococcus aureus, respectively.