Avaliação da atividade antimicrobiana do óleo essencial de distintos quimiotipos de Lippia alba (Mill.) N.E.Brown

Abstract

Lippia alba is a native species, known as "erva cidreira", currently used in folk medicine for the treatment of several diseases. Pharmacologic studies attributed their antimicrobial activity to the terpenoids present in the essential oils. Considering the variation on essential oil composition among L. alba accessions, the present work aimed to determine the essential oil composition of seven accession of L. alba collected in South Brazil, and to evaluate their antimicrobial activity against a panel of 22 bacterial and 9 yeast species. Essential oils were extracted by hydrodistillation and analyzed by GC and GC/MS. Antimicrobial activity (ID50 and MIC) were determined by a serial dilution method (0 to 10 mg/ml) on microplates with growth evaluation by absorbance at 595nm. For ID50 and MIC determination were considered the essential oil concentrations that reduced microbial growth on 50% and 90%, respectively. Bactericidal and bacteriostatic activities were determined after 3h treatment of the microorganisms with their individual MIC of each essential oil. Based on their main constituents, the results allowed characterizing the seven accessions of L. alba as chemotypes: citral, 1,8-cineol/camphor, linalool, linalool/mircene/camphor, carvone/caryophyllene, linalool/1,8-cineol/germacrene D, and limonene. Among these chemotypes, citral essential oils showed the largest antimicrobial spectrum, inhibiting both bacteria and yeasts. Oils with high concentration of carvone/caryophyllene, and limonene, were particularly effective against yeasts, and oils from chemotypes linalool and linalool/1,8-cineol/germacrene D exhibited inhibitory activity against several Gram positive and negative bacteria. At the MIC, citral showed bactericide effect on yeasts and Salmolella. However, other oils showed just bacteriostatic effects on most microorganisms. In general, our results confirm the activity of L. alba essential oils on both clinical and industrial microorganisms, but point out the necessity to properly evaluate essential oil composition to choose those more effective for the control of a specific microorganism.