Composição química e avaliação do potencial antimicrobiano dos óleos essencias de Ruellia asperulla (Mart. ex ness) Lindau e Ruellia paniculata L. (Acanthaceae)

Abstract

The genus Ruellia L. comprises about 300 species, which are broadly distributed in tropical and subtropical regions of the planet. Among the species that comprise the genus, are Ruellia asperula and Ruellia paniculata, known popularly as "Melosa" and "Melosa-purple". Phytochemical research and antimicrobial activity against species belonging to the genus Ruellia are scarce, however the literature reveals that some of these species are widely used in folk medicine. Thus, this study sought to describe the chemical composition and evaluate the antibacterial effect of essential oils from aerial parts of Ruellia asperula and Ruellia paniculata, on the growth of Streptococcus mutans ATCC 25175, Streptococcus oralis ATCC 10557, Streptococcus parasanguinis ATCC 903, Streptococcus salivarius ATCC 7073, Streptococcus sobrinus ATCC 6715, Pseudomonas aeruginosa ATCC 9027 e Klebsiella oxytoca ATCC 13182, both in planktonic form as in biofilms. The essential oils were obtained and their constituents analyzed by gas chromatography and mass spectrometry (GC / MS). Different methodologies were used to check the antimicrobial potential. Among these are the minimum inhibitory concentration (MIC) determination of the death curve and evaluation of minimum bactericidal concentration (MBC). Furthermore, quantification of biomass and the number of viable cells in the biofilm were conducted, respectively, by staining with crystal violet and counting of colony forming units (CFU). The negative and positive controls used in all tests were, respectively, 4% DMSO and chlorhexidine gluconate adjusted according to the concentration data from the MIC of each micro-organism. The main constituents of the oil R. asperula were cariophylla-4 (12)-8-(13)-dien-5β-ol (14.1%), (E)-caryophyllene (22.7%) and caryophyllene oxide (29.4%) as (E)-caryophyllene (11.0%), spathulenol (13.1%) and δ-amorphene (14.9%) were the major constituents of oil R. paniculata. The data showed that the tested oils have had best results on the strains of Gram-positive bacteria, the essential oil of R. paniculata showed the best effect being able to inhibit planktonic growth, and the development of biofilms of S. oralis strain. Thus, the essential oils and R. asperula and R. paniculata emerge as important alternatives to control bacterial.