Estudo fitoquímico e avaliação da atividade antimicrobiana das folhas de Varronia dardani (Taroda) J.S. Mill (Boraginaceae) e de seu óleo essencial

Abstract

The genus Varronia belongs to the family Boraginaceae, previously classified as Cordia, comprises about 100 species. Some species are described in the literature with activities anti-inflammatory, analgesic and cicatrizant. The species Varronia dardani has no reports in folk medicine. The vegetal material was collected in Serra Branca - PB, a voucher specimen is deposited in the Prof. Lauro Pires Xavier herbarium under registration JPB 29509. The leaves from V. dardani were dried in an oven at 40 oC, crushed and extracted with 95% ethanol, concentrated in a rotavaporator, obtaining the Ethanolic Crude Extract (ECE), which was degreased with hexane and then partitioned liquid/liquid (7: 3 v / v) to give the hexane, dichloromethane, ethyl acetate and n-butanol phases. The chemical structures were identified by mass spectroscopy, Nuclear Magnetic Resonance (NMR) and in comparisons from the literature. The dichloromethane phase (Vd-DP) was subjected to medium pressure liquid chromatography from which six substances were isolated, two chalcones (pinostrobin chalcone and gymnogrammene) and four flavanones (pinocembrin, isosakuranetin, pinostrobin and sakuranetin-4'-methyl ether). The essential oil from leaves of V. dardani (Vd-EO) was extracted by hydrodistillation by using a Clevenger apparatus and characterized by gas chromatography coupled to mass spectrometry (GC-MS). The chemical composition of V. dardani oil was 97.2% monoterpenes and sesquiterpenes. The d-Cadinene (8.71%), thymol (7.43%), carvacrol (5.92%), ?-cadinene (5.66%), p-cymene (5.25%) and d- cadinol (5.20%) was the major constituents. Antimicrobial activity was investigated by the Minimum Inhibitory Concentration (MIC) and the Inhibition of Biofilm Formation (IBF), performed by microdilution and using the ECE, its dichloromethane phase, the Vd-EO and some flavanones and chalcones isolated and/or in mixtures with species of microorganisms of interest in dentistry. The essential oil inhibited the growth of Enterococcus faecalis and Streptococcus salivarius with MIC of 2 mg/mL, Vd-ECE inhibited the growth of S. salivarius, Vd-DP exhibited a MIC against strains of E. faecalis and S. salivarius, pinostrobin chalcone inhibited the growth of S. salivarius, and in combination with gymnogrammene, showed a MIC for strains E. faecalis and S. salivarius. Pinocembrin inhibited the growth of E. faecalis and S. salivarius. Pinocembrin, pinostrobin chalcone and its mixture with gymnogrammene showed inhibition of the formation of S. salivarius biofilm in the highest concentration tested. Pinostrobin chalcone inhibited the formation of the E. faecalis biofilm at its lowest concentration. The in vitro results indicated that the species contains in its chemical composition substances with antimicrobial potential, thus requiring complementary studies aiming to seek a new therapy for dental infections using the species cited.