Atividade antifúngica do óleo essencial de Lippia grata Schauer frente Candida albicans e dermatófitos

Abstract

Species of the genus Candida are responsible for about 80% of serious fungal infections, being Candida albicans the most commonly isolated species in these cases, and it is also frequently associated with cutaneous and mucocutaneous fungal infections. Among the filamentous fungi responsible for cutaneous mycoses in humans, dermatophytes, a group of crosely related fungi, affect 25% of the world population. In recent decades, both Candida and dermatophyte species have shown resistance to antifungal drugs. In this context, it is perceived an incessant search of the scientific community for molecular prototypes that present antifungal potential, such as those of plant origin, due to their many antimicrobial properties described in the literature. Therefore, the present proposal aims to evaluate the antifungal activity of the essential oil from the plant Lippia grata Schauer against Candida albicans and different species of dermatophyte fungi. The essential oil was obtained from the hydrodistillation process, with subsequent analysis of percentage content (%) and phytochemistry by gas chromatography associated with mass spectrometry. The bioactivity of the essential oil obtained from the Lippia grata plant was investigated on 26 fungal samples by determination of the Minimum Inhibitory Concentration (MIC) by broth microdilution and the Minimum Fungicidal Concentration (MFC) on solid media, while the synergistic activity was evaluated using the “checkerboard” method. The quantification tests of biofilm production and antibiofilm activity of Lippia grata essential oil were performed using crystal violet to measure the optical densities obtained. The yield of essential oil of Lippia grata was 2.45%. Four main phytoconstituents were identified in the chemical characterization of Lippia grata essential oil: carvacrol (51.4%) as the majority constituent, thymol (15.6%), ρ-cymene (12.2%) and γ-terpinene (7.4%). Antifungal activity of Lippia grata essential oil was found for 100% of the tested strains with MIC and MFC ranging from 390.62 μg/mL to 3.125 μg/mL against Candida albicans strains. For dermatophytes, the MIC ranged from 48.82 μg/mL to 390.62 μg/mL, while the MFC ranged from 48.82 μg/mL a 781.25 μg/mL. In addition, in the evaluation of CFM it was possible to observe that the oil showed fungicidal action against all the strains in the present study. Regarding the evaluation of the drug combination effect, synergistic (25%) and additive (75%) interaction was observed on the tested strains. The results for biofilm formation revealed that 100% of the strains were biofilm producers. For Candida albicans strains, 4 (22.22%) were weak producers, 5 (27.77%) moderate producers and 9 (50%) strong producers. For the dermatophyte strains, all were strong producers. For the antibiofilm activity of the essential oil (IC50%), it was verified biofilm inhibition ranging from 42.36% to 94.89% for Candida albicans and 29.94% to 88.42% for dermatophyte when these strains were post-treated with the CIM and 2xCIM concentrations of Lippia grata essential oil. For biofilm eradication (CMEB80%), it was noted that the concentrations tested were able to eradicate most of the biofilms in formation by the strains tested. It was concluded that the essential oil of Lippia grata showed high antifungal activity, motivating further studies with the aim of future development of phytopharmaceuticals for treatment of fungal infections.