Óleos essenciais de Satureja montana L., Myristica fragrans H. e Cymbopogon flexuosus: extração, caracterização química e avaliação das atividades biológicas

Abstract

Currently, the use of essential oils with biological potential is gaining ground, being increasingly used in the cosmetics, pharmaceutical, food and agricultural industries. This study aimed to extract and chemically characterize the essential oils of three plant species, Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus, as well as to evaluate the antioxidant, fungicidal, bactericidal and repellent activities, inhibitory effect on acetylcholinesterase and to evaluate the effect of essential oils on the morphology of Escherichia coli and Staphylococcus aureus and fungi of the Aspergillus genus by means of Scanning Electron Microscopy (MEV). The essential oils were extracted by hydrodistillation, characterized and chemically quantified by Gas Chromatography coupled to Mass Spectrometry (CG / MS) and Gas Chromatography coupled to the Flame Ionization Detector (CG / FID). The effect of essential oils in inhibiting the AChE enzyme was evaluated by the rate of formation of the compound 5-thio-2-nitrobenzoate, produced from the reaction of Ellman's Reagent with thiocoline. The repellent effect was carried out protected from light, in an environment with controlled temperature and relative humidity: a circular paper filter was cut in half; in one half, 3% DMSO was used and, in another, the essential oil diluted in 3% DMSO in varying concentrations; then, six fasting adult ticks of the species Rhipicephalus sanguineus sensu lato were added to the center of the plate and their positions were evaluated after five minutes. The antibacterial potential against Escherichia coli and Staphylococcus aureus was assessed by tests of the cellular sensitivity test and by MEV analyzes. The evaluation of antioxidant activity was based on the DPPH radical stabilization tests, β- carotene bleaching and reducing power. The evaluation of the inhibitory effect of essential oils, the interference of the oils in the mycelial growth and in the inhibition of the ergosterol synthesis were tested on the species A. flavus (CCDCA 10508) and A. ochraceus (CCDCA 10506). The antiaflatoxigenic activity of essential oils was evaluated by inhibiting the biosynthesis of AFB1 and AFB2 of A. flavus in culture medium containing different concentrations of each essential oil. The anti-cratoxigenic activity of essential oils was evaluated by inhibiting OTA biosynthesis by the fungus Aspergillus ochraceus. The major components found in the essential oil of S. montana were borneol, γ-terpineol, carvacrol and p-cymene, the species M. fragrans presented sabinene, α-pinene and β-pinene and, in the composition of the essential oil of C. flexuosus, geranial and neral were found. In the inhibitory effect of aceltilcholinesterase, the essential oils that showed the greatest potential were S. montana and M. fragrans, with IC50 values close to 0.024 and 0.023 μg mL-1, respectively. The percentage of repellency with variable concentrations was higher for the essential oil of S. montana, reaching 60% repellency at the lowest concentration. However, in the test with constant concentration and variable time, the essential oil of S. montana and C. flexuosus proved to be effective up to 60 minutes after application. In the inhibitory and bactericidal effect, the essential oil of S. montana showed the same minimum and bactericidal concentration, 6.25 μL mL-1, on E. coli, and compared to S. aureus, the essential oil of C. flexuosus was more effective, presenting a CMI of 6.25 μL mL-1 and a CMB of 12.5 μL mL-1. The analyzes carried out in the MEV showed that the essential oils caused damage to the membrane and cell wall of the bacteria used. No essential oil showed a potential scavenger of DPPH• radicals; however, oils from S. montana and M. fragrans showed low potential in the β-carotene bleaching method with an IC50 of 45.50 μg mL-1 and 177.63 μg mL-1, respectively. In the reduction of iron, the essential oil of S. montana presented an inclination of 2.9 x 10-4, showing a potential to reduce iron ions in solution, whereas the essential oils of M. fragrans and C. flexuosus did not present such potential, as they presented less inclinations. The antifungal activity of essential oils was observed for all tested fungi. The essential oils under study showed good results in the tested concentrations, inhibiting mycelial growth, the production of ochratoxin A and aflatoxins B1 and B2 and the synthesis of ergosterol. A reduction in mycelial growth and ergosterol content was observed; therefore, the action of essential oils on the fungal plasma membrane is suggested.