Avaliação antimicrobiana de óleos essenciais e sua capacidade antioxidante em ensaios in vitro

Abstract

Scientific studies have revealed the potential human health risks associated with excessive use of antibiotics, preservative additives and pesticides. The indiscriminate use of antibiotics favors the emergence of resistant microorganism to these drugs. Conservative additives if ingested in high amounts may be cytotoxic. The studies concerning the agrotoxics generate an infinite discussion, revealing the mutagenic, carcinogenic and teratogenic capacity. The essential oils of plants has been used as an alternative to the use of antibiotics, mainly, by the facility of being found and extracted. In this sense, the objective of this work is to evaluate in vitro if the compounds present in Cymbopogon winterianus (citronela), Pogostemon cablin (patchouli), Eugenia uniflora (pitanga), Melaleuca anternifolia Cheel (melaleuca), Casearia sylvestris Swartz (guaçatonga) e Lavandula angustifolia Miller (lavanda) have antibacterial, antioxidant activities. The essential oils were obtained from the leaves of this plants by the process of hydrodistillation and the composition was determinate utilizing a Gas-chromatograph coupled to a Mass spectrometer. The antibacterial potential of the oils were established through of the microdilution method in plates to determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (CBM). The effect on the bacterial growth curve was carried out by means of a Mueller Hinton broth bioassay with concentration initial of the equivalents oils the MIC, the concentrations of bacterial were determinate and adjusted in spectrophotometer in absorbance 0.08 with D.O625 of 1.5x108 CFU mL-1, in triplicates the bacterial concentration was measured in time 0, 2, 4, 8 and 12 hours. The antioxidant action was evaluated by the ability of the oil to sequester the radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH). A total of 53 different compounds were identified in the tested oils, with 1,8-cineol being 72,31%, β-citronellal 34,15% and pacholol 21,99%. Only three compounds, 1,8-cineole, σ-amorphene and γ-morulene, were identified in more than one oil. As regards by antibacterial effect, the pitanga essential oil presented better inhibitory activity for the E. coli with MIC of 1,49 mg mL-1, melaleuca oil had better bactericidal activity with CBM of 5,67 mg mL- 1. The pitanga oil in the S. enterica bacterium, with MIC values 2,98 mg mL-1 and MBC 5,98 mg mL1, for S. aureus citronella oil was more effective with 2,63 mg mL-1 MIC and 5,27 mg mL-1 MBC, similar results were obtained on growth curve graphs. The essential oil of citronella presented the best result 660,48μmol TE mL-1, and the oil of melaleuca did not record oxidant activity. The results obtained point to the potential use of essential oils in products with antioxidant properties, as well as antibiotic adjuvants.