Óleo essencial de Ocotea lancifolia (schott) mez: influência de diferentes métodos de secagem do material vegetal e avaliação da atividade antifúngica

Abstract

Plants producing essential oils (EOs) are rich in secondary metabolites, which play an important role in their natural defenses against microorganisms. Among the microorganisms that cause economic losses in the forest sector are fungi. Ocotea lancifolia is a potential producer of EOs, with a wide range of possible bioactivities. The increasing use and demand for EOs, makes it necessary to optimize the processing of plant material to increase yield without changing organoleptic and chemical characteristics. Therefore, this dissertation aimed to determine the antifungal potential of O. lancifolia essential oil (EO) against wood decay fungi, and to verify its action on ergosterol content in the plasma membrane of phytopathogens. In addition, we sought to evaluate the influence of different drying methods on yield, density, organoleptic properties and chemical composition of the EOs of O. lancifolia leaves. To determine the antifungal potential of the EO, this, diluted in ethanol, was added to the nutrient medium BDA. The antifungal potential was verified against the white rot fungus Ganoderma applanatum and the brown rot fungus Lentinus lepideus. EO was evaluated at concentrations of 1.0; 1.5; 2.0 and 5.0 μL.mL-1, also considering ethanol at 1.0 μL.mL-1 (negative control) and propiconazole at 1.0 μL.mL-1 (positive control/ commercial fungicide). Through the analysis of the chemical composition of the EO the following were identified as major compounds: caryophyllene oxide (41.46%), -curcumen-15-al (17.05%) and Z-α-trans-Bergamotol ( 7.52%). For antifungal activity, the results showed that the EO inhibited the mycelium growth of the two fungal species, being this activity dependent on concentration. Mycelial growth index (MCI) was significantly affected at 1.5; 2.0 and 5.0 μL.mL-1 that did not differ statistically from the commercial fungicide. For L. lepideus species, the EO at a concentration of 5.0 μL.mL-1 caused fungicidal activity. In evaluations of the effect of EO on ergosterol content, a tendency to decrease its content was observed in both fungal species. Regarding the study on the influence of different drying methods, the processes of air drying, lyophilization, microwave and oven at 45 and 60ºC were used, on yield, density, color and chemical compounds of the EO OfO. lancifolia leaves by comparison with fresh leaf EO. It was found that microwave drying and lyophilization provided the highest yields, and the different methods did not affect the density of the extractive. For EOs submitted to the oven drying method at 45 and 60ºC, there was a drastic color change. The analysis of the chemical composition of the EO showed the caryophyllene oxide compound as the major in all EOs obtained after the drying processes, and that the other compounds were possibly influenced by time and temperature, resulting in differences in their chemical structure and / or percentage of compounds. Given the above, we highlight the potential of O. lancifolia EO as a growth inhibitor of the rotting fungi tested, as well as the potential of modern drying methods to provide OE in higher yield and without altering the organoleptic characteristics.