Óleo essencial de Nectandra grandiflora Nees & Mart. ex Nees: efeito antifúngico e bioestimulante em cultivos in vitro

Abstract

The present dissertation aims to contribute to correct knowledge of biological activities of Nectandra grandiflora Nees & Mart. ex Nees essential oil (EO) and its major compound, (+)-dehydrofukinone (DHF). So, the potential this extract was verified to act as biostimulant in native woody species explants cultivated in vitro. Additionally, the antifungal potential of both N. grandiflora OE and its major constituent against wood rot fungi was determined, as well as its action on ergosterol content in the plasma membrane of phytopathogens. The EO was obtained from N. grandiflora leaves by hydrodistillation with modified Clevenger apparatus. Then, extraction yield was determined, and chemical composition was analyzed by gas chromatography coupled to mass spectrometry (GC-MS). The major constituent of OE was isolated by 4 chromatographic columns, carried out in sequence. For tests with the explants, Eugenia involucrata De Candolle nodal segments were inoculated in ½ MS medium, supplemented with N. grandiflora EO, previously diluted in ethanol, at .0.00, 0.05, 0.075, 0.1, 0.125, 0.15, 0.175 e 0.2 μL mL-1. The results showed that, when exposed to EO at 0.075 μL mL-1, the explants emitted a greater number of leaves when compared to the controls. For determination of N. grandiflora OE and its major constituent antifungal potential, the extractives previously diluted in ethanol were added to PDA medium. The antifungal potential was verified against white-rot fungi Ganoderma applanatum (Pers.) Pat. and Trametes versicolor (L.: Fr) Pilát, as well as brown-rot fungi Lentinus lepideus (Fr.) Fr. and Gloeophyllum trabeum (Pers.: Fr) Murrill. The EO was evaluated at 0.0, 0.5, 1.0 and 2.0 μL mL-1, whereas DHF was evaluated at the corresponding concentration to that found in 0.5 μL mL-1 EO (0.0971 μL mL-1). Regarding the results of mycelium growth inhibition, N. grandiflora EO completely inhibited growth of white-rot fungi T. versicolor, at 1.0 μL mL-1 EO, presenting the same behavior as positive control. The other fungal species did not have their growth affected by the extractives at the tested concentrations. Additionally, the results for the EO treatments did not differ from those obtained with the isolated substance, evidencing that the DHF is one of the substances responsible for the antifungal activity detected. Regarding the influence of the extractives on ergosterol content in plasma membrane of phytopathogens, the results indicated that both extractives evaluated caused a reduction of this sterol in T. versicolor and G. applanatum, indicating that their action target was the plasma membrane of whiterot fungi. Thus, the potential of N. grandiflora EO to act as possible biostimulant in the development of in vitro nodal segments of E. involucrata is highlighted, as well as to inhibit the growth of white-rot fungus T. versicolor.