Avaliação do perfil químico do óleo essencial de quimiotipos de Lippia origanoides Kunth obtidos em diferentes coletas ao longo do dia e sua atividade biológica

Abstract

Lippia origanoides Kunth (Verbenaceae) is a shrub widely distributed in savanna areas in the state of Roraima (Brazil). The quantitative and qualitative variations of the constituents and biological activities of the essential oil of several species of the genus Lippia have been studied, with noted success. This study aims to evaluate the chemical profile of the essential oil of chemotypes from Lippia origanoides and determine its biological activity. To perform the analyses, material was collected from two L. origanoides individuals initially named individual A and individual B, located in the city of Boa Vista, the margins of highway BR 174, at Km 517, at three different times (8am, 12am and 6pm) in May and June 2013. The oils were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry. The identification of essential oil components was performed with the aid of standards, Kovats index, digital libraries and comparison with the literature data. For the determination of antioxidant activity, free radical DPPH sequestration and co-oxidation of β-carotene/Linoleic acid system methods were used. The chromatographic profile of the oils of the two individuals showed significant differences at all collection times, and thus the existence of chemotypes for the species collected in this region was determined, with Caryophyllene being the major constituent, obtained from the Chemotype A individual, while the major constituent carvacrol was obtained from chemotype B. In chemotype A, during the three collection times, E-caryophyllene was supplied with content ranging from 17.91 to 23.92%, followed by bisabolol oxide from 10.43 to 12.57%. In chemotype B, carvacrol showed a small variation range from 32.52 to 37.41% along the day in both periods of collection. In the antioxidant evaluation of chemotypes, it was observed that chemotype B presented higher activity, since the IC50 value was 0.045 mg/mL while chemotype A supplied an IC50 value of 2.2 mg/mL. By the method of oxidation of β-carotene/linoleic acid system, the percentage of chemotype B activity was better and closer to the synthetic antioxidant BHT, thereby inhibiting the oxidation of β-carotene. As for antimicrobial activity, good results were not obtained, since the values of the minimum inhibitory concentration (MIC) were elevated compared to the standard antimicrobial used. With these results it can be inferred that the Lippia origanoides has potential for use as a natural antioxidant, being important to monitor the essential oil production in order to obtain oil rich in its active principles.