Composição química e atividade larvicida contra Aedes aegypti do óleo essencial da Eugenia calycina

Abstract

The study of bioactive compounds extracted from natural products has played an essential role in the recognition of new drugs with promising biological activities. These compounds can act as a reference standard for the synthesis of new substances or as active prototypes. The objective of this work was to identify an essential oil chemical composition (OE) of Eugenia calycina, to isolate compounds and to characterize it by spectroscopic techniques, to evaluate a larvicidal activity against Aedes aegypti and, finally, to evaluate a cytotoxic activity for Vero and HeLa. The OE was analyzed by gas chromatography coupled to a mass spectrometer (CG-MS), with oxygenated and non-oxygenated cyclic sesquiterpenes were identified as major constituents. The majority compounds were bicyclogermacrene (13.22%), spathulenol (15.98%) and β-caryophyllene (6.96%). The essential oil (400 mg) was fractionated in a chromatographic column and from the profile of the fractions by gas chromatography coupled to the flame ionization detector (GC-FID) was possible to identify the presence of three isolated compounds. These constituents were also analyzed by nuclear magnetic resonance (NMR) and their structures were identified as spathulenol (51.2 mg), 4β,10α-aromadendranediol (5.27 mg) and 1β,11-dihydroxy-5-eudesmene (7, 54 mg), the last two unpublished in the E. calycina. The larvicidal activity of the EO, was evaluated at 24, 48 and 72 hours and the LC50 obtained were 199.3±1,1; 166.4±1.2 and 148.3±1.1 μg mL-1, considered a promising activity. The isolated compounds were tested at 25 and 100 μg mL-1, but they were inactive. Through the results it can be observed that the longer the exposure time, the lower the amount of essential oil to kill 50 % of the A. aegypti larvae, decreasing the LC50. In addition, the compounds present in the EO act synergistically in the assessed activity. The cytotoxic concentration of EO for HeLa and Vero cells (266.8 ± 46.5 and 312.1 ± 42.5 μg mL-1, respectively) in 48 hours of exposure were higher than the LC50, showing low cytotoxicity at concentration that shows larvicidal activity, resulting in a positive selectivity index. Therefore, the leaves of E. calycina are shown as a very promising source of natural product in larvicidal activity.

Keywords: Eugenia calycina. Sesquiterpenes. Aedes aegypti. Isolated compounds.