Óleos essenciais de espécies nativas de Myrtaceae: caracterização química e atividades antioxidante, antimicrobiana e citotóxica

Abstract

Plant species are of great importance in the discovery of bioactive compounds with antioxidant and biological activities. Despite the great potential that natural products obtained from the Myrtaceae family have, a considerable number of native species of this group have not yet been studied in depth. In this sense, this study aimed to evaluate the chemical composition and antioxidant, antimicrobial and cytotoxic activities of essential oils from four Atlantic Rain Forest native Myrtaceae species including Myrcia oblongata, Myrcianthes gigantea, Myrciaria tenella and Eugenia uniflora (essential oil of reference). The extraction of essential oils was carried out from fresh leaves, by hydrodistillation, using Clevenger's apparatus. The chemical composition was performed using Gas Chromatography associated with Mass Spectrometry technique. The antioxidant potential was studied through the DPPH and ABTS radicals capture methodologies, the evaluation of the reducing power via FRAP and the quantification of total phenolic compounds. The evaluation of the antimicrobial activity was performed against pathogenic microorganisms through the determination of the Minimum Inhibitory Concentration (MIC), as well as the evaluation of the bactericidal and fungicidal activities. Cytotoxicity on human tumor cell line was evaluated using the cell viability assay. The extraction yields obtained were from 0.015% to 0.817%, and the chemical composition revealed the predominance of terpenic compounds, including α and β-pinene, D-limonene, O-cymene, β and γ-Elemene, β-Caryophyllene and curzerene. The best antioxidant potential was evidenced for E. uniflora essential oil by the DPPH, ABTS, FRAP and EC50 tests, followed by M. tenella (DPPH and EC50) and M. gigantea (ABTS). The best antimicrobial potentials were obtained, respectively, for M. tenella, M. gigantea, E. uniflora and M. oblongata, with a broad spectrum of inhibitory activity reached on Gram-positive and negative bacteria, yeast and pathogenic filamentous fungus. Bactericidal and fungicidal effects were observed, with emphasis on M. tenella, which presented the largest spectrum of biocidal activity, including Escherichia coli, Listeria monocytogenes, Salmonella enterica Typhimurium and Candida albicans (0.39 mg/mL). The cytotoxicity test on the human adrenocortical carcinoma lineage (H295R lineage) revealed that all essential oils tested had a cytotoxic effect, with the lowest inhibitory concentrations being obtained for M. gigantea and E. uniflora (EC50 of 316.52 and 322.93 µg/mL, respectively), followed by M. tenella and M. oblongata (EC50 of 414.71 and 440.73 µg/mL), demonstrating antiproliferative potential. In conclusion, a remarkable chemical diversity of organic compounds was found among the essential oils of native Myrtaceae species, with antioxidant, antimicrobial and cytotoxic activities, listing such species as promising sources of bioactive compounds.