Produção da fitomassa, análise fitoquímica e potencial citogenotóxico de tomilho (Thymus vulgaris L.)

Abstract

Thyme (Thymus vulgaris L.) has been attracting the interest of researchers for its wide use in the food and cosmetic industries, besides its use for medicinal purposes. The objective was to analyze the influence of the climatic seasons, winter and summer, and of different nitrogen concentrations, on the production of phytomass, yield and essential oil content of thyme, as well as to elucidate the chemical composition of the essential oil in both seasons, and to evaluate the potential cytotoxicity of both the aqueous extracts and the essential oil of the plants grown. The winter and summer experiments were conducted in a greenhouse from 2018 to 2020. Fresh and dry mass was evaluated to calculate phytomass production, and essential oil production was evaluated for yield and content. Liquid and gas chromatography was used to determine the chemical composition of the aqueous extracts and thyme essential oil, respectively. The Allium cepa test was employed to analyze the cytogenotoxic potential. The design used in the greenhouse experiment was entirely randomized, conducted in a factorial scheme (2X5), in two seasons of the year and five nitrogen concentrations in the nutrient solution (5, 7, 9, 11 and 13 mmol.L-1). All data were submitted to variance analysis. The data concerning phytomass production, yield and essential oil content were analyzed by Skott-Knott and polynomial regression. The data concerning the A. cepa test were compared by the Skott-Knott test. The data concerning the phytochemical analysis of the essential oil were submitted to multivariate statistics, with cluster analysis. The results showed that nitrogen, added to the nutrient solution, promoted an increase in the vegetative growth of thyme plants only when the temperature was high. The increase in phytomass promoted a higher essential oil yield. During the winter, the essential oil content was higher in the two treatments with the highest nitrogen doses. However, during the summer, there was no significant difference between the treatments with different nitrogen doses and the oil content. The aqueous extracts showed cytotoxic potential, by inhibiting cell division, and genotoxic potential, by observing chromosomal irregularities; the essential oil showed antiproliferative activity, but less intense, and also genotoxic activity by the A. cepa test. It was possible to detect gallic acid in a sample of thyme aqueous extract by liquid chromatography. Gas chromatography confirmed thymol as the major compound in thyme essential oil, at concentrations of 45.94% and 52.41% in summer and winter, respectively.