Eugenia uniflora, known as the “Brazilian cherry”, is an economically important neotropical Myrtaceae in the cosmetics and pharmaceutical industries due the production of essential oils with antioxidant activity. On account of its significant genetic variability, genotype evaluations are needed in order to identify genetic features related to the essential oil production that meet the industry requirements. The main objective of the present study was to evaluate the yield, composition, and antioxidant activity of essential oils isolated from the leaves of 36 genotypes of E. uniflora. Essential oil samples were obtained by hydrodistillation, and their composition was determined by gas chromatography coupled with mass spectrometry. A variation of 0.22% to 1.68% in the essential oil yield was observed, in which 78 compounds, namely oxygenated sesquiterpenes, were identified. According to the cluster analysis of the major compounds, six groups were revealed. The observed diversity demonstrates the genetic variability of the species. Also, the antioxidant activity was affected by the composition of the essential oils, ranging from 176.66 to 867.57 µM TEAC.

HIGHLIGHTS Essential oils from populations of B. dracunculifolia were investigated. β-pinene and (E)-nerolidol were the main compounds in B. dracunculifolia populations. The difference in the chemical profile of the essential oils is quantitative only. There is a negative correlation between the antioxidant activity and spathulenol.

The essential oil produced by Eugenia uniflora leaves is intensively used by the cosmetic, pharmaceutic and perfumery industries mainly because its antioxidant effect and antimicrobial and antihelmintic ativities. Drying and storage of the aromatic plant leaves can affect the yield and quality of its essential oil. This study aimed to evaluate the effect of drying method and storage conditions on the essential oil yield and composition in Eugenia uniflora leaves. The essential oil were extracted from dried leaves at ambient temperature and at 45°C for six drying periods (0, 6, 24, 48, 72 and 96 hours-h). The essential oil yield was also analysed after 0, 60, 120, and 180 days of storage in three types of packaging. The oil was extracted by hydrodistillation and the composition was determined by gas chromatography-mass spectrometry. Results showed that drying the leaves at ambient temperature and 45°C for 48 and 24 h, respectively, increased the essential oil yield. At 45°C the monoterpene and sesquiterpene compounds increased, with curzerene+viridiflorene identified as the major compounds. Package types did not affect the essential oil yield but the increase of the storage period decreased it.

The present research deals with the collection and structural elucidation of an unknown component, accounting for about 35% of the essential oil obtained upon distillation of the leaves of Eugenia uniflora L., harvested during summer (January, 2017) in Paraná State (Southern Brazil). A multidimensional gas chromatographic preparative system, based on the coupling of three GC systems equipped with apolar, PEG and ionic liquid-based stationary phases, was successfully applied for the isolation of the chromatographic band relative to the unknown molecule. The use of wide-bore columns allowed for an increased sample capacity compared to conventional micro-bore columns, thus the injection of a neat sample was feasible, greatly reducing the total collection time. A higher chromatographic efficiency was afforded by the use of a multidimensional approach in the heart-cut mode, exploiting the different selectivity of three stationary phases, which ensured the attainment of a highly pure fraction. In only five runs, more than 3 milligrams were collected, with an average purity greater then 95%. Finally, the unknown component was subjected to nuclear magnetic resonance spectroscopy, mass spectrometry and condensed phase Fourier-transform infrared spectroscopy, leading to the identification of 6-ethenyl-6-methyl-3,5-di(prop-1-en-2-yl)cyclohex-2-en-1-one. The presented approach has been demonstrated to be effective for the isolation and structural elucidation of unknown molecules in complex samples, which will allow for further in-depth studies, like biological evaluation or pharmacological tests.

The aim of this study was to verify the seasonal influence on the Eugenia uniflora essential oils. The collections were carried out in October 2017 and March, May and August 2018. The extraction of the essential oils was performed by hydrodistillation and their composition was determined by gas chromatography. The yield of the essential oils was lower in winter (1.04% m/m). The composition of the essential oils in the different seasons did not change in relation to their compounds, differing only in their amounts. Germacrone was identified as the main compound, having a higher percentage in spring (48.05%) and summer (45.00%). Antioxidant activity (DPPH) may have been influenced by the higher percentages of germacrone, with better inhibitory concentration values (IC₅₀) in summer (0.62 mg/mL), followed by spring (0.98 mg/mL). The E. uniflora essential oils tested have moderate to weak antibacterial activity and were more efficient against Escherichia coli.