Cíntia Alvarenga Santos Fraga de Miranda

Óleos essenciais de folhas de diversas espécies: propriedades antioxidantes e antibacterianas no crescimento espécies patogênicas

Essential oils can be employed in the food, drinks, toiletry and cosmetics industries to prevent or reduce lipid deterioration and contamination by microorganisms. The aim of this work was to evaluate the functional antimicrobial and antioxidant properties of essential oils of fresh leaves from Coniza bonariensis, Parthenium hysterophorus, Tithonia diversifolia, Ambrosia polystachya, Hedychium coronarium and Baccharis dracunculifolia, extracted by hydrodistillation. The methodologies used for assessing antioxidant potential were consumption of the DPPH radical and oxidation inhibition of the β-carotene/linoleic acid system. Sensitivity of the bacteria Salmonella cholerasuis, Listeria monocytogenes, Staphylococcus aureus and Escherichia coli to the essential oils was determined using the agar-well diffusion method. The essential oils were noteworthy for their high terpenoid content. None of the essential oils assessed by DPPH radical sequestration presented significant IC50. Using β-carotene/linoleic acid methodology, the essential oils of T. diversifolia and H. coronarium showed no significant activity, and C. bonariensis, P. hysterophorus, A. polystachya and B. dracunculifolia showed IC50 greater than the highest concentration evaluated. The essential oils of C. bonariensis, T. diversifolia, H. coronarium and B. dracunculifolia displayed antibacterial activity for gram-negative and grampositive bacteria, with the exception of the volatile oil of P. hysterophorus, which did not inhibit growth in any of the bacterial strains tested. The essential oil of A. polystachya displayed antibacterial activity only for strains of S. aureus.

Clotting and fibrinogenolysis inhibition by essential oils from species of the Asteraceae family

Essential oils are pharmacologically active and unexplored compounds. The inhibitory properties of essential oils from Baccharis dracunculifolia, Conyza bonariensis, Tithonia diversifolia and Ambrosia polystachya were evaluated in the coagulation and fibrinogenolysis induced by snake venoms. The essential oil from Conyza bonariensis extended the clotting time of Lachesis muta from 52.2 to 115.2 seconds and that of Bothrops moojeni from 108.3 to 2340.0 seconds, when pre-incubated with the venoms. The longest clotting times for Bothrops atrox venom were observed after incubation with the essential oils from Conyza bonariensis and Tithonia diversifolia: the times increased from 100.8 to 264.0 and 227.7 seconds, respectively. The prior incubation of the essential oils with plasma and subsequent addition of Lachesis muta venom resulted in a pro-clotting effect. The oils from Ambrosia polystachya and Baccharis dracunculifolia caused 100% of inhibition on the fibrinogenolysis induced by Bothrops moojeni and Lachesis muta venoms (the oils were previously incubated with the venom). The results indicate that the essential oils show promise as adjuvants for the treatment of snakebites.

Chemical analyses of the essential oils from leaves of Mikania glauca Mart. ex Baker

The essential oils obtained by hydrodistillation of two samples of fresh Mikania glauca leaves collected in different periods were analyzed by gas chromatography (GC) and by GC–mass spectrometry (GC–MS). Twenty compounds, representing 99% of the total oil composition, were identified and quantified in sample 1, while forty-five compounds, also representing 99% of the total oil composition, were identified in sample 2. The essential oils from the fresh leaves of both samples were rich in the terpenes. In sample 1 and 2, respectively, α-pinene (27% and 26%), β-pinene (22% and 36%), myrcene (24% and 18%), β-caryophyllene (9% and 6%) and bicyclogermacrene (8% and 4%) were the principal constituents. This demonstrated the predominance of monoterpene hydrocarbons in the essential oil of M. glauca and the influence of the collection period on the concentrations of the components.

Chemical characterisation and allelopathic potential of essential oils from leaves and rhizomes of white ginger

Essential oils have the potential to be used as bioherbicides, and possess the advantage of their biodegradability, high structural diversity and reduced natural resistance to weeds. The essential oils of the leaves and rhizomes of Hedychium coronarium, an exotic invasive plant adapted to different regions of Brazil, were extracted by hydrodistillation and characterised chemically by Gas-Liquid Chromatography and Gas-Liquid Chromatography/Mass Spectrometry. Allelopathic activity was determined using methodologies that evaluate the effects of volatility and direct contact on seed germination and seedling vigour in the lettuce. The major constituents of the essential oil from the leaves were β-pinene (46.9%), α-pinene (19.2%) and β-caryophyllene (13.2%) and from the rhizomes, β-pinene (41.5%), 1.8-cineole (23.6%) and α-pinene (13.1%). When analysing the volatile effects of the essential oils, it was seen that their concentration did not affect seedling first germination count or total germination. The essential oil from the rhizomes was more effective than the essential oil from the leaves in reducing seedling response for SGI, dry weight, and length of the roots and shoots. When evaluating the effect of direct contact with the essential oils, it was seen that both oils reduced the response of all the variables under evaluation, and that in addition, the oil from the rhizomes caused greater reductions than that from the leaves, again for all variables. These results can be attributed to the higher levels of monoterpenes present in the essential oil from the rhizomes, mainly the presence of 1.8-cineole.