RESUMO:Os óleos voláteis das folhas e infl orescências de Eupatorium polystachyum DC. (Asteraceae), coletado no Rio Grande do Sul, Brasil, foram caracterizados por CG-EM e sua atividade antioxidante foi avaliada utilizando-se o método de DPPH. Foram obtidos rendimentos de 1,6 e 0,9% de óleo em relação às folhas e infl orescências frescas, sendo identifi cados 34 compostos, correspondendo a 99,1 e 99,5% do óleo volátil, respectivamente. Os óleos apresentaram exclusivamente compostos terpênicos, sendo que as folhas contêm grande quantidade de monoterpenos (66,4%) enquanto que as infl orescências apresentaram quantidades equivalentes de mono e sesquiterpenos (51,8 e 47,7%, respectivamente). As amostras apresentaram-se qualitativamente muito semelhantes sendo constituídas majoritariamente por: β-pineno (14,7 e 9,8%), β-mirceno (15,3 e 10,8%) e limoneno (22,8 e 20,5%) entre os monoterpenos e β-cariofi leno (10,4 e 15,4%), germacreno D (7,2 e 9,4%) e biciclogermacreno (12,0 e 19,2%) entre os sesquiterpenos. As diferenças entre as amostras foram basicamente quantitativas. Os óleos apresentaram atividade antioxidante pelo ensaio com DPPH por bioautografi a na diluição de 1:10 em éter etílico (v/v). Unitermos: Eupatorium polystachyum, óleos voláteis, atividade antioxidante, DPPH.ABSTRACT: "Chemical composition and antioxidant activity of the volatile oil from Eupatorium polystachyum DC". The essential oil obtained from leaves and fl owers of Eupatorium polystachyum DC. (Asteraceae) collected in Rio Grande do Sul State, Brazil, was characterized by GC-MS and its antioxidant activity was assessed by DPPH assay. The yield of essential oil, relative to fresh material, was 1.6 and 0.9% for leaves and fl owers, respectively. Both oils are constituted exclusively by terpenic compounds. Leaf oil contains great quantity of monoterpenes (66.4%); on the other hand, infl orescence oil contains comparable quantities of mono-and sesquiterpenes (51.8 and 47.7%, respectively). The same compounds are majority in both oils: β-pinene (14.7 and 9.8%), β-myrcene (15.3 and 10.8%) and limonene (22.8 and 20.5%) among monoterpenes and β-caryophyllene (10.4 and 15.4%), germacrene D (7.2 and 9.4%) and bicyclogermacrene (12.0 and 19.2%) among sesquiterpenes. The oils had antioxidant activity by DPPH assay in 1:10 dilution in ethyl ether (v/v).

Investigating the influence of seasonal variations on biological activities is important for pharmacological studies and metabolic engineering. Therefore, this study was conducted to determine the variation of the chemical composition of essential oils obtained from Nectandra megapotamica leaves, collected at different stages of plant development, as well as its influence on the biological activities. A total of 38 compounds were identified that accounted for 97–99.2% of the chemical composition of the oils. Major differences were observed in the monoterpenic fraction, representing 5.1% of the compounds identified in the productive rest phase to 37.1% in the blooming phase. Bicyclogermacrene and germacrene D were the predominant compounds identified in the oil of all collections. Furthermore, limonene, β-pinene, and spathulenol were identified predominantly in the samples of blooming and fruiting phases. The oils exhibited significant antichemotactic activity and different effects in scavenging the radical 2,2-diphenyl-1-picrylhydrazyl. Variations were also observed in the antifungal activity, with the minimum inhibitory concentrations ranging from 125 to 500 μg/mL. These results demonstrate the influence of monoterpenes, primarily limonene, α-pinene, and β-pinene, on the bioactivities of the oil. Studies investigating the variations in the chemical composition of essential oil may offer a strategy to produce a compound or a group of compounds of interest to industries with a specific pharmacological focus.

The study demonstrates the promising application of Eryngium species as a source of potential central nervous system bioactive secondary metabolites, specially related to neurodegenerative disorders.

Eupatorium tremulum is a South American shrub reported to cause cattle digestive intoxication, of which the volatile oil, mainly composed by bisabolane- and amorphane-type sesquiterpenoids, exhibits high quantitative variability. This report describes the application of chemometric tools for the identification of volatile compounds that characterize phenophasical changes in the plant. Preblooming, blooming, and postblooming specimens were paired-sampled and submitted to hydrodistillation and GC-MS analysis. Differential results were analyzed by orthogonal projection to latent structures-discriminant analysis (OPLS-DA), and the substances with different distribution in each phase were highlighted. Mean results between phases were submitted to factor analysis (FA), and correlations between the variables were demonstrated. Preblooming to blooming phase change was characterized by decreased levels of amorpha-4-en-7-ol (13) and epi-α-bisabolol (19) and increased amounts of amorpha-4,7(11)-diene (1). Blooming to postblooming change was characterized by decreases in 1, germacrene D (2), and β-bisabolene (4) and increases in 13 and 19. Finally, enhanced levels of 1, 4, and 2 reflected the change from the postblooming to the preblooming phase. FA revealed a strong correlation in the variability between the bisabolane hydrocarbons, possibly related to its common enzymatic origin. Another strong source of negative correlation showed bisabolane- and amorphane-type alcohols, on one side, and amorphane-type furans, on the other side, to occur in two alternative oxidation routes. Finally, 1 was strongly negatively correlated to its oxidized furan and ketofuran derivatives [verboccidentafuran (16) and 3-oxo-verboccidentafuran (23)] and additionally to a third compound, putatively identified as a biosynthetic intermediate between this hydrocarbon and the furans, amorpha-4,7(11)-dien-8-one (20).

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The essential oil (EO) from leaves of Annona neosalicifolia H. Rainer (Annonaceae) obtained from two chemotypes in the southern Brazilian Atlantic Rainforest was analysed both by GC-FID and GC-MS. Forty compounds were identified, accounting for 95.9 to 99.5% of the total oil in each sample. The VOs were characterized by the predominance of sesquiterpenes in all samples, being main compounds bicyclogermacrene (13.9-41.8%) and beta-caryophyllene (9.3-26.3%); germacrene D was also found in high amounts, but its concentration was more variable. Monoterpene compounds were absent in the summer and fall samples, with higher concentrations in winter samples (6.1-7.4% for α-pinene and 6.4-11.2% for β-pinene). EO from chemotype II was characterized by a high concentration of the sesquiterpene alcohol (E)-nerolidol (36.3%), which was absent or in trace amounts in chemotype I. The characterization of these seasonal and individual variations in the chemical composition of the essential oil from A. neosalicifolia may have agronomical implications and may be important in the understanding and delimitation of the metabolic plasticity of the highly variable taxon A. emarginata as well.