This study evaluated the influence of seasonal variation on the yield and composition of essential oil of Lippia origanoides occurring in the Middle Rio Amazonas, Brazil, and the impact on its antimicrobial potential. The average oil yield was 1.7% ± 0.2% in the rainy season and 1.6% ± 0.3% in the dry season. Some correlations with climatic parameters were observed. The major components were carvacrol (rainy, 43.5% ± 1.9%; dry, 41.4% ± 2.04%), thymol (rainy, 10.7% ± 1.1%; dry, 10.6% ± 0.9%), p-cymene (rainy, 9.8% ± 0.7%; dry, 10.0% ± 1.4%) and p-methoxythymol (rainy, 9.6% ± 0.8%; dry, 10.4% ± 1.4%). It was found that the antibacterial activity of L. origanoides against Staphylococcus aureus and Escherichia coli was little influenced by the changes in oil composition due to seasonal variation. Against S. aureus, the oil Minimum Inhibitory Concentration (MIC) value was 1.25 μL/mL over ten months. Against E. coli, the oil MIC values ranged from 0.15 μL/mL to 0.31 μL/mL in different months of the year. The Minimum Bactericidal Concentration (MBC) value was 2.5 μL/mL against S. aureus and 1.25 μL/mL against E. coli. The results suggest that the antimicrobial activity identified in the oil remain unchanged for the full year, allowing its medicinal use without any risk of loss or absence of the active principles of the plant.

ResumoEntre as várias espécies que possuem ampla diversidade para atividades biológicas, estão as da família Myrtaceae, que apresentam alto teor de óleo essencial. Em virtude da carência de estudos com atividade antioxidante do gênero Myrcia (Myrtaceae), o objetivo deste trabalho foi avaliar a capacidade antioxidante do óleo essencial de folhas frescas de Myrcia sylvatica (OEMS) por meio dos métodos de captura de radical livre (DPPH e ABTS) e pela auto-oxidação do FRAP e do sistema β-caroteno/ácido linoleico, comparando a padrões trolox e BHA como referências. A capacidade antioxidante pelo método DPPH apresentou IC50 de 1,94 ± 0,12 mg/mL em 60 minutos de reação. Pelo método ABTS, apresentou atividade antioxidante correspondente a 32,85 ± 0,86 µM de trolox/g de OEMS. Pelo método FRAP apresentou Z de 193,47 ± 2,63 de µM de sulfato ferroso/g de OEMS, em 45 minutos de reação. No teste de β-caroteno/ácido linoleico, o OEMS (4 mg/mL) inibiu 26,1% da oxidação do β-caroteno em 120 min de reação. O óleo essencial de M. sylvatica apresentou baixa atividade antioxidante, sendo pouco eficaz comparativamente às referências, mesmo que testado por mais de um mecanismo. Palavras-chave: Atividade antioxidante. Óleo essencial. DPPH. ABTS. FRAP. β-caroteno/ácido linoleico. Myrcia sylvatica. 118 Revista Fitos. Rio de Janeiro. 2018; 12(2): 117-126 | e-ISSN: 2446-4775 | www.revistafitos.far.fiocruz.br Atividade antioxidante do óleo essencial de Myrcia sylvatica (G. Mey.) DC. por diferentes métodos de análises antioxidantes (ABTS, DPPH, FRAP, β-caroteno/ácido linoleico) AbstractAmong the various species that possess wide diversity for biological activities, are those from the Myrtaceae family, which have high content of essential oil. Due to the lack of studies with Myrcia (Myrtaceae) antioxidant activity, the aim of this work was to evaluate the antioxidant capacity of essential oil from fresh leaves of Myrcia sylvatica (OEMS) by free radical capture methods (DPPH and ABTS) and by autoxidation of the FRAP and the β-carotene/linoleic acid system, comparing trolox and BHA standards as references. The antioxidant capacity by the DPPH method showed IC 50 of 1.94 ± 0.12 mg/mL in 60 minutes of reaction. By the ABTS method, OEMS presented antioxidant activity corresponding to 32.85 ± 0.86 μM trolox/g. By the FRAP method, Z showed 193.47 ± 2.63 μM of ferrous sulfate/g of OEMS in 45 minutes of reaction. In the βcarotene/linoleic acid test, the OEMS (4 mg/mL) inhibited 26.1% of β-carotene oxidation in 120 min of reaction. The essential oil from M. sylvatica presented low antioxidant activity, being less effective compared to the references, even when it was tested by more than one mechanism. IntroduçãoAntioxidantes são substâncias que retardam a velocidade da oxidação, quando ocorre a produção excessiva de radicais de oxigênio durante processos patofisiológicos ou devido a fatores ambientais (1) .Através de um ou mais mecanismos, os antioxidantes têm como função reduzir a oxidação, como por exemplo, por meio da inibição de radicais livres e co...

The emergence of fungal resistance to commercial drugs has been a major problem for the WHO. In this context, research with natural products is promising in the discovery of new active substances. Thus, this work evaluated the antifungal effect of a medicinal plant (i.e., Mesosphaerum suaveolens) against strains of the genus Candida, tested the combined effect with the drug fluconazole, and, finally, determined the phenolic constituents present in the species. Initially, aqueous extracts of leaves (AELMs) and aerial parts (AEAPMs) of the species were prepared. For microbiological assays, the minimum fungicidal concentration was determined by broth microdilution, and the combined effect of fluconazole extracts were verified by sub-inhibitory microdilution concentrations (CFM/8) followed by spectrophotometric readings which were used to determine the IC50. HPLC detected the presence of flavonoids and phenolic acids, detecting eight compounds present in the samples of which caffeic acid and quercetin were major components. The AELMs modulated fluconazole activity since it decreased fluconazole’s IC50 from 7.8 µg/mL to an IC50 of 4.7 µg/mL (CA LM 77) and from 28.8 µg/mL to 18.26 µg/mL (CA INCQS 40006) for the C. albicans strains. The AEAPMs were able to potentiate the effect of fluconazole more effectively than the AELMs. Such an effect was significant for the 16 µg/mL concentration for CA LM 77 and 32 µg/mL for CA INCQS 40006. The AEAPMs as well as the AELMs presented clinically relevant activities for C. tropicalis strains. For the C. tropicalis LM 23 strain, the AEPMs obtained an IC50 of 25 µg/mL and the AELMs an IC50 of 359.9 µg/mL.