Studies on the antimicrobial activity and brine shrimp toxicity of Zeyheria tuberculosa (Vell.) Bur. (Bignoniaceae) extracts and their main constituents

<p>Abstract</p> <p>Background</p> <p>Due to the indiscriminate use of antimicrobial drugs, the emergence of human pathogenic microorganisms resistant to major classes of antibiotics has been increased and has caused many clinical problems in the treatment of infectious diseases. Thus, the aim of this study was to evaluate for the first time the <it>in vitro </it>antimicrobial activity and brine shrimp lethality of extracts and isolated compounds from <it>Zeyheria tuberculosa </it>(Vell.) Bur., a species used in Brazilian folk medicine for treatment of cancer and skin diseases.</p> <p>Methods</p> <p>Using the disc diffusion method, bioautography assay and brine shrimp toxicity test (<it>Artemia salina </it>Leach), we studied the antimicrobial activity and lethality of extracts and isolated compounds against three microorganisms strains, including Gram-positive (<it>Staphylococcus aureus</it>) and Gram-negative (<it>Pseudomonas aeruginosa</it>) bacteria and yeasts (<it>Candida albicans</it>).</p> <p>Results</p> <p>In this study, the extracts inhibited <it>S. aureus </it>(8.0 ± 0.0 to 14.0 ± 0.0 mm) and <it>C. albicans </it>(15.3 ± 0.68 to 25.6 ± 0.4 mm) growth. In the brine shrimp test, only two of them showed toxic effects (LC₅₀29.55 to 398.05 μg/mL) and some extracts were non-toxic or showed weak lethality (LC₅₀705.02 to > 1000 μg/mL). From these extracts, four flavones [5,6,7,8-tetramethoxyflavone (1), 5,6,7-trimethoxyflavone (2), 4'-hydroxy-5,6,7,8-tetramethoxyflavone (3), and 4'-hydroxy-5,6,7-trimethoxyflavone (4)] were isolated through bioassay-guided fractionation and identified based on the 1D and 2D NMR spectral data. By bioautography assays, compounds 1 [<it>S. aureus </it>(16.0 ± 0.0 mm) and <it>C. albicans </it>(20.0 ± 0.0 mm)] and 3 [<it>S. aureus </it>(10.3 ± 0.6 mm) and <it>C. albicans </it>(19.7 ± 0.6 mm)] inhibited both microorganisms while 2 inhibited only <it>S. aureus </it>(11.7 ± 0.6 mm). Compound 4 did not restrain the growth of any tested microorganism.</p> <p>Conclusion</p> <p>Our results showed that extracts and isolated flavones from <it>Z. tuberculosa </it>may be particularly useful against two pathogenic microorganisms, <it>S. aureus </it>and <it>C. albicans</it>. These results may justify the popular use this species since some fractions tested had antimicrobial activity and others showed significant toxic effects on brine shrimps. However, in order to evaluate possible clinical application in therapy of infectious diseases, further studies about the safety and toxicity of isolated compounds are needed.</p

A Volatile Semiochemical Released by the Fungus Garden of Leaf-Cutting Ants

Made available in DSpace on 2020-12-10T19:55:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The symbiosis between fungi and leaf-cutting ants (Hymenoptera: Formicidae) has aroused the interest of researchers about the mechanism used by ants to select plants. The nutritional needs of the fungus garden, and the absence of potentially deleterious substances from plants, are criteria for selection by foraging workers. This is supported by behavioral experiments using fungicide with baits (citrus pulp) or forage plants highly accepted by leaf-cutting ants. The fungus garden is hypothesized to emit a volatile semiochemical in response to a fungicide, which informs ants that a plant is unsuitable for its growth. The objectives of our study were to identify the volatile compounds released by the fungus garden of leaf-cutting ants in response to a fungicide, as well as to determine the behavioral response of workers to healthy and unhealthy fungus gardens. The results showed no difference in the proportion of volatile compounds released by either healthy or unhealthy fungus gardens. Analysis of the responses of ants to healthy or unhealthy fungus gardens in a dual-choice experiment revealed a strong attraction to the fungus garden, regardless of its health status. We therefore conclude that no volatile semiochemicals are emitted by the fungus garden due to the action of deleterious substances. Univ Estadual Sao Paulo, Dept Protecao Vegetal, Lab Insetos Sociais Praga, UNESP, Botucatu, SP, Brazil Univ Estadual Sao Paulo, Fac Ciencias Agron, Lab Cent, UNESP, Botucatu, SP, Brazil Univ Oeste Paulista UNOESTE, Coll Agr Sci, Agron Dept, Lab Agr Entomol, Presidente Prudente, SP, Brazil Univ Estadual Sao Paulo, Dept Protecao Vegetal, Lab Insetos Sociais Praga, UNESP, Botucatu, SP, Brazil Univ Estadual Sao Paulo, Fac Ciencias Agron, Lab Cent, UNESP, Botucatu, SP, Brazil CNPq: 301718/2013-

Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon

The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT