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排序方式: 共有1027条查询结果,搜索用时 15 毫秒
21.
Luiz A. F. Coelho Jos V. Oliveira Saul G. D'vila Janete H. Y. Vilegas Fernando M. Lanas 《Journal of separation science》1997,20(8):431-436
The effects of temperature and solvent density on the characteristics of the extracts obtained from supercritical fluid extraction (SFE) of the volatile compounds from Brazilian rosemary (Rosamarinus officianalis L., Labiatae) using carbon dioxide (CO2) as solvent were investigated. The experiments were performed in a semi-batch laboratory scale home-made unit at two temperatures, viz. 310.15 and 320.15 K, over the pressure range of 100-160 bar. This study allowed to determine the crossover point and the maximum solubility of the oil. The products were analyzed by HRGC-MS, and compounds grouped in three different classes according to their molecular mass distribution in order to evaluate the influence of the variables studied on the characteristics of the extracts. The model proposed by Sovová was adopted in an attempt to interpret the mass transfer phenomena in the extraction process. 相似文献
22.
Thierry Wesley de Albuquerque Aguiar Jos Josenildo Batista Silvio Assis de Oliveira Ferreira Maíra de Vasconcelos Lima Sampaio Dewson Rocha Pereira Magda Rhayanny Assuno Ferreira Luiz Alberto Lira Soares Ana Maria Mendona de Albuquerque Melo Mnica Camelo Pessoa de Azevedo Albuquerque Andr de Lima Aires Hallysson Douglas Andrade de Araújo Luana Cassandra Breitenbach Barroso Coelho 《Molecules (Basel, Switzerland)》2022,27(15)
Biomphalaria glabrata snails constitute the main vector of schistosomiasis in Brazil, and Bauhinia monandra Kurz, the leaves of which contain BmoLL lectin with biocidal action, is a plant widely found on continents in which the disease is endemic. This work describes the composition of B. monandra preparations and the effect on embryos and adult snails, their reproduction parameters and hemocytes. We also describe the results of a comet assay after B. glabrata exposure to sublethal concentrations of the preparations. Additionally, the effects of the preparations on S. mansoni cercariae and environmental monitoring with Artemia salina are described. In the chemical evaluation, cinnamic, flavonoid and saponin derivatives were detected in the two preparations assessed, namely the saline extract and the fraction. Both preparations were toxic to embryos in the blastula, gastrula, trochophore, veliger and hippo stages (LC50 of 0.042 and 0.0478; 0.0417 and 0.0419; 0.0897 and 0.1582; 0.3734 and 0.0974; 0.397 and 0.0970 mg/mL, respectively) and to adult snails (LC50 of 6.6 and 0.87 mg/mL, respectively), which were reproductively affected with decreased egg deposition. In blood cell analysis, characteristic cells for apoptosis, micronucleus and binucleation were detected, while for comet analysis, different degrees of nuclear damage were detected. The fraction was able to cause total mortality of the cercariae and did not present environmental toxicity. Therefore, B. monandra preparations are promising in combating schistosomiasis since they can control both the intermediate host and eliminate the infectious agent, besides being safe to the environment. 相似文献
23.
Ellen de Nazar S. da Cruz Luana de Sousa Peixoto Jamile S. da Costa Rosa Helena V. Mouro Walnice Maria O. do Nascimento Jos Guilherme S. Maia William N. Setzer Joyce Kelly da Silva Pablo Luis B. Figueiredo 《Molecules (Basel, Switzerland)》2022,27(8)
Eugenia patrisii Vahl is a native and non-endemic myrtaceous species of the Brazilian Amazon. Due to few botanical and phytochemical reports of this species, the objective of the present work was to evaluate the seasonal variability of their leaf essential oils, performed by GC and GC-MS and chemometric analysis. The results indicated that the variation in oil yields (0.7 ± 0.1%) could be correlated with climatic conditions and rainy (R) and dry seasons (D). (E)-caryophyllene (R = 17.1% ± 16.0, D = 20.2% ± 17.7) and caryophyllene oxide (R = 30.1% ± 18.4, D = 14.1% ± 19.3) are the major constituents and did not display significant differences between the two seasons. However, statistically, a potential correlation between the main constituents of E. patrisii essential oil and the climatic parameters is possible. It was observed that the higher temperature and insolation rates and the lower humidity rate, which are characteristics of the dry season, lead to an increase in the (E)-caryophyllene contents, while lower temperature and insolation and higher humidity, which occur in the rainy season, lead to an increase in the caryophyllene oxide content. The knowledge of variations in the E. patrisii essential oil composition could help choose the best plant chemical profile for medicinal purposes. 相似文献
24.
Ohne ZusammenfassungMit 5 Abbildungen. 相似文献
25.
Beltrão EI Correia MT Figueredo-Silva J Coelho LC 《Applied biochemistry and biotechnology》1998,74(3):125-134
The phenomenon of altered carbohydrates in transformed cell surfaces has been studied through histochemical techniques using
lectins. Specific binding patterns to normal and transformed mammary tissues were evaluated by Isoform 1 fromCratylia mollis lectin (Cra Iso 1). Protocols using a direct method, incubation of Cra Iso I conjugated to peroxidase (Cra Iso 1-Per) with
mammary tissues, followed by diaminobenzidine and hydrogen peroxidase interaction, were performed. Neoplastic tissues, marked
by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison withCanavalia ensiformis lectin, Concanavalin A (Con A), conjugated to peroxidase (Con A-Per). The assay with Cra Iso 1 also indicated a possible
utilization of this lectin to characterize normal and transformed mammary cells. 相似文献
26.
Luana Bettanin Sumbal Saba Fábio Z. Galetto Gustavo A. Mike Jamal Rafique Antonio L. Braga 《Tetrahedron letters》2017,58(50):4713-4716
We describe herein a simple, fast and inexpensive protocol for the oxidative coupling of thiols employing a stoichiometric amount of DMSO and iodine as the catalyst. Various aromatic disulfides were obtained in good to excellent yields in short reaction times at room temperature, while aliphatic disulfides were achieved in good yields when the reactions were conducted under microwave irradiation. 相似文献
27.
In this work, a novel and simple analytical method using capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is proposed for the determination of the polyols erythritol, maltitol, xylitol, and sorbitol in sugar‐free chocolate. CE separation of the polyols was achieved in less than 6 min, and it was mediated by the interaction between the polyols and the borate ions in the background electrolyte, forming negatively charged borate esters. The extraction of the polyols from the samples was simply obtained using ultra‐pure water and ultrasonic energy. Linearity was assessed by calibration curves that showed R2 varying from 0.9920 to 0.9976. The LOQs were 12.4, 15.9, 9.0, and 9.0 μg/g for erythritol, maltitol, xylitol, and sorbitol, respectively. The accuracy of the method was evaluated by recovery tests, and the obtained recoveries varied from 70 to 116% with standard deviations ranging from 0.2 to 19%. The CE‐C4D method was successfully applied for the determination of the studied polyols in commercial samples of sugar‐free chocolate. 相似文献
28.
29.
Trubetskaya OE Shaloiko LA Demin DV Marchenkov VV Proskuryakov II Coelho C Trubetskoj OA 《Analytica chimica acta》2011,(2):263-268
Polyacrylamide gel electrophoresis of chernozem soil humic acids (HAs) followed by observation under UV (312 nm) excitation light reveals new low molecular weight (MW) fluorescent fractions. Ultrafiltration of HAs sample in 7 M urea on a membrane of low nominal MW retention (NMWR, 5 kDa) was repetitively used for separation of fluorescent and non-fluorescent species. Thirty ultrafiltrates and the final retentate R were obtained. Fluorescence maxima of separate ultrafiltrates were different and non-monotonously changed in the range of 475–505 nm. Fluorescence maxima of less than 490 nm were detected only in the four first utrafiltrates. For further physical–chemical analyses all utrafiltrates were combined into a fraction called UF < 5 (NMW < 5 kDa). Retentate R demonstrated very weak fluorescence under 270 nm excitation, while fluorescence intensity of UF < 5 was about six times higher than of the bulk HAs. Fraction UF < 5 was further ultrafiltrated on membranes of MNWR 3 kDa and 1 kDa, yielding three subfractions UF3-5, UF1-3 and UF < 1 with NMW 3–5 kDa, 1–3 kDa and <1 kDa, respectively. The validation of the UF procedure was performed by size exclusion chromatography on Sephadex G-25 column. The fluorescence maxima were found to be at 505, 488 and 465 nm for UF3-5, UF1-3 and UF < 1, respectively, with increasing of fluorescence intensity from UF3-5 to UF1-3 to UF < 1 fraction. EPR analysis showed that the amount of free radicals was the largest in retentate R and drastically decreased in fluorescent ultrafiltrates. The results demonstrate that more than one fluorophore is present in chernozem soil HAs complex. 相似文献
30.
Baki B. Sadi Chunsheng Li Gary H. Kramer Cassandra L. Johnson Queenie Ko Edward P. C. Lai 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(2):415-425
A new radioanalytical method was developed for rapid determination of 226Ra in drinking water samples. The method is based on extraction and preconcentration of 226Ra from a water sample to an organic solvent using a dispersive liquid-liquid microextraction (DLLME) technique followed by
radiometric measurement using liquid scintillation counting. In DLLME for 226Ra, a mixture of an organic extractant (toluene doped with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone) and a disperser
solvent (acetonitrile) is rapidly injected into the water sample resulting in the formation of an emulsion. Within the emulsion,
226Ra reacts with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone and partitions into the fine droplets of toluene. The water/toluene
phases were separated by addition of acetonitrile as a de-emulsifier solvent. The toluene phase containing 226Ra was then measured by liquid scintillation counting. Several parameters were studied to optimize the extraction efficiency
of 226Ra, including water immiscible organic solvent, disperser and de-emulsifier solvent type and their volume, chelating ligands
for 226Ra and their concentrations, inorganic salt additive and its concentration, and equilibrium pH. With the optimized DLLME conditions,
the accuracy (expressed as relative bias, B
r
) and method repeatability (expressed as relative precision, S
B
) were determined by spiking 226Ra at the maximum acceptable concentration level (0.5 Bq L−1) according to the Guidelines for Canadian Drinking Water Quality. Accuracy and repeatability were found to be less than −5%
(B
r
) and less than 6% (S
B
), respectively, for both tap water and bottled natural spring water samples. The minimum detectable activity and sample turnaround
time for determination of 226Ra was 33 mBq L−1 and less than 3 h, respectively. The DLLME technique is selective for extraction of 226Ra from its decay progenies. 相似文献