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31.
da Rocha DR de Souza AC Resende JA Santos WC dos Santos EA Pessoa C de Moraes MO Costa-Lotufo LV Montenegro RC Ferreira VF 《Organic & biomolecular chemistry》2011,9(11):4315-4322
A synthetic method to obtain α- and β-pyran naphthoquinones 10 and 11 with a hydroxyl substituent on the aromatic ring was developed. Two series of α- and β-pyran naphthoquinones were obtained from the 8-hydroxy-lawsone, and their anticancer properties were evaluated against four tumor cell lines. In general, the new compounds displayed good activity, possibly indicating that these compounds have increased pro-oxidant capacity. The 9-hydroxy-α-lapachone and 7-hydroxy-β-lapachone analogues of the natural products α-lapachone and β-lapachone were successfully produced by this methodology. 相似文献
32.
Influence of Inert and Oxidizing Atmospheres on the Physical and Optical Properties of Luminescent Carbon Dots Prepared through Pyrolysis of a Model Molecule
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Cláudia Emanuele Machado Letícia Gazola Tartuci Prof. Dr. Honória de Fátima Gorgulho Prof. Dr. Luiz Fernando Cappa de Oliveira Jefferson Bettini Prof. Dr. Daniela Pereira dos Santos Prof. Dr. Jefferson Luis Ferrari Prof. Dr. Marco Antônio Schiavon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4556-4563
This work used l ‐tartaric acid as a model molecule to evaluate how the use of inert and oxidizing atmospheres during pyrolysis affected the physical and optical properties of the resulting carbon dots (CDs). Pyrolysis revealed to be a simple procedure that afforded CDs in a single step, dismissed the addition of organic solvents, and involved only one extraction stage that employed water. By X‐ray diffraction a dependency between the structure of the CDs and the atmosphere (oxidizing or inert) used during the pyrolysis was found. Potentiometric titration demonstrated that the CDs were largely soluble in water; it also aided characterization of the various groups that contained sp3‐hybridized carbon atoms on the surface of the dots. Raman spectroscopy suggested that different amounts of sp2‐ and sp3‐hybridized carbon atoms emerged on the CDs depending on the pyrolysis atmosphere. In conclusion, the pyrolysis atmosphere influenced the physical properties, such as the composition and the final structure. 相似文献
33.
Thereza Christina Vessoni Penna Angela Faustino Jozala Letícia Célia De Lencastre Novaes Adalberto Pessoa Jr. Olivia Cholewa 《Applied biochemistry and biotechnology》2005,122(1-3):619-637
Nisin is a bacteriocin that inhibits the germination and growth of Gram-positive bacteria. With nisin expression related to growth conditions of Lactococcus lactis subsp. lactis, the effects of growth parameters, media components, and incubation time were studied to optimize expression. L. lactis ATCC 11454 was grown (100 rpm at 30°C for 36 h) in both M17 and MRS standard broth media (pH 6.0–7.0) supplemented with sucrose (1.0–12.5 g/L), potassium phosphate (0.13 g/L), asparagine (0.5 g/L), and sucrose (0.24 g/L), and diluted 1:1 with liquid nonfat milk. Liquid nonfat milk, undiluted, was also used as another medium (9% total solids, pH 6.5). Nisin production was assayed by agar diffusion using Lactobacillus sake ATCC 15521 (30°C for 24 h) as the sensitive test organism. The titers of nisin expressed and released in culture media were quantified and expressed in arbitrary units (AU/L of medium) and converted into known concentrations of “standard nisin” (Nisaplin®, g/L). The detection of nisin activity was <0.01 AU/L in M17 and MRS broths, and 7.5 AU/L in M17 with 0.14% sucrose or 0.13% other supplements, and the activity increased to 142.5 AU/L in M17 diluted with liquid nonfat milk (1:1). The 25% milk added to either 25% M17 or 25% MRS provided the highest levels of nisin assayed. 相似文献
34.
Laís E. Scheeren Daniele R. Nogueira-Librelotto Joana R. Fernandes Letícia B. Macedo Ana Isa P. Marcolino M. Pilar Vinardell 《Analytical letters》2018,51(10):1445-1463
Analytical methods by reversed-phase high-performance liquid chromatography (HPLC) and ultraviolet–visible spectrophotometry were developed and validated to determine doxorubicin in pH-sensitive chitosan nanoparticles. Chromatographic separation was performed on a reversed-phase C18 column, with ultraviolet detection at 254?nm and a mobile phase composed by 90% (v/v) acetonitrile in water and water pH 3.0 (33:67, v/v). The spectrophotometry method had the wavelength set at 480?nm and pH 3.0 water was used as a diluent. Calibration curves were linear from 1 to 30?µg/?mL (r?>?0.9995) and the specificity was demonstrated by verifying the absence of interferences from nanoparticle components. The values of accuracy and precision were within the acceptable limits, and robustness studies were performed by a two-level full factorial design. The validated methods were further tested to assess doxorubicin content in six different batches of pH-sensitive chitosan nanoparticles. The comparative analyses showed nonsignificant differences (p?>?0.05). Likewise, the HPLC method was successfully applied to determine the drug encapsulation efficiency as well as to measure doxorubicin during in vitro release assays and degradation kinetic studies under ultraviolet light C irradiation. Both methods fulfilled all validation parameters and were shown to be suitable for the characterization of doxorubicin-loaded pH-sensitive chitosan nanoparticles, without interferences from nanoparticle matrix. 相似文献
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37.
Felipe S. Vilhena Letícia R. Teixeira Odivaldo Cambraia Alves Heloisa Beraldo Fabio da S. Miranda Judith Felcman 《Journal of solution chemistry》2013,42(3):555-565
The binary systems of iron(II) and iron(III) with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives were studied in aqueous solution by pH-potentiometry, ultraviolet–visible spectroscopy and EPR spectra. The formation constants of the iron(II) and iron(III) complexes were calculated from potentiometric and electronic absorption data at 25 °C and ionic strength μ = 0.1 mol·L?1 using the HYPERQUAD program. The values of the formation constant of the FeL species decrease in the order Fe:H2Am4DH > Fe:H2Am4Me ≈ Fe:H2Am4Et > Fe:H2Am4Ph in the same way as the basicity of the ligands. The species distribution diagrams show that the species FeL2 predominates at physiological pH in the Fe:H2Am4DH, Fe:H2Am4Me and Fe:H2Am4Et systems. The similar EPR spectra of these iron(III) binary systems indicate the same coordination spheres around the metallic center and the EPR g values suggests that the unpaired electron is in the dxy orbital, indicating a d xz 2 d yz 2 d xy 1 ground state configuration for the complexes. For the Fe(III):H2Am4Ph system the EPR results indicated dimerization and antiferromagnetic interaction due to the presence of only one thiosemicarbazone ligand around the metallic center. 相似文献
38.
Letícia Caramori Cefali Ilza Maria de Oliveria Sousa Mariana Cecchetto Figueiredo Ana Lucia Tasca Gois Ruiz Mary Ann Foglio 《Natural product research》2020,34(18):2677-2682
AbstractA flavonoid enriched extract (FE) was obtained from grape peels, and in vitro SPF, antioxidant activity, and effects on cell viability of this extract were tested with the intent to develop a cosmetic product. A formulation was developed with the FE, and the stability of this mixture was evaluated in terms of pH, density, viscosity, and SPF (90-days). FE showed no cytotoxicity to human keratinocytes and an in vitro SPF of 18.56 (UV-spectrophotometry). Further, FE showed a UVA protection factor of 3.17?±?0.2, a critical wavelength of 318.0?±?0.1 and a UVA/UVB of 0.9. Antioxidant activity assays resulted in 92.08% and 86.85% of activity against DPPH and ABTS (IC50 = 296.90?±?1.2?µg/mL and 643.13?±?0.9?µg/mL), respectively. Finally, SPF of formulation with FE was 12.45. Results from the in vitro SPF and product stability tests (especially storage under refrigeration), indicate that FE is a promising compound for use as an innovative sunscreen formulation. 相似文献
39.
Arunabha Sen Subhajit Dutta Gourab K. Dam Dr. Partha Samanta Sumanta Let Dr. Shivani Sharma Dr. Mandar M. Shirolkar Prof. Sujit K. Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(53):13442-13449
Fabricating new and efficient materials aimed at containment of water contamination, in particular removing toxic heavy metal based oxo-anions (e. g. CrO42−, TcO4−) holds paramount importance. In this work, we report two new highly stable imidazolium based ionic porous organic polymers (iPOPs) decorated with multiple interaction sites along with electrostatics driven adsorptive removal of such oxo-anions from water. Both the iPOPs (namely, iPOP-3 and iPOP-4) exhibited rapid sieving kinetics and very high saturation uptake capacity for CrO42− anions (170 and 141 mg g−1 for iPOP-3 and iPOP-4 respectively) and ReO4− (515.5 and 350.3 mg g−1 for iPOP-3 and iPOP-4 respectively), where ReO4− anions being the non-radioactive surrogative counterpart of radioactive TcO4− ions. Noticeably, both iPOPs showed exceptional selectivity towards CrO42− and ReO4− even in presence of several other concurrent anions such as Br−, Cl−, SO42−, NO3− etc. The theoretical binding energy calculations via DFT method further confirmed the preferential interaction sites as well as binding energies of both iPOPs towards CrO42− and ReO4− over all other competing anions which corroborates with the experimental high capacity and selectivity of iPOPs toward such oxo-anions. 相似文献
40.
Letícia Coli Louvisse de Abreu Bárbara de Azevedo Abrahim-Vieira Alessandra Mendonça Teles de Souza Eduardo Costa Pinto Mariana da Silva Gonçalves Alice Simon Gil Mendes Viana Carlos Rangel Rodrigues Valeria Pereira de Sousa Lucio Mendes Cabral 《Biomedical chromatography : BMC》2020,34(7):e4832
Injectable solutions containing epinephrine (EPI) and norepinephrine (NE) are not stable, and their degradation is favored mainly by the oxidation of catechol moiety. As studies of these drugs under forced degradation conditions are scarce, herein, we report the identification of their degradation products (DP) in anesthetic formulations by the development of stability-indicating HPLC method. Finally, the risk assessment of the major degradation products was evaluated using in silico toxicity approach. HPLC method was developed to obtain a higher selectivity allowing adequate elution for both drugs and their DPs. The optimized conditions were developed using a C18 HPLC column, sodium 1-octanesulfonate, and methanol (80:20, v/v) as mobile phase, with a flow rate of 1.5 mL/min, UV detection at 199 nm. The analysis of standard solutions with these modifications resulted in greater retention time for EPI and NE, which allow the separation of these drugs from their respective DPs. Then, five DPs were identified and analyzed by in silico studies. Most of the DPs showed important alerts as hepatotoxicity and mutagenicity. To the best of our acknowledgment, this is the first report of a stability-indicating HPLC method that can be used with formulations containing catecholamines. 相似文献