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1.
Front Chem ; 12: 1393860, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38752198

RESUMO

Long-term electrolyses of glucose in a potassium carbonate (K2CO3) aqueous electrolyte have been performed on graphite felt electrodes with TEMPO as a homogeneous catalyst. The influences of the operating conditions (initial concentrations of glucose, TEMPO, and K2CO3 along with applied anode potential) on the conversion, selectivity toward gluconate/glucarate, and faradaic efficiency were assessed first. Then, optimizations of the conversion, selectivity, and faradaic efficiency were performed using design of experiments based on the L9 (34) Taguchi table, which resulted in 84% selectivity toward gluconate with 71% faradaic efficiency for up to 79% glucose conversion. Side products such as glucaric acid were also obtained when the applied potential exceeded 1.5 V vs. reversible hydrogen electrode.

2.
Anal Bioanal Chem ; 415(22): 5337-5352, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37394521

RESUMO

Analyzing the composition of (human) urine plays a major role in the fields of biology and medicine. Organic molecules (such as urea, creatine) and ions (such as chloride, sulfate) are the major compounds present in urine, the quantification of which allows for the diagnosis of a subject's health condition. Various analytical methods have been reported for studying urine components and validated on the basis of known and referenced compounds. The present work introduces a new method able to simultaneously determine both major organic molecules and ions contained in urine, by combining ion chromatography using a conductimetric detector with mass spectroscopy. The analysis of organic and ionized compounds (anionic and cationic) was achieved in double injections. For quantification, the standard addition method was used. Human urine samples were pre-treated (diluted and filtered) for IC-CD/MS analysis. The analytes were separated in 35 min. Calibration ranges (0-20 mg.L-1) and correlation coefficients (> 99.3%) as well as detection (LODs < 0.75 mg.L-1) and quantification (LOQs < 2.59 mg.L-1) limits were obtained for the main organic molecules (lactic, hippuric, citric, uric, oxalic acids, urea, creatine, and creatinine) and ions (chloride, sulfate, phosphate, sodium, ammonium, potassium, calcium, and magnesium) contained in urine. The intra- and inter-day accuracies of the analytes consistently ranged from 0.1 to 5.0%, and the precision was within 4.0%. For all analytes, no significant matrix effects were observed, and recoveries ranged from 94.9 to 102.6%. Finally, quantitative results of analytes were obtained from 10 different human urine samples.


Assuntos
Cloretos , Creatina , Humanos , Espectrometria de Massas , Cromatografia , Compostos Orgânicos , Sulfatos , Ureia , Cromatografia Líquida de Alta Pressão/métodos
3.
Mar Drugs ; 20(2)2022 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-35200622

RESUMO

The organization of bacteria in biofilms is one of the adaptive resistance mechanisms providing increased protection against conventional treatments. Thus, the search for new antibiofilm agents for medical purposes, especially of natural origin, is currently the object of much attention. The objective of the study presented here was to explore the potential of extracts derived from three seaweeds: the green Ulva lactuca, the brown Stypocaulon scoparium, and the red Pterocladiella capillacea, in terms of their antibiofilm activity against P. aeruginosa. After preparation of extracts by successive maceration in various solvents, their antibiofilm activity was evaluated on biofilm formation and on mature biofilms. Their inhibition and eradication abilities were determined using two complementary methods: crystal violet staining and quantification of adherent bacteria. The effect of active extracts on biofilm morphology was also investigated by epifluorescence microscopy. Results revealed a promising antibiofilm activity of two extracts (cyclohexane and ethyl acetate) derived from the green alga by exhibiting a distinct mechanism of action, which was supported by microscopic analyses. The ethyl acetate extract was further explored for its interaction with tobramycin and colistin. Interestingly, this extract showed a promising synergistic effect with tobramycin. First analyses of the chemical composition of extracts by GC-MS allowed for the identification of several molecules. Their implication in the interesting antibiofilm activity is discussed. These findings suggest the ability of the green alga U. lactuca to offer a promising source of bioactive candidates that could have both a preventive and a curative effect in the treatment of biofilms.


Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Pseudomonas aeruginosa/efeitos dos fármacos , Antibacterianos/isolamento & purificação , Colistina/farmacologia , Sinergismo Farmacológico , Cromatografia Gasosa-Espectrometria de Massas , Phaeophyceae/metabolismo , Rodófitas/metabolismo , Solventes/química , Tobramicina/farmacologia , Ulva/metabolismo
4.
Mater Sci Eng C Mater Biol Appl ; 33(1): 64-6, 2013 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25428043

RESUMO

Effect of copper ions on the electrochemical behaviour of an alkylaminethiol monolayer has been studied by electrochemical impedance spectrosocpy. RAMAN experiment shows the effective adsorption of receptor onto the gold surfaces. The study of Nyquist plot shows that the gold/monolayer/electrolyte interface can be described by a serial combination of two R, CPE electrical circuits. In the presence of increasing amounts of copper, the Nyquist plots at low frequencies were modified showing an increase of the resistance of the second R, CPE electrical circuit. Moreover, this increase of resistance varies linearly with the amounts of copper ions added in solution from 10(-8) mol·L(-1) to 10(-5) mol·L(-1).


Assuntos
Cobre/química , Cisteamina/química , Eletroquímica/métodos , Simulação por Computador , Impedância Elétrica , Eletrodos , Ouro , Íons , Análise Espectral Raman
5.
J Photochem Photobiol B ; 110: 34-42, 2012 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-22436506

RESUMO

Alkali-labile lesion to DNA photosensitized, via an electron transfer mechanism, by three non-steroidal anti-inflammatory drugs (NSAIDs), ketoprofen, tiaprofenic acid and naproxen and their photoproducts during drug photolysis, was investigated using (32)P-end labelled synthetic oligonucleotide. These photooxidative damages were correlated with the photophysical and electrochemical properties of drugs, appearing as the photosensitizer PS. Photophysical studies provided the excited state energies of the photosensitizer while their redox potentials and the relative stabilities of the PS(-) radical-anions were determined by cyclic voltammetry. On the basis of these data, we have calculated the Gibbs energy of photoinduced electron-transfer and evaluated the exergonicity of the oxidative photodamage. Moreover, kinetic control may be invoked according to the stabilities of PS(-). Applied to this NSAIDs family, the photoxidative damages through electron transfer mechanism were analyzed and a good correlation with photoredox and photobiological properties was established.


Assuntos
Anti-Inflamatórios não Esteroides/química , DNA/química , Cetoprofeno/química , Naproxeno/química , Fotólise , Fármacos Fotossensibilizantes/química , Propionatos/química
6.
Org Biomol Chem ; 2(6): 876-83, 2004 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-15007417

RESUMO

Synthetic pathways to a range of novel semi-rigid tetradentate ligands, with sulfur, amido or amino donor groups, designed to coordinate technetium 99m have been developed. The technetium-99m complexes have been prepared and their stabilities in serum and by metathesis reaction via cysteine exchange reactions were compared. HPLC comparison of two (99m)Tc-complexes and their rhenium analogues led to the first proof of the nature of our radioactive complexes.

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