Léopold Thunus

Chemiluminescence as diagnostic tool. A review.

The principles of chemiluminescence and its applications as diagnostic tool are reviewed. After an introduction to the theoretical aspects of luminescence and energy transfer, the different classes of chemiluminogenic labels including luminol, acridinium compounds, coelenterazine and analogues, dioxetanes, systems based on peroxyoxalic acid and their derivatives are described emphasizing the molecules which best fulfil the requirements of todays clinical chemistry. Applications of chemiluminescence and enhanced chemiluminescence to immunoassays, receptor assays, DNA probes, biosensors and oxygen metabolism are discussed as well as the role of enzymes in the selectivity and the sensitivity of these reactions.

Application of Supercritical Carbon Dioxide for the Preparation of a Piroxicam-β-Cyclodextrin Inclusion Compound

AbstractPurpose. Piroxicam is a poorly soluble NSAID, whose solubility is enhanced when included into β-cyclodextrin. The preparation of a piroxicam-β-cyclodextrin inclusion compound using supercritical CO2 was investigated. Methods. The solubility and the stability of piroxicam in supercritical CO2 were determined. Then, the influence of the temperature, the pressure and the time of exposure on the inclusion rate was studied. Results. The solubility of piroxicam varied over a wide range depending on the temperature and pressure (from 0.006 to 1.500 mg/g of CO2). The temperature and the time of exposure had a great influence on the inclusion yield, while pressure did not and a complete inclusion was achieved by keeping a physical mixture of piroxicam and β-cyclodextrin (1:2.5 mol/mol) for 6 hours at 150°C and 15 MPa of CO2. This complex was characterized by Differential Scanning Calorimetry, differential solubility and Fourier Transform Infrared Spectrometry. Conclusions. Supercritical carbon dioxide may prove to be a novel useful complexation method of drugs into β-cyclodextrin.

Direct determination of tagitinin C in Tithonia diversifolia leaves by on-line coupling of supercritical carbon dioxide extraction to FT-IR spectroscopy by means of optical fibres

Supercritical fluid extraction (SFE) with carbon dioxide as extraction medium was on-line coupled to a FT-IR spectrometer equipped with a Mercury Cadmium Telluride (MCT) detector using a tailor-made high-pressure fibre optic flow cell. This method was optimised and developed for the monitoring in real time and the quantification of dynamic extractions of tagitinin C from Tithonia diversifolia leaves. In order to demonstrate the method ability to allow the direct quantification of tagitinin C in the extract medium the standard addition method was used. The area integration of curves obtained by plotting the absorbance of the highly specific C=O stretching vibration at 1668cm(-1) versus time (i.e. extractograms) was used as instrumental response. The SFE/FT-IR process was successfully validated using the accuracy profile as decision tool. On this basis, a linear regression model was chosen for the calibration curve. The relative standard deviation for repeatability and intermediate precision were between 0.8 and 3.1 %, respectively. Moreover, the method was found to be accurate as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the analytical range investigated (500-2500microg of added amount of tagitinin C). The proposed method allowed the non-destructive extraction of tagitinin C and its on-line quantitative determination in less than 25min thus facilitating the subsequent experiments or the pharmacological studies performed on this compound.

Spectres RMN-1H et -13C des acides mercapto-2 pyridinecarboxylique-5, mercapto-5 pyridinecarboxylique-2 et de leurs dérivés méthylés correspondants

Abstract Proton and carbon-13 chemical shifts and coupling constants of 2-mercapto-5-pyridine-carboxylic acid, 5-mercapto-2-pyridinecarboxylic acid and their seven respective methylated derivatives are reported. Substituent effects are discussed.

FT–IR measurement of tagitinin C after solvent extraction from Tithonia diversifolia

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was determined by FT-IR spectroscopy method. The crude ether extracts from aerial parts of the plant were evaporated to dryness and re-dissolved in tetrachloroethylene (C(2)Cl(4)) before analysis. The magnitude of the absorbance of the very specific CO stretching vibration (nu(CO)) at 1664.8cm(-1) was exploited in order to quantify tagitinin C. The determination coefficient (r(2)) of the calibration scale was 0.9994, the detection limit was lower than 3mugml(-1) and the quantification limit was lower than 10mugml(-1). Recovery values from 100.5 to 101.7% were found for spiked concentration levels from 19.91 to 89.95mugml(-1). The main characteristics of the curves obtained from the calibration standards and from the standard addition technique were not statistically different (Student t-test) suggesting that matrix effects were negligible. The results obtained for the determination of tagitinin C in the crude ether extract from aerial parts of T. diversifolia by LC and FT-IR spectroscopic method agreed well: 0.76+/-0.02 and 0.773+/-0.009, of tagitinin C in dried plant respectively.

Synthèse, étude théorique et évaluation biologique de dérivés du 4-amino-4H-1,2,4-triazole analogues des antibiotiques β-lactamiques

Abstract The synthesis of three classes of potential antibiotic compounds derived from 4-amino-4H-1,2,4-triazole and related to β-lactam antibiotics is described. Their originality belongs to the replacement of the β-lactam carbonyl moiety by another electrophilic centre of the same sp 2 geometry. As a result, their interaction with the bacterial target enzyme might lead to the formation of a covalent complex different from the classical acylenzyme. A theoretical study of their structural analogy and their reactivity compared to those of a model β-lactam justifies their interest in the present context. However, the actual biological results indicate a lack of antibacterial activity.

Determination of Zn, Cu, Ni and Co by Voltammetry in Plasma, without Mineralisation

Abstract Procedures are presented to determine successively Zn, Cu, Ni and Co in biological fluids by stripping voltammetry. Description of a desorption technique to separate proteins from metals is given and the efficiency is checked up on certified serum (seronormR). Comparison with wet mineralisation and oxygen burning is made. The program of differential pulse anodic stripping voltammetry (for Zn and Cu) and of adsorptive cathodic stripping voltammetry (for Ni and Co) is described.

Electrochemical Study Of 2-Mercaptopyridin-4-Caroxylic Acid and its Derivatives

Abstract The N-methylated derivatives of 2-mercapto-4-pyridincarboxylic acid have been studied by voltammetry as a function of polarographic parameters and pH. Their electrochemical behaviour has led us to propose a monoelectronic reduction of these compounds followed by a dimerization and a loss of sulfur compounds. The best conditions for the N-methylated derivatives determination by direct current and differential pulse polarography are also described.

Electrochemical Study of 2-Methylthiopyridin-4-carboxylic Acid, 2-Mercaptopyridin-4-carboxylic Acid and Their Methylesters

Abstract 2-methylthiopyridin-4-carboxylic acid, 2-mercapto-pyridin-4-carboxylic acid and their methyl esters have been studied by voltammetry as a function of polarogra-phic parameters and pH. These compounds have shown a polarographic behaviour essentially different as compared with the behaviour of the related N-methyl derivatives, while the latter are reduced in a one electron process followed by dimerization, the former give a two electron wave. Only the 2-mercaptopyridin-4-carboxylic acid and its methylester have shown a small dimerization wave followed by a strong competing wave. These compounds have also given anodic waves. Best conditions for quantitative determinations have been set up by direct current and differential pulse polarography.