Prediction of experimental parameters in combined isocratic and gradient elution reversed phase high performance liquid chromatography (RP-HPLC) using acetonitrile as organic modifier

The use of gradient elution in RP-HPLC is increasing. Aqueous buffers, such as phosphate at pH 1.7, with acetonitrile as the organic modifier are particularly advantageous as eluents with linear elution strength (LES). In the isocratic mode, under the experimental conditions used, fairly good linearity exists between logk' and x_B (x${}_{\text{B}}^{\text{º}}$ is the volume ratio of the organic modifier, i.e. acetonitrile) with a correlation coefficient of 0.9995. The relationship between isocratic and gradient elution parameters, such as x_B, x${}_{\text{B}}^{\text{º}}$ (starting composition in gradient elution), m (slope of the linear gradient), is transparent and the parameters of interest can be predicted fairly accurately using simple equations. The proposed system could be used in elaboration of a general retention index system for organic molecules in RP-HPLC.     

Studies on chemotherapeutics III. Synthesis and cyclisation of 5-substituted-4-oxo-1,4-dihydro-3-pyridinecarbonyl-semicarbazide and- thiosemicarbazide

1,4-Disubstituted-semicarbazide and thiosemicarbazide derivatives were synthetized from 5-substituted-4-oxo-1,4-dihydro-3-pyridinecarbohydrazides and cyclized to 3-mercapto-4H-1,2,4-triazoles. The obtained compounds could be S-methylated with methyl iodide in methanol. The new compounds were tested for antibacterial and antifungal activities.     

Computerized design of separation strategies by reversed-phase liquid chromatography: development of DryLab software

The development of DryLab software is a special achievement in analytical HPLC which took place in the last 16 years. This paper tries to collect some of the historical mile stones and concepts. DryLab, being always subject to change according to the needs of the user, never stopped being developed. Under the influence of an ever changing science market, the DryLab development team had to consider not just scientific improvements, but also new technological achievements, such as the introduction of Windows 1.0 and 3.1, and later Windows NT and 2000. The recent availability of new 32-bit programming tools allowed calculations of chromatograms to be completed more quickly so as to show peak movements which result for example from slight changes in eluent pH. DryLab is a great success of interdisciplinary and intercontinental cooperation by many scientists.     

A Universal Measure

It is shown that for any ring R of sets there is a locally convex Hausdorff topological vector space M(R) and a measure χ : R → M(R) such that for any other locally convex Hausdorff topological vector space W and any measure µ : R → W, there exists a unique continuous linear map µ : M(R) → W such that . Measure is defined in such a way that M(R)′, the space of all continuous linear functionals on M(R), corresponds to all finite, signed measures in the usual sense when R is a σ-ring. The problem of extending measures from R to the σ-ring generated by R is formulted in this setting. Properties of the universal measure χ are described. The topology of M(R) is studied via the pairing <M(R), M(R)′>. For example, the weak compact subsets of M(R)′ are characterized. This characterization gives rise to a simple proof of the Orlicz-Pettis theorem.     

Strategies for Improving Bioavailability,Bioactivity, and Physical-Chemical Behavior of Curcumin

Curcumin (CCM) is one of the most frequently explored plant compounds with various biological actions such as antibacterial, antiviral, antifungal, antineoplastic, and antioxidant/anti-inflammatory properties. The laboratory data and clinical trials have demonstrated that the bioavailability and bioactivity of curcumin are influenced by the feature of the curcumin molecular complex types. Curcumin has a high capacity to form molecular complexes with proteins (such as whey proteins, bovine serum albumin, β-lactoglobulin), carbohydrates, lipids, and natural compounds (e.g., resveratrol, piperine, quercetin). These complexes increase the bioactivity and bioavailability of curcumin. The current review provides these derivatization strategies for curcumin in terms of biological and physico-chemical aspects with a strong focus on different type of proteins, characterization methods, and thermodynamic features of protein–curcumin complexes, and with the aim of evaluating the best performances. The current literature review offers, taking into consideration various biological effects of the CCM, a whole approach for CCM-biomolecules interactions such as CCM-proteins, CCM-nanomaterials, and CCM-natural compounds regarding molecular strategies to improve the bioactivity as well as the bioavailability of curcumin in biological systems.     

Choline Chloride-Based Deep Eutectic Solvents as Green Effective Medium for Quaternization Reactions

The Menshutkin reaction represents the alkylation of tertiary amines by alkyl halide where the reactants are neutral and the products, quaternary ammonium salts, are two ions with opposite signs. The most commonly used organic solvents in quaternization reactions are volatile organic solvents (VOSs), namely acetone, anhydrous benzene, dry dichloromethane (DCM), dimethylformamide (DMF) and acetonitrile (ACN). The purpose of this work was to examine eutectic solvents as a “greener” alternative to conventional solvents so that quaternization reactions take place in accordance with the principles of green chemistry. Herein, sixteen eutectic solvents were used as replacements for volatile organic ones in quaternization reactions of isonicotinamide with substituted phenacyl bromides. The reactions were carried out at 80 °C by three synthetic approaches: conventional (4–6 h), microwave (20 min) and ultrasound (3 h). Microwave-assisted organic reactions produced the highest yields, where in several reactions, the yield was almost quantitative. The most suitable eutectic solvents were based on choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and glycerol, oxalic or levulinic acid as hydrogen bond donors (HBDs). The benefits of these three deep eutectic solvents (DESs) as a medium for quaternization reactions are the simplicity of their preparation for large-scale production, with inexpensive, available and nontoxic starting materials, as well as their biodegradability.