Effectively designed molecularly imprinted polymers for selective isolation of the antidiabetic drug metformin and its transformation product guanylurea from aqueous media

In the present study, two novel molecularly imprinted polymers (MIPs) with remarkable recognition properties for metformin and its transformation product, guanylurea, have been prepared for their selective, enrichment, isolation and removal from aqueous media. The prepared adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and swelling experiments. The performance of the prepared MIPs was evaluated by various parameters including the influence of pH, contact time, temperature and initial compound concentration. The effects on the adsorption behavior of the removal process parameters were studied and the equilibrium data were fitted by the Langmuir and Freundlich models. Due to the imprinting effect, adsorption performance of MIPs was always superior to its corresponding NIP (non-imprinted polymer), with maximum adsorption capacity ∼80 mg g⁻¹ for both MIPs. Stability and reusability of the MIPs up to the 5th cycle meant that they could be applied repeatedly without losing substantial removal ability. In the next step, the prepared MIP nanoparticles were evaluated as sorbents in a dispersive solid phase extraction (D-SPE) configuration for selective enrichment and determination of metformin and guanylurea in different aqueous matrices. Under the working extraction conditions, the D-SPE method showed good linearity in the range of 50–1000 ng L⁻¹, repeatability of the extractions (RSD 2.1–5.1%, n = 3), and low limits of detection (1.5–3.4 ng L⁻¹). The expanded uncertainty of the data obtained was estimated following a bottom-up approach. The proposed method combined the advantages of MIPs and D-SPE, and it could become an alternative tool for analyzing the residues of METF and its transformation product GUA in complex water matrices, such as wastewaters.     

Corrosion processes of iron in acidic solutions associated with potential oscillations induced by chlorates and perchlorates

Potential oscillations appear under current-controlled conditions of the chlorate- and perchlorate-perturbed electrochemical Fe|H₂SO₄ system. The potential oscillates between the active and passive states of Fe. It is shown that this oscillatory phenomenon is associated with localized corrosion of Fe due to the generation of chlorides via the reduction of chlorates and perchlorates by ferrous ions. Ferrous ions are generated either during the active dissolution of bare Fe (low-potential state) or during the passivation of Fe (high-potential state) due to a H⁺-catalyzed chemical dissolution of the oxide. Potential oscillations can be utilized to detect and characterize pitting corrosion of Fe in acidic solutions because, under current-controlled conditions, the halide-free Fe|H₂SO₄ system does not exhibit any kind of oscillatory phenomena. Characterization of pitting corrosion becomes possible through the analysis of galvanodynamic and galvanostatic curves obtained at various concentrations of chlorates and perchlorates. The variation of the anion concentration and applied current influence the onset and features of the potential oscillations.     

Comparison of the thermal behavior and conformational changes in partially and fully hydrated dipalmitoylphosphatidylcholine systems

The temperature dependence of conformational changes for partially and fully hydrated DPPC systems through two physicochemical techniques, namely DSC and Raman spectroscopy, is studied. DSC experiments have shown a different thermal behavior between the two considered systems, indicating the effective role of water in the thermal behavior. A temperature resolution of inter- and intramolecular interactions during the main melting phase transition was achieved by using three different Raman intensity ratios, which confirm that the main phase transition represents a two-stage transition. Van’t Hoff plots for the C–C, C–H, C=O and C₄N⁺ stretching modes, in a temperature range just below the main transition temperature, have been used to compare the thermodynamic parameters extracted by the two physicochemical techniques. The significance of these results can be summarized as follows: (a) DSC and Raman spectroscopy have shown complementary results indicating that DPPC exists in partially or fully hydrated states; (b) thermodynamic parameters ΔΗ and ΔS calculated in both techniques for the two different hydration states of DPPC were in harmony; (c) water more significantly affects the thermal and dynamic properties of fully hydrated DPPC bilayers than of the partially hydrated DPPC; and (d) water disturbs the head-group packing, the alkyl chains interactions and the mesophase region. It appears that the amount of water plays a vital role in the bilayer structure. As more and more extensive studies appear in the literature on biomolecules or drug membrane interactions, this information will be valuable in understanding the role of water in these interactions.     

Condensation Reaction of Dimethyltin(IV) Oxide with 2‐(2,3‐Dichloroanilino)benzoic Acid Synthesis and Study of a Novel Dimeric Tetraorganodistannoxane

The novel symmetric dimeric tetraorganodistannoxane [(Me₂Sn)₄(DCPA)₂)O₂(OH)₂] ( 2 ) and [(Me₂Sn)₄(DCPA)₂)O₂(OC₂H₅)₂] ( 3 ) where HDCPA is 2‐(2,3‐dichloroanilino)benzoic acid ( 1 ) have been prepared. The crystal structure of 3 has been determined by X‐ray crystallography. Three distannoxane rings are present to the centrosymmetric dimeric tetraorganodistannoxane by virtue of μ₃‐oxo form the central R₄Sn₂O₂ core with a planar Sn₂O₂ ring, resulting in a ladder type structural motif. Five‐coordinated tin atoms are present in the distannoxane dimer. The ligands act as monodentate agents, thus rendering the tin atom five‐coordinated. Significant π → π stacking interactions and intramolecular hydrogen bonds stabilize the structure 3 . The polar imino hydrogen atom participates in intramolecular hydrogen bonds. The formation of the dimeric distannoxanes 2 and 3 represent a ladder‐type carboxylates in which the insertion of a μ₂‐OH or a μ₂‐OC₂H₅ group occurs. This unusual result can be interpreted in terms of a competition between the strength different donors, in which the –OH or the –OC₂H₅ groups show higher donor capacity than the carboxylato group of DCPA.     

Thermosensitive noncovalently bonded block copolymerlike micelles from interpolymer complexes

Interpolymer complexes between polystyrene‐b‐poly(2‐vinylpyridine), (PS‐P2VP), and poly(methacrylic acid) (PMAA), have been studied in dioxane. Dioxane is a good solvent for PS‐P2VP copolymers but it is a nonsolvent for PMAA at room temperature. In this way noncovalent bonded micelles are formed after mixing the solutions of the polymers at 60 °C and then allowing them to cool at room temperature. Static and dynamic light scattering as well as viscosity measurements have been used to study the dependence of aggregate mass and size as a function of the molar ratio of functional groups in PS‐P2VP/PMAA mixtures, as well as temperature. Plots of apparent average molecular weight and hydrodynamic radius of the aggregates versus amine to carboxyl group ratio show a maximum at a ratio close to one. The size of the aggregates decreases at higher ratios because of the formation of more stable micelles with smaller cores. In all cases rather compact structures were formed, as evidenced by viscometry. The mass of the aggregates was found to decrease by an increase in temperature while hydrodynamic radii were increased. This was attributed to the increase of the thermodynamic quality of the solvent toward PMAA as temperature increases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6230–6237, 2004     

A Family of Potent Ru(II) Photosensitizers with Enhanced DNA Intercalation: Bimodal Photokillers

A new family of Ru(II)‐based photosensitizers was synthesized and systematically characterized. The ligands employed to coordinate the ruthenium metal center were the commercially available 2,2′‐bipyridine and a pyridine‐quinoline hybrid bearing an anthracene moiety. The complexes obtained carry either or Cl^? counterions. These counterions determine the complexes' hydrophobic or hydrophilic character, respectively, therefore dictating their solubility in biologically related media. All photosensitizers exhibit characteristic, relatively strong and wide UV–Vis absorption spectral profiles. Their high efficiency in generating cytotoxic singlet oxygen was established (up to Φ_Δ ~0.8). Moreover, the interaction of these photosensitizers with double‐stranded DNA was studied fluoro‐ and photospectroscopically and their binding affinities were found to be of the order of 3 × 10⁷ M^?1. All complexes are photocytotoxic to DU145 human prostate cancer cells. The highest light‐induced toxicity was conferred by the photosensitizers bearing Cl^? counterions, probably due to the looser ionic “chaperoning” of Cl^?, in comparison to , leading to higher cell internalization.     

Synthesis of PhTAD-substituted dihydropyrrole derivatives via stereospecific C–H amination

Research on Chemical Intermediates - Stereospecific α-amination has been accomplished via addition of N-phenyltriazolinedione (PhTAD) to the allylic position of dihydropyrroles. The aim of...     

Pyrazoles and Pyrazolines as Anti-Inflammatory Agents

The five-membered heterocyclic group of pyrazoles/pyrazolines plays important role in drug discovery. Pyrazoles and pyrazolines present a wide range of biological activities. The synthesis of the pyrazolines and pyrazole derivatives was accomplished via the condensation of the appropriate substituted aldehydes and acetophenones, suitable chalcones and hydrazine hydrate in absolute ethanol in the presence of drops of glacial acetic acid. The compounds are obtained in good yields 68–99% and their structure was confirmed using IR, ¹H-NMR, ¹³C-NMR and elemental analysis. The novel derivatives were studied in vitro for their antioxidant, anti-lipid peroxidation (AAPH) activities and inhibitory activity of lipoxygenase. Both classes strongly inhibit lipid peroxidation. Compound 2g was the most potent lipoxygenase inhibitor (IC₅₀ = 80 µM). The inhibition of the carrageenin-induced paw edema (CPE) and nociception was also determined, with compounds 2d and 2e being the most potent. Compound 2e inhibited nociception higher than 2d. Pyrazoline 2d was found to be active in a preliminary test, for the investigation of anti-adjuvant-induced disease (AID) activity. Pyrazoline derivatives were found to be more potent than pyrazoles. Docking studies of the most potent LOX inhibitor 2g highlight hydrophobic interactions with VAL126, PHE143, VAL520 and LYS526 and a halogen bond between the chlorine atom and ARG182.     

Organotin adducts with pyrimidinethione: crystal structure of dimethyldi(pyrimidine‐2‐thiolato)tin(IV) and diphenyldi(pyrimidine‐2‐thiolato)tin(IV)

The complexes dimethyldi(pyrimidine‐2‐thiolato)tin(IV) ( 1 ) and diphenyldi(pyrimidine‐2‐thiolato)tin(IV) ( 2 ) have been structurally ­characterized by means of X‐ray crystallography. Complex 1 exhibits strong π–π stacking interactions and adduct 2 is self‐assembled via intermolecular hydrogen bonds, C H–π and π–π stacking interactions. Partial solvolysis occurs in organic solvents for 1 and 2 . Copyright © 2000 John Wiley & Sons, Ltd.     

Comparison of distillation and ultrasound-assisted extraction methods for the isolation of sensitive aroma compounds from garlic (Allium sativum)

A comparative study of traditional simultaneous distillation extraction (SDE), microwave assisted hydrodistillation extraction (MWHD) and ultrasound-assisted extraction (USE) is presented, for the extraction of essential oils from fresh garlic (Allium sativum) cloves. Each method is evaluated in terms of qualitative and quantitative composition of the isolated essential oil. The highly reactive sulfur molecules of the garlic volatile fraction show variable response to the different isolation methods. The application of ultrasound for the extraction of the essential oil is considered to cause a lesser damage of thermal-sensitive molecules, thus, providing a better approach of the compounds primarily responsible for the characteristic odor and taste of freshly chopped garlic. All heat-involving isolation procedures have been shown to differentiate the volatile-fraction profile as analyzed by GC-MS. Especially when grouping the compounds into cyclic and acyclic, the percentage concentrations drop from 77.4% to 8.7% for the acyclic while that of the cyclic compounds increase from 4.7% to 70.8%. The observed fact may be attributed to the effect of the heat applied, which changes from harsh thermal treatment (SDE) to short time thermal (MWHD) and room-temperature isolation (USE). The use of USE proves to be crucial in order to provide reliable insight into garlic's chemistry.