Evaluation of Electrochromic Properties of Polypyrrole/Poly(methylene blue) Layer Doped by Polysaccharides

Polypyrrole (Ppy) and poly(methylene blue) (PMB) heterostructure (Ppy-PMB) was electrochemically formed on the indium tin oxide (ITO) coated glass slides, which served as working electrodes. For electropolymerization, a solution containing pyrrole, methylene blue, and a saccharide (lactose, sucrose, or heparin) that served as dopant was used. The aim of this study was to compare the effect of the saccharides (lactose, sucrose, and heparin) on the electrochromic properties of the Ppy-PMB layer. AFM and SEM have been used for the analysis of the surface dominant features of the Ppy-PMB layers. From these images, it was concluded that the saccharides used in this study have a moderate effect on the surface morphology. Electrochromic properties were analyzed with respect to the changes of absorbance of the layer at two wavelengths (668 nm and 750 nm) by changing the pH of the surrounding solution and the potential between +0.8 V and −0.8 V. It was demonstrated that the highest absorbance changes are characteristic for all layers in the acidic media. Meanwhile, the absorbance changes of the layers were decreased in the more alkaline media. It was determined that the Ppy-PMB layers with heparin as a dopant were more mechanically stable in comparison to the layers doped with lactose and sucrose. Therefore, the Ppy-PMB layer doped with heparin was selected for the further experiment and it was applied in the design of electrochromic sensors for the determination of three xanthine derivatives: caffeine, theobromine, and theophylline. A linear relationship of ΔA (∆A = A+0.8V – A−0.8V) vs. concentration was determined for all three xanthine derivatives studied. The largest change in optical absorption was observed in the case of theophylline determination.

Xanthine: Synthetic Strategy And Biological Activity

Xanthine and its derivatives belong to the class of purine alkaloids. They are natural bases holding nitrogen atoms within the molecular structure, and they have an effective pharmacological alteration in both animals and human beings. Substituted xanthine, theophylline/caffeine being prototype, is one of the derivatives which have shown prominent binding to adenosine receptors as agonist or antagonist. Various mechanistic approaches are involved in exerting bronchospasmolytic, neuroprotective, hypoglycemic, MAO modulatory, along cardiac effects. Mostly, xanthine derivatives reduce inflammation and bronchospasm in asthmatic conditions. Other therapeutics effects are in the management of cancer, Alzheimer's disease, vasoconstriction, and also possess excellent central nervous system-penetration ability; thus, they can also be used as stimulants and anti-depressants. Their actions are relatively very weak, but their pharmacological effects are also associated with snarl-up adenosine-mediated functions. An assortment of the biological profile of the xanthine scaffold attracted many research groups over the years to explore this nucleus vividly. The present review is aimed to cover every aspect of the xanthine moiety reported in the earlier years. This review covers all the major biological roles and various synthetic strategies adopted to synthesize xanthine moiety and its derivatives.

Facile N9-Alkylation of Xanthine Derivatives and Their Use as Precursors for N-Heterocyclic Carbene Complexes

The xanthine-derivatives 1,3,7-trimethylxanthine, 1,3-dimethyl-7-benzylxanthine and 1,3-dimethyl-7-(4-chlorobenzyl)xanthine are readily ethylated at N9 using the cheap alkylating agents ethyl tosylate or diethyl sulfate. The resulting xanthinium tosylate or ethyl sulfate salts can be converted into the corresponding PF6- and chloride salts. The reaction of these xanthinium salts with silver(I) oxide results in the formation of different silver(I) carbene-complexes. In the presence of ammonia, ammine complexes [Ag(NHC)(NH3)]PF6 are formed, whilst with Et2NH, the bis(carbene) salts [Ag(NHC)2]PF6 were isolated. Using the xanthinium chloride salts neutral silver(I) carbenes [Ag(NHC)Cl] were prepared. These silver complexes were used in a variety of transmetallation reactions to give the corresponding gold(I), ruthenium(II) as well as rhodium(I) and rhodium(III) complexes. The compounds were characterized by various spectroscopic methods as well as X-ray diffraction.

Study on the influence of 7-β-hydroxy-γ-aryloxypropylxanthinyl-8-thioalkanic acid derivatives on the lipid metabolism in experiment

Statin side effects are not a rare occurrence, in particular dyspeptic disorders, insomnia, headache, skin erythema, rash are often noted. All of this determines scientists to find new effective and low-toxic hypolipidemic agents. Various natural and synthetic xanthine derivatives have been recognized as therapeutically potential compounds and reported to control various diseases. Therefore, the study of new xanthine derivatives and their hypolipidemic effects, which would have a significant therapeutic effect with minimal side effects, is relevant. The aim of the study was to examine the effect of 7-β-hydroxy-γ-aryloxypropylxanthinyl-8-thioalkanic acid derivatives on lipidogram parameters in experimental laboratory rats. Materials and methods. The objects of the study were 7-β-hydroxy-γ-aryloxypropylxanthinyl-8-thioalkanic acid derivatives. The experiments were performed in white laboratory Wistar rats weighing 180–220 g. Experimental modeling of hyperlipidemia – tween model: intraperitoneal administration of tween-80 at a dose of 200 mg/100 g body weight. The test compounds were administered orally, simultaneously with tween, at a dose of 1/10 of LD50 (previously calculated by Prozorovsky express method) for 6 days. The following indicators of lipidogram were determined: total cholesterol (TC), high-density lipoprotein cholesterol (HDL cholesterol), low-density lipoprotein cholesterol (LDL cholesterol), triglycerides (TG) and atherogenic index of plasma: TC – HDL cholesterol / HDL cholesterol. The experiments were carried out with respect to Bioethical rules and norms. Results. The studies have shown data on the hypolipidemic activity of 7-β-hydroxy-γ-aryloxypropylxanthinyl-8-thioalkane acid derivatives. According to the conditional efficiency index Ʃ, which included the overall percentage of the following indicators – total cholesterol, low-density lipoprotein cholesterol and triglycerides, the leading compounds were 2439 (87.47 %), 6047 (82.30 %). The reference drug atorvastatin had a value of 82.98 %. Conclusions. The major compound was 2439 identified among all compared to the control group. The prospect of further research is a more detailed study on the ability of xanthine derivatives to exhibit hypolipidemic effects and to influence oxidative stress in various hyperlipidemic models.

SYNTHESIS, CYTOTOXIC AND ANTIOXIDANT ACTIVITY OF NEW 1,3-DIMETHYL-8-(CHROMON-3-YL)-XANTHINE DERIVATIVES CONTAINING 2,6-DI-TERT-BUTYLPHENOL FRAGMENT

The condensation of 3-formylchromones and 6-amino-5-((3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)amino)-1,3-dimethyl-pyrimidine-2,4(1H,3H)-dione allowed us to synthesize chromone based hybrids containing additional pharmacophores - xanthine and sterically hindered phenol fragments. Novel compounds have been characterized by 1H...

Bronchospasmolytic and Adenosine Binding Activity of 8- (Proline / Pyrazole)-Substituted Xanthine Derivatives

Background: ABSTRACT: Background: 8-Phenyltheophylline derivatives exhibit prophylactic effects at a specific dose but do not produce the cardiovascular or emetic side effects associated with xanthines, thereby exhibiting unique characteristics of potential therapeutic importance. Methods: Novel series of 8-(proline/pyrazole)-substituted xanthine analogs has been synthesized. The affinity and selectivity of compounds to adenosine receptors have been assessed by radioligand binding studies. The synthesized compounds also showed good bronchospasmolytic properties (increased onset of bronchospasm; decreased duration of jerks) with 100% survival of animals in comparison to the standard drug. Besides, compound 8f & 9f showed good binding affinity in comparison to other synthesized compounds in the micromolar range. Results: The maximum binding affinity of these compounds was observed for A2B receptors, which is ~ 7 or 10 times higher as compared to A1, A2A and A3 receptors. The newly synthesized derivatives 8f, 9a-f, 17g-m, and 18g-m displayed significant protection against histamine aerosol induced bronchospasm in guinea pigs. Conclusion: Newly synthesized proline/pyrazole based xanthines compounds showed a satisfactory binding affinity for adenosine receptor subtypes. Replacement or variation of substituted proline ring with substituted pyrazole scaffold at 8thposition of xanthine moiety resulted in the reduction of adenosine binding affinity and bronchospasmolytic effects.