Reaction of Amino-Terminated PAMAM Dendrimers with Carbon Dioxide in Aqueous and Methanol Solutions

Polyamines have been used as active materials to capture carbon dioxide gas based on its well-known reaction with amines to form carbamates. This work investigates the reactions between three amino-terminated poly(amidoamine) (PAMAM) dendrimers (G1, G3 and G5) and CO2(g) in aqueous (D2O) and methanolic (CD3OD) solutions. The reactions were monitored using 1H NMR spectroscopy, and yielded dendrimers with a combination of terminal carbamate and terminal ammonium groups. In aqueous media the reaction was complicated by the generation of soluble carbonate and bicarbonate ions. The reaction was cleaner in CD3OD, where the larger G5 dendrimer solution formed a gel upon exposure to CO2(g). All reactions were reversible, and the trapped CO2 could be released by treatment with N2(g) and mild heating. These results highlight the importance of the polyamine dendrimer size in terms of driving changes to the solution’s physical properties (viscosity, gel formation) generated by exposure to CO2(g).

Encapsulation of L-Valine, D-Leucine and D-Methionine by Cucurbit[8]uril

The binding interactions of cucurbit[8]uril (Q[8]) with L-Valine, D-Leucine, and D-Methionine, both in aqueous solution and solid state, have been studied by 1H NMR spectroscopy and X-ray crystallography. 1H NMR...

Metabolite Fingerprinting Using 1H-NMR Spectroscopy and Chemometrics for Classification of Three Curcuma Species from Different Origins

Curcuma longa, Curcuma xanthorrhiza, and Curcuma manga have been widely used for herbal or traditional medicine purposes. It was reported that turmeric plants provided several biological activities such as antioxidant, anti-inflammatory, hepatoprotector, cardioprotector, and anticancer activities. Authentication of the Curcuma species is important to ensure its authenticity and to avoid adulteration practices. Plants from different origins will have different metabolite compositions because metabolites are affected by soil nutrition, climate, temperature, and humidity. 1H-NMR spectroscopy, principal component analysis (PCA), and orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were used for authentication of C. longa, C. xanthorrhiza, and C. manga from seven different origins in Indonesia. From the 1H-NMR analysis it was obtained that 14 metabolites were responsible for generating classification model such as curcumin, demethoxycurcumin, alanine, methionine, threonine, lysine, alpha-glucose, beta-glucose, sucrose, alpha-fructose, beta-fructose, fumaric acid, tyrosine, and formate. Both PCA and OPLS-DA model demonstrated goodness of fit (R2 value more than 0.8) and good predictivity (Q2 value more than 0.45). All OPLS-DA models were validated by assessing the permutation test results with high value of original R2 and Q2. It can be concluded that metabolite fingerprinting using 1H-NMR spectroscopy and chemometrics provide a powerful tool for authentication of herbal and medicinal plants.

Synthesis of a new furan-bearing triazine dichloride compound

Donor-acceptor compounds have been receiving increased attention lately, especially in opto-electronic applications. In this work, a novel compound named triazine-furan, comprised of a triazine acceptor moiety and a furan donor side group, was designed and synthesised for the first time. The influences of temperature and the feeding proportion of cyanuric chloride to furfurylamine were investigated to optimise the reaction yield and purification process. The synthesised compound was characterised using thin-layer chromatography (TLC), Fourier-transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR) spectroscopy.

Synthesis, Self-Assembly and Photoresponsive Behavior of Liquid Crystals Based on Azobenzene

A new amphiphilic surfactant (C4-Azo-C5-HDA) was formed by liquid crystals (LCs) based on azobenzene, whose structures were characterized by 1H-NMR spectroscopy. The reversible hydrogelation upon changes in temperature and light exposure was also studied. Under the irradiation of UV light, the trans-isomer of C4-Azo-C5-HDA rapidly photoisomerized to the cis-isomer, resulting in rapid disruption of the gel. The thermotropic liquid crystal behavior of the gelator was investigated via Differential Scanning Calorimetry (DSC) and Polarizing Optical Microscopy (POM). The biocompatibility experiment of multi-stimulus response of the liquid crystal provides a potential driving force for the development of biomaterials.

Exploiting Urazole’s Acidity for Fabrication of Hydrogels and Ion-Exchange Materials

In this study, the acidity of urazole (pKa 5–6) was exploited to fabricate a hydrogel in two simple and scalable steps. Commercially available poly(hexamethylene)diisocyanate was used as a precursor to synthesize an urazole containing gel. The formation of urazole was confirmed by FT-IR and 1H-NMR spectroscopy. The hydrogel was characterized by microscopy imaging as well as spectroscopic and thermo-gravimetric analyses. Mechanical analysis and cell viability tests were performed for its initial biocompatibility evaluation. The prepared hydrogel is a highly porous hydrogel with a Young’s modulus of 0.91 MPa, has a swelling ratio of 87%, and is capable of exchanging ions in a medium. Finally, a general strategy was demonstrated to embed urazole groups directly into a crosslinked material.

Synthesis and properties of maleopimaric acid amides, imides and imidoamides with arylisoxazole and quinoline fragments

The method for maleopimaric acid N-(5-arylisoxazol-3-yl)amides synthesis has been developed by reaction of maleopimaric acid chloride with 3-amine-5-phenyl(4-methylphenyl)isoxazoles. N’-butyl-, N’-(2-hydroxyethyl)imides of maleopimaric acid N-(5-arylisoxazol-3-yl)amides were prepared. Heterocyclic imide – maleopimaric acid N-(quinolin-8-yl) imide was prepared by reaction of maleopimaric acid and 8-aminoquinoline in toluene at reflux in 97.1 % yield. It was established that refluxing of toluene solution of 8-aminoquinoline and maleated rosin, prepared by treatment of rosin with maleic anhydride and containing at least 50 % of maleopimaric acid, leads to the formation of maleopimaric acid N-(quinolin-8-yl)imide in 52.5 % yield (based on weight of maleated rosin). It was found by the methods of IR-, 1H NMR spectroscopy and mass-spectrometry that maleopimaric acid N-(quinolin-8-yl)imide consists of two diastereomeric atropisomers at 1:0.40 ratio. The biological properties of the prepared compounds were studied. It was established that maleopimaric acid N-(5-(4-methylphenyl)isoxazol-3-yl)amide possesses rotatory power (26 mkm-1) and may be used as chiral dopant to nematic LC for preparation of chiral LC-compositions.

Synthesis and Evaluation of Anti-inflammatory Activity of some Thiazolo[4,5-b]pyridines

The 18 new thiazolo[4,5-b]pyridin-2-one derivatives have been synthesized using alkylation, cyanethylation, hydrolysis, and acylation reactions. The structures of the obtained compounds have been confirmed by 1H NMR spectroscopy, mass spectrometry, and elemental analysis. The study of the in vivo anti-inflammatory activity of the synthesized substances was assessed by using the functional model of carrageenan-induced rat paw edema. The present results of anti-inflammatory activity have shown that the synthesized compounds demonstrated considerable anti-inflammatory effects. Some of them approach or exceed the comparative drug Ibuprofen in terms of activity.