NMR Spectroscopy as a Tool for Studying Asphaltene Composition

Asphaltenes are the most polar oil components with molecular weights between 500 and 1000 Da, which primarily consist of carbons and hydrogens, some heteroatoms, such as nitrogen, sulphur, oxygen and traces of nickel, vanadium and iron. Owing to their extreme complexity, it is almost impossible to completely identify all the compounds present in asphaltene samples. Various analytical techniques and approaches were used to characterize asphaltenes but their structure and composition are still a matter of thorough investigations. NMR spectroscopy can reveal useful information on asphaltene molecular architecture and aggregation process. In that respect, one- and two-dimensional NMR techniques have widely been employed. Although NMR spectra of these complex mixtures are difficult to interpret, they still can provide valuable data, especially in combination with statistical methods. Some distinctive examples of using NMR spectroscopy to study asphaltenes are given in this review. This work is licensed under a Creative Commons Attribution 4.0 International License

Rapid identification of bioactive carbohydrazide reaction products by an LC-DAD-SPE-NMR approach

On-line coupling of high performance liquid chromatography with diode array detection to solid phase extraction combined with nuclear magnetic resonance (LC-DAD-SPE-NMR) was used to monitor carbohydrazide condensation reaction progress. First, a chromatographic method was developed and optimised and individual peak separation was readily achieved by using an isocratic acetonitrile-phosphate buffer mobile phase. Subsequently, separated compounds were trapped on SPE cartridges and dried with nitrogen gas. Peak elution was then performed with deuterated acetonitrile and sent for NMR analysis. Single and multiple trapping options were applied. One- and two-dimensional NMR spectra were recorded using a Prodigy cryoprobe. It was demonstrated that LC-DAD-SPE-NMR setup was proved very useful for rapid and unambiguous identification of the reaction products and for determination of their structure. By using Prodigy cryoprobe in NMR measurements we were able to detect and identify compounds present at microgram level thus proving a high sensitivity of this methodology for monitoring reactions of bioactive molecules and drugs

Synthesis, Structural Characterization and Hydrogen Bonding of Mono(salicylidene)carbohydrazide

The condensation reaction between carbohydrazide and salicylaldehyde in different solvents gave mono(salicylidene)carbohydrazide (1). The structure of 1 in solution has been determined by using experimental (NMR and UV spectroscopies and Mass spectrometry) and quantum chemical (DFT) me-thods. It has been demonstrated that 1 adopts the hydroxy-one tautomeric form which is in accordance with previously published results for the related systems. Changes in NMR chemical shifts and calculations have pointed towards a formation of intra- and intermolecular hydrogen bonds, the later being weaker and easily broken at higher temperatures. These results can further be exploited for better understanding of the role hydrogen bonds can play in bioactivity of related derivatives. (doi: 10.5562/cca2123

Rijetka lokalizacija neuroblastoma u zdjelici

Neuroblastom je najčešći ekstrakranijalni maligni solidni tumor kod djece koji se većinom pojavljuje u trbuhu (nadbubrežna žlijezda, simpatički lanac) i medijastinumu, dok su druge lokacije rijetke. Tumor se liječi kirurški, kemoterapijom i radioterapijom. U ovom članku prikazan je rijedak slučaj neuroblastoma sakralnog pleksusa u zdjelici 9-mjesečnog ženskog dojenčeta sa širenjem u desni ishijadični i opturatorni kanal. Učinjena je ekstirpacija tumora s paraaortalnom i ilijakalnom limfadenektomijom, dok je manji dio tumora zaostao u opturatornom otvoru jer bi pokušaj potpunog odstranjenja nosio visok rizik od neurološkog oštećenja. Pokušaj potpunog odstranjenja tumorskog tkiva nije preporučiv jer nosi visok rizik od znatnih neuroloških oštećenja, a ne poboljšava preživljenje

Bioactive Phenylenediamine Derivatives of Dehydroacetic Acid: Synthesis, Structural Characterization and Deuterium Isotope Effects

Several phenylenediamine derivatives of dehydroacetic acid, 3-acetyl-4-hydroxy-6-methyl-2Hpyran- 2-one have been synthesized and their structure elucidated by using NMR and IR spectroscopies and mass spectrometry. Spectral analyses have pointed toward the localized keto-amine form as the predominant tautomeric form in solution and solid-state which was in agreement with X-ray data. The relatively broad N–H stretching bands observed in IR spectra and significant N–H proton down-field and keto C=O up-field shifts in NMR spectra indicated the presence of intra-molecular hydrogen bonds in all studied compounds. In order to gain further insights into nature of these interactions in solution deuterated isotopomers have been prepared and deuterium isotope effects in 13C NMR spectra have been determined and analyzed. The magnitude and sign of isotope effects have confirmed the existence of intra-molecular hydrogen bonds. Observed differences in isotope effects reflected different hydrogen bond structure and dynamics in studied compounds. The results presented in this paper might help in better understanding of biological properties of the related compounds.(doi: 10.5562/cca1825

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Crystallization of the drug entacapone from binary solvent mixtures was monitored in situ using a Raman optical probe. The recorded Raman spectra and statistical analysis, which included the principal components method and indirect hard modeling made it possible to estimate the starting point of crystallization, to assess crystallization temperatures and to provide information on the polymorphic content of the mixture. It was established that crystallization temperatures were proportional to the volume content of the solvent in mixtures. The samples were also evaluated off-line via Raman spectroscopy and SWAXS. The collected data showed the presence of forms b and g in all solvent mixtures. In a toluene/methanol 30:70 mixture, in addition to forms b and g, at least one of the forms A, D or a was also indicated by SWAXS. The results have shown that the presence of a particular polymorph is strongly dependent on the nature and portion of the solvent in the binary solvent mixture

Fast real-time monitoring of entacapone crystallization and characterization of polymorphs via Raman spectroscopy, statistics and SWAXS

Crystallization of the drug entacapone from binary solvent mixtures was monitored in situ using Raman optical probe. The recorded Raman spectra and statistical analysis, which included the principal components method and indirect hard modeling made it possible to estimate the starting point of crystallization, to assess crystallization temperatures and to provide information on the polymorphic content in the mixture. It was established that the crystallization temperatures were proportional to the volume content of the solvent in the mixtures. The samples were also evaluated off-line via Raman spectroscopy and SWAXS. The collected data showed the presence of forms β and γ in all solvent mixtures. In toluene/methanol 30:70 mixture, in addition to forms β and γ at least one of the forms A, D or α was also indicated by SWAXS. The results have shown that the presence of a particular polymorph is strongly dependent on the nature and portion of the solvent in the binary solvent mixture

Improvement of the Nutraceutical Profile of Brewer’s Spent Grain after Treatment with Trametes versicolor

Brewer’s spent grain (BSG) is an important secondary raw material that provides a readily available natural source of nutraceuticals. It finds its largest application as animal feed and part of the human diet, while the future perspective predicts an application in the production of value-added products. In order to investigate a sustainable BSG treatment method, two BSG samples (BSG1 and BSG2) were evaluated as substrates for the production of hydrolytic (xylanase, β-glucosidase and cellulase) and lignolytic enzymes (laccase, manganese peroxidase and lignin peroxidase) by solid-state fermentation (SSF) with Trametes versicolor while improving BSG nutritional value. The biological treatment was successful for the production of all hydrolytic enzymes and laccase and manganese peroxidase, while it was unsuccessful for the production of lignin peroxidase. Because the two BSGs were chemically different, the Trametes versicolor enzymes were synthesized at different fermentation times and had different activities. Consequently, the chemical composition of the two BSG samples at the end of fermentation was also different. The biological treatment had a positive effect on the increase in protein content, ash content, polyphenolic compounds, and sugars in BSG1. In BSG2, there was a decrease in the content of reducing sugars. Cellulose, hemicellulose, and lignin were degraded in BSG1, whereas only cellulose was degraded in BSG2, and the content of hemicellulose and lignin increased. The fat content decreased in both samples. The safety-related correctness analysis showed that the biologically treated sample did not contain any harmful components and was therefore safe for use in nutritionally enriched animal feed