Application Of 1H NMR Spectroscopy Research Articles

Novel application of 1H NMR spectroscopy coupled with chemometrics for the authentication of dark chocolate

The applicability of 1H NMR spectroscopy coupled with chemometric in the quality control of dark chocolate was investigated for the first time to detect cocoa-butter equivalents (CBEs) above the allowed limit by European regulation. Blends of chocolate-fats with CBEs in the range 0–50 % were prepared and analyzed by 1H NMR spectroscopy. Datasets composed of peaks’ areas or spectral variables (fingerprinting) in glycerol region were tested for the creation of multivariate statistical models. Partial least-squares discriminant analysis (PLS-DA) and regression (PLS-R) methods were used to correctly identify the type of CBE and quantify its concentration respectively. The performances of the models created on the two datasets were evaluated in terms of chemometric indicators and compared. The robustness of models was investigated through the analysis of test sets and random permutation tests. Fingerprinting models revealed fruitful results in classifying and quantifying CBEs in blends demonstrating the applicability of NMR in chocolate quality control.

The First Application of 1H NMR Spectroscopy for the Assessment of the Authenticity of Perfumes.

The manufacture of counterfeit goods is one of the world’s largest underground businesses and is rapidly growing. Counterfeits can lead not only to the loss of profit for honest producers but also have a negative impact on consumers who pay excessive prices for poor quality goods that may result in health or safety problems. The perfume industry is constantly vulnerable to counterfeits, particularly in the fast developing market of “smell-alike” designer-inspired perfumes because these prompt the identification of the methods that classify their quality. In this paper, the application of proton nuclear magnetic resonance (1H NMR) spectroscopy is employed for the first time to authenticate perfumery products. The molecular composition of several types of authentic brand fragrances for women was compared with cheap inspired equivalents and fakes. Our approach offers the prospect of a fast and simple method for detecting counterfeit perfumes using 1H NMR spectroscopy.

1H NMR profiling and chemometric analysis as an approach to predict the leishmanicidal activity of dichloromethane extracts from Lantana camara (L.)

The application of 1H NMR spectroscopy and chemometrics for the analysis of extracts of Lantana camara is described. This approach allowed to predict the leishmanicidal activity of samples obtained at different harvest times from their 1H NMR spectra. The anti–leishmanial activity of dichloromethane extracts obtained from the aerial parts of L. camara was measured using an in vitro assay. As the extracts displayed differences in their activity according to a one–way ANOVA analysis, their 1H NMR spectra were subjected to multivariate analysis using exploratory (Principal Component Analysis (PCA) and Anova Simultaneous Component Analysis (ASCA)) and regression, (Partial Least Squares Regression to Latent Structures (PLS)) chemometrics methods. These analyses allowed to establish and characterize a predictive model capable of determining the anti–leishmanial activity of Lantana camara dichloromethane extracts from their 1H NMR spectra. Figures of merit of the developed method are given as well. The identified chemical signals responsible for the iPLS calibration model corresponded to the presence of eicosane, caryophyllene oxide, β-ionone, tiglic acid, lantanilic acid, camaric acid, and lantadene B; the chemical markers. This study proposed a fast and simple method that avoids the need of using complex biological assays to predict the leishmanicidal activity of L. camara dichloromethane extracts.

Quantifying the Product Distribution of a Chemical Reaction by 1H NMR Spectroscopy: A Cooperative Learning Approach for the Undergraduate Organic Chemistry Laboratory

This enhancement of a classic laboratory experiment investigates the kinetic and thermodynamic control of a reaction utilizing 1H NMR spectroscopy instead of melting point analysis to determine the product distribution. In this experiment, semicarbazide is reacted with cyclohexanone and 2-furaldehyde under varying buffer and temperature conditions to yield semicarbazone derivative products. After 1H NMR analysis of the products, students compile the class data in a cooperative setting facilitated by graduate teaching assistants. As a result, students are able to analyze a larger data set in this cooperative learning environment in order to describe the product distribution of the reaction on the basis of trends as opposed to using a single data set. The application of 1H NMR spectroscopy to determine the product distribution of the reaction introduces a modern approach to study a well-established example of the kinetic and thermodynamic control of a reaction.

Application of 1H NMR spectroscopy to the metabolic phenotyping of rodent brain extracts: A metabonomic study of gut microbial influence on host brain metabolism

1H NMR Spectroscopy has been applied to determine the neurochemical profiles of brain extracts from the frontal cortex and hippocampal regions of germ free and normal mice and rats. The results revealed a number of differences between germ free (GF) and conventional (CV) rats or specific pathogen-free (SPF) mice with microbiome-associated metabolic variation found to be both species- and region-dependent. In the mouse, the GF frontal cortex contained lower amounts of creatine, N-acetyl-aspartate (NAA), glycerophosphocholine and lactate, but greater amounts of choline compared to that of specific pathogen free (SPF) mice. In the hippocampus, the GF mice had greater creatine, NAA, lactate and taurine content compared to those of the SPF animals, but lower relative quantities of succinate and an unidentified lipid-related component. The GF rat frontal cortex contained higher relative quantities of lactate, creatine and NAA compared to the CV animals whilst the GF hippocampus was characterized by higher taurine and phosphocholine concentrations and lower quantities of NAA, N-acetylaspartylglutamate and choline compared to the CV animals. Of note is that, in both rat and mouse brain extracts, concentrations of hippocampal taurine were found to be greater in the absence of an established microbiome. The results provide further evidence that brain biochemistry can be influenced by gut microbial status, specifically metabolites involved in energy metabolism demonstrating biochemical dialogue between the microbiome and brain.

1H NMR spectral identification of medication in cerebrospinal fluid of pediatric meningitis

Exploratory metabolomics studies of cerebrospinal fluid (CSF), using proton nuclear magnetic resonance (1H NMR) spectroscopy, hold major potential application in neurodiagnostics. Such studies, however, rely upon established databases of known metabolites. Here we address the ‘unknowns’ in the 1H NMR spectra of CSF from treated pediatric meningitis cases. Through knowledge of the clinical information given by the pediatrician and analytical application of 1H NMR spectroscopy on pure reference compounds of the medication used, we identified four of the previously unknown compounds in the 1H NMR CSF spectra — the drugs pyrazinamide, isoniazid, acyclovir, and sulfamethoxazole. We report on the one- and two-dimensional 1H NMR spectral data and chemical information of these four compounds. By expanding our knowledge of 1H NMR CSF spectra from treated meningitis cases, we are able to bring 1H NMR closer to the forefront of neurodiagnostics.

Detection of adulteration in Iranian saffron samples by 1H NMR spectroscopy and multivariate data analysis techniques

The high market value of saffron (Crocus sativus L.) has made it an attractive candidate for adulteration. Safflower (Carthamus tinctorius L.) and tartrazine are among the most common herbal and synthetic foreign materials that may be added to pure saffron for the purpose of adulteration. In spite of encouraging advances achieved in the identification of adulteration in saffron samples, the lack of a simple method with sufficient power for discrimination of pure high grade saffron from meticulously adulterated saffron samples persuaded us to perform this study. In this work, we show that 1H NMR spectroscopy together with chemometric multivariate data analysis methods can be used for the detection of adulteration in saffron. Authentic Iranian saffron samples (n = 20) and adulterated samples that were prepared by adding either different quantities of natural plant materials such as safflower, or synthetic dyes such as tartrazine or naphthol yellow to pure saffron (n = 22) composed the training set. This training set was used to build multivariate Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA) models. The predictive power of the PLS-DA model was validated by testing the model against an external dataset (n = 13). PCA and PLS-DA models could both discriminate between the authentic and adulterated samples, and the external validation showed 100% sensitivity and specificity for predicting the authenticity of suspicious samples. Peaks specific to authentic and adulterated samples were also characterized. Proximity of samples with unknown adulteration status to the samples adulterated with known compounds in the PCA provided insight regarding the identity of the adulterant in the suspicious samples. Furthermore, the authentic samples could be distinguished based on their cultivation site. The present study demonstrates that the application of 1H NMR spectroscopy coupled with multivariate data analysis is a suitable approach for detection of adulteration in saffron specimens. Outstanding sensitivity and specificity of the PLS-DA model in discriminating the authentic from adulterated samples in external validation confirmed the high predictive power of the model. The advantage of the present method is its power for detecting a wide spectrum of adulterants, ranging from synthetic dyes to herbal materials, in a single assay.

1H NMR application in characterizing the refinery products of gasoline

AbstractWe report on an application of 1H NMR spectroscopy in characterizing the gasoline properties of its refinery products. In this work, a variety of gasoline samples obtained from different refinery stages are studied, and the aromatic, olefin, and paraffin contents as well as the octane number (ON) of the gasoline samples are characterized by 1H NMR. The properties of two product gasoline samples are also studied by 1H NMR spectroscopy; the NMR‐determined values for the ONs are compared with the research octane number values measured in a standard test engine, and a good agreement is achieved. This work indicates that the characteristics of gasoline can be revealed by 1H NMR, and the values derived from the NMR spectroscopy can be used to assess the gasoline quality during its refinery processes. Based on this work, we demonstrate that the 1H NMR spectroscopy is a convenient tool in the continuous monitoring of the refinery processes of gasoline.

GRAPE JUICE QUALITY CONTROL BY MEANS OF1H NMR SPECTROSCOPY AND CHEMOMETRIC ANALYSES

This work shows the application of 1H NMR spectroscopy and chemometrics for quality control of grape juice. A wide range of quality assurance parameters were assessed by single 1H NMR experiments acquired directly from juice. The investigation revealed that conditions and time of storage should be revised and indicated on all labels. The sterilization process of homemade grape juices was efficient, making it possible to store them for long periods without additives. Furthermore, chemometric analysis classified the best commercial grape juices to be similar to homemade grape juices, indicating that this approach can be used to determine the authenticity after adulteration.

Synthesis and diuretic properties of n-aryl- 6-hydroxy-2-methyl-4-oxo-2,4-dihydro-1h-pyrrolo [3,2,1-ij]quinoline-5-carboxamides with electron-acceptor substituents in the anilide fragment

In numerous studies of 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamides it has been convincingly shown that amidation of quinoline-3-carboxylic acids esters with alkyl-, aryl- and hetarylamines is the best way to obtain these compounds. As a rule, syntheses proceed smoothly and efficiently under rather mild conditions. However, in those cases when for formation of amides the temperature of 120-150°C and above is applied, partial destruction of the ester fragment may occur and, as a result, it pollutes the target products with specific impurities – the corresponding 4-hydroxy-1,2- dihydroquinolin-2-ones or their analogues. Application of 1H NMR spectroscopy allows to prove that the cause of ester fragments destruction, which sometimes can be observed when alkyl 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylates react with amines under harsh conditions, is water presented in the reagents or in the solvents. It becomes clear from this study that at the temperature of 95°C and higher the sensitivity of 4-hydroxy-2-oxo-1,2-dihydroquinoline- 3-carboxylic acids esters in a solution or a melt to hydrolysis increases significantly. Simple methods to minimize this undesirable process have been proposed – if the synthesis of N-substituted amides based on them requires such severe conditions, water should be removed from the reagents and solvents in order to avoid contamination of the final products with 4-hydroxy-1,2-dihydroquinolin-2-ones. The results of the diuretic properties study of new substituted anilides of 6-hydroxy-2-methyl-4-oxo-2,4-dihydro-1H-pyrrolo[3,2,1-ij]quinoline-5-carboxylic acid are discussed.

The neurochemical profile quantified by in vivo 1H NMR spectroscopy

Proton NMR spectroscopy is emerging from translational and preclinical neuroscience research as an important tool for evidence based diagnosis and therapy monitoring. It provides biomarkers that offer fingerprints of neurological disorders even in cases where a lesion is not yet observed in MR images. The collection of molecules used as cerebral biomarkers that are detectable by (1)H NMR spectroscopy define the so-called "neurochemical profile". The non-invasive quality of this technique makes it suitable not only for diagnostic purposes but also for therapy monitoring paralleling an eventual neuroprotection. The application of (1)H NMR spectroscopy in basic and translational neuroscience research is discussed here.

Liquid-phase combinatorial reaction monitoring by conventional 1H NMR spectroscopy

The application of 1H NMR spectroscopy for complete analysis of soluble polymer-supported reactions is described. This conventional analytical technique enables us to determine the extent of liquid-phase reactions without cleavage of the soluble matrix. The polymer matrix permitted us to obtain 1H NMR spectra with a resolution comparable with that of spectra of the molecule in solution.

APPLICATION OF NMR SPECTROSCOPY TO ASSESS OXIDATIVE STABILITY OF CANOLA AND SOYBEAN OILS

ABSTRACT.Application of 1H NMR spectroscopy to monitor oxidation of canola and soybean oils was investigated over a 30‐day period at 65C. Relative changes of aliphatic to olefinic (Rao) and aliphatic to diallylmethylene (Rad) proton ratios during oxidation of these oils were calculated. A steady increase in Rao and Rad values was observed over the entire length of the storage period. A highly significant correlation (r = 0.933 – 0.985) existed between the TOTOX value and changes in the Rao and Rad during oxidation of both oils. Therefore, NMR offers a novel method to assess oxidative stability of vegetable oils such as canola and soybean.

Terminal α(1→4)-linked N-acetylglucosamine: A characteristic constituent of doudenal-gland mucous glycoproteins in rat and pig : A high-resolution 1H-NMR study

The structure of the carbohydrate chains of mucous glycoproteins from the gastro-intestinal tract was examined for species- and tissue-specificity. To this purpose, oligosaccharides were released from purified glycoprotein preparations of rat and pig gastric, duodenal-gland and small-intestinal mucus, by alkaline borohydride reductive cleavage. Based on the results of 500-MHz 1H-NMR spectroscopy and of sugar analysis of the total oligosaccharide fractions, terminal GlcNAc, α(1→4)-linked to galactose, appears to be a characteristic constituent of duodenal-gland oligosaccharides. Similarly, NeuAc in α(2→3)-linkage to galactose turns out to be a typical constituent of small-intestinal mucous glycoproteins. In general, glycoproteins from gastric mucus possess larger and more-branched carbohydrate chains than those from duodenal-gland and small-intestinal mucus. Comparing rat and pig, oligosaccharide structures for corresponding tissues are less complex for the former. After fractionation, the rat duodenal-gland oligosaccharides could be characterized by application of 1H-NMR spectroscopy as being branched tetra- up to hexa-saccharide chains, all sharing the italicized trisaccharide element. The chains exhibit microheterogeneity as to the termination by fucose in α(1→2)- or by GlcNAc in α(1→4)-linkage to galactose. The following structures can be proposed for the most abundant rat duodenal-gland oligosaccharides: ▪