Limited genotypic and geographic variability of 16-O-methylated diterpene content in Coffea arabica green beans.

The acknowledged marker of Robusta coffee, 16-O-methylcafestol (16-OMC), can be quantified by NMR as a mixture with 16-O-methylkahweol (16-OMK), which accounts for approximately 10% of the mixture. In the present study, we detected and quantified 16-O-methylated diterpenes (16-OMD) in 248 samples of green Coffea arabica beans by NMR. We did not observe any differences between genotypes introgressed by chromosomal fragments of Robusta and non-introgressed genotypes.

Metabisotopomics of triacylglycerols from animal origin: A simultaneous metabolomic and isotopic profiling using C INEPT.

In previous works, we developed a C NMR method for analyzing triacylglycerols in olive oil using an adiabatic refocused INEPT sequence. This allowed spectral acquisition to be done in only 8 min with sufficient precision for isotopic measurements. In the present study, we made use of the same methodology to investigate the potential of triacylglycerols as source of biomarkers in animal origin matrices.

Intramolecular isotope effects during permanganate oxidation and acid hydrolysis of methyl tert-butyl ether.

Stable isotopes have been widely used to monitor remediation of environmental contaminants over the last decades. This approach gives a good mechanistic description of natural or assisted degradation of organic pollutants, such as methyl tert-butyl ether (MTBE). Since abiotic degradation seems to be the most promising assisted attenuation method, the isotopic fractionation associated with oxidation and hydrolysis processes need to be further investigated in order to understand better these processes and make their monitoring more efficient.

Improved lipid mixtures profiling by H NMR using reference lineshape adjustment and deconvolution techniques.

of one-dimensional H NMR spectra of complex mixtures, such as lipids from natural extracts, is hampered by the small spectral width leading to a great number of overlapped signals. Additional complications including lineshape broadening and distortion may occur due to magnetic field inhomogeneity. Quantitation of such spectra is therefore challenging.

Cholesterol, a powerful C isotopic biomarker.

Cholesterol is related to many health diseases and is considered as a metabolic disorder biomarker. This compound, present in all food products of animal origin, can also be used as food authentication biomarker. In this work and for the first time, positional C isotope contents were determined for such a high molecular weight compound.

Position-specific N isotope analysis in organic molecules: A high-precision N NMR method to determine the intramolecular N isotope composition and fractionation at natural abundance.

The position-specific N isotope content in organic molecules, at natural abundance, is for the first time determined by using a quantitative methodology based on N Nuclear Magnetic Resonance (NMR) spectrometry. N NMR spectra are obtained by using an adiabatic "Full-Spectrum" INEPT sequence in order to make possible N NMR experiments with a high signal-to-noise ratio (>500), to reach a precision with a standard deviation below 1‰ (0.1%).

Determination of l-cysteine origin on the basis of its δN values.

The majority of l-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers. Despite widespread belief, there is little evidence that human hair is used as a source material and its use is explicitly banned in the European Union (2000/63/EC decision). We developed an isotope ratio mass spectrometric (EA-IRMS) method to determine carbon and nitrogen isotopic ratio in cysteine preparations and related compounds, e.

Olive oil characterization and classification by C NMR with a polarization transfer technique: A comparison with gas chromatography and H NMR.

In a previous work, we optimized and used a fast adiabatic C-INEPT (Insensitive Nuclei Enhanced by Polarization Transfer) experiment for the isotopomic analysis of olive oil samples, which allowed us quantifying individual fatty acids within triacylglycerols through multivariate linear regression models. The goal of this study was to validate these models and to evaluate the power of C-INEPT in the authentication of olive oils relative to gas chromatography (GC) and H NMR. In this respect, a new set of olive oil samples was analyzed by these three techniques.

Expanded uncertainty associated with determination of isotope enrichment factors: Comparison of two point calculation and Rayleigh-plot.

The enrichment factor (ε) is a common way to express Isotope Effects (IEs) associated with a phenomenon. Many studies determine ε using a Rayleigh-plot, which needs multiple data points. More recent articles describe an alternative method using the Rayleigh equation that allows the determination of ε using only one experimental point, but this method is often subject to controversy.

Natural Isotope Abundance in Metabolites: Techniques and Kinetic Isotope Effect Measurement in Plant, Animal, and Human Tissues.

The natural isotope abundance in bulk organic matter or tissues is not a sufficient base to investigate physiological properties, biosynthetic mechanisms, and nutrition sources of biological systems. In fact, isotope effects in metabolism lead to a heterogeneous distribution of H, O, C, and N isotopes in metabolites. Therefore, compound-specific isotopic analysis (CSIA) is crucial to biological and medical applications of stable isotopes.

Position-Specific C Fractionation during Liquid-Vapor Transition Correlated to the Strength of Intermolecular Interaction in the Liquid Phase.

The relationship between the strength of the intermolecular interaction in liquid and the position-specific C fractionation observed during distillation was investigated. A range of molecules showing different intermolecular interactions in terms of mode and intensity were incorporated in the study. Although it had previously been suggested that during evaporation the diffusive C isotope effect in the thin liquid layer interfaced with vapor is not position-specific, herein we show that this is not the case.

A strategy for simultaneous determination of fatty acid composition, fatty acid position, and position-specific isotope contents in triacylglycerol matrices by C-NMR.

Triacylglycerols, which are quasi-universal components of food matrices, consist of complex mixtures of molecules. Their site-specific C content, their fatty acid profile, and their position on the glycerol moiety may significantly vary with the geographical, botanical, or animal origin of the sample. Such variables are valuable tracers for food authentication issues.

C and N natural isotope abundance reflects breast cancer cell metabolism.

Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes.

Geoclimatic, morphological, and temporal effects on Lebanese olive oils composition and classification: A (1)H NMR metabolomic study.

Two hundred and thirty-four Lebanese olive samples were collected from different regions and the corresponding oils were analysed by (1)H NMR spectroscopy. The variables obtained, related to fatty acids and minor components, were used as inputs in univariate and multivariate analyses aiming to characterize and classify the oils according to geographical, morphological, and temporal factors. Samples were sorted according to the colour, size, and shape of olives, which allowed statistically significant classifications to be achieved.

Precise and rapid isotopomic analysis by (1)H-(13)C 2D NMR: Application to triacylglycerol matrices.

An optimized HSQC sequence was tested and applied to triacylglycerol matrices to determine their isotopic and metabolomic profiles. Spectral aliasing and non-uniform sampling approaches were used to decrease the experimental time and to improve the resolution, respectively. An excellent long-term repeatability of signal integrals was achieved enabling to perform isotopic measurements.

A Ring-D-Seco-Tetranortriterpenoid from Seeds of Carapa procera Active against Breast Cancer Cell Lines.

The seeds of Carapa procera are exploited extensively in West African ethnopharmacy for the treatment of several pathologies, including inflammation. They also are effective as insect antifeedants and as a mosquito repellent. With the aim of identifying bioactive principles, an ethyl acetate extract of the defatted seeds was made and fractionated.

Enhanced forensic discrimination of pollutants by position-specific isotope analysis using isotope ratio monitoring by (13)C nuclear magnetic resonance spectrometry.

In forensic environmental investigations the main issue concerns the inference of the original source of the pollutant for determining the liable party. Isotope measurements in geochemistry, combined with complimentary techniques for contaminant identification, have contributed significantly to source determination at polluted sites. In this work we have determined the intramolecular (13)C profiles of several molecules well-known as pollutants.

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis.

Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position-specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol.

Suppression of radiation damping for high precision quantitative NMR.

True quantitative analysis of concentrated samples by (1)H NMR is made very difficult by Radiation Damping. A novel NMR sequence (inspired by the WET NMR sequence and by Outer Volume Saturation methods) is therefore proposed to suppress this phenomenon by reducing the spatial area and consequently the number of spins contributing to the signal detected. The size of the detected volume can be easily chosen in a large range and line shape distortions are avoided thanks to a uniform signal suppression of the outer volume.

Internal Referencing for ¹³C Position-Specific Isotope Analysis Measured by NMR Spectrometry.

The intramolecular (13)C composition of a molecule retains evidence relevant to its (bio)synthetic history and can provide valuable information in numerous fields ranging from biochemistry to environmental sciences. Isotope ratio monitoring by (13)C NMR spectrometry (irm-(13)C NMR) is a generic method that offers the potential to conduct (13)C position-specific isotope analysis with a precision better than 1‰. Until now, determining absolute values also required measurement of the global (or bulk) (13)C composition (δ(13)Cg) by mass spectrometry.

Fractionation in position-specific isotope composition during vaporization of environmental pollutants measured with isotope ratio monitoring by ¹³C nuclear magnetic resonance spectrometry.

Isotopic fractionation of pollutants in terrestrial or aqueous environments is a well-recognized means by which to track different processes during remediation. As a complement to the common practice of measuring the change in isotope ratio for the whole molecule using isotope ratio monitoring by mass spectrometry (irm-MS), position-specific isotope analysis (PSIA) can provide further information that can be exploited to investigate source and remediation of soil and water pollutants. Position-specific fractionation originates from either degradative or partitioning processes.

Conditions to obtain precise and true measurements of the intramolecular 13C distribution in organic molecules by isotopic 13C nuclear magnetic resonance spectrometry.

Intramolecular (13)C composition gives access to new information on the (bio) synthetic history of a given molecule. Isotopic (13)C NMR spectrometry provides a general tool for measuring the position-specific (13)C content. As an emerging technique, some aspects of its performance are not yet fully delineated.

Biochemical and physiological determinants of intramolecular isotope patterns in sucrose from C₃, C₄ and CAM plants accessed by isotopic ¹³C NMR spectrometry: a viewpoint.

This paper discusses the biochemical and physiological factors underlying the site-specific, non-random distribution of ¹³C/¹²C isotope ratios within plant metabolites, which can be determined by isotopic ¹³C NMR spectrometry. It focuses on the key metabolite glucose and on enzyme activities and physiological processes that are responsible for the carbon isotope patterns in glucose from different biological origins. It further considers how intramolecular ¹³C/¹²C isotope ratios in glucose can be exploited to understand fundamental aspects of plant biological chemistry, how these are related to environmental parameters and how these influence metabolites beyond central sugar metabolism.

1H-NMR-based metabolic profiling of maternal and umbilical cord blood indicates altered materno-foetal nutrient exchange in preterm infants.

Background: Adequate foetal growth is primarily determined by nutrient availability, which is dependent on placental nutrient transport and foetal metabolism. We have used (1)H nuclear magnetic resonance (NMR) spectroscopy to probe the metabolic adaptations associated with premature birth.

Methodology: The metabolic profile in (1)H NMR spectra of plasma taken immediately after birth from umbilical vein, umbilical artery and maternal blood were recorded for mothers delivering very-low-birth-weight (VLBW) or normo-ponderal full-term (FT) neonates.

The intramolecular ¹³C-distribution in ethanol reveals the influence of the CO₂ -fixation pathway and environmental conditions on the site-specific ¹³C variation in glucose.

Efforts to understand the cause of ¹²C versus ¹³C isotope fractionation in plants during photosynthesis and post-photosynthetic metabolism are frustrated by the lack of data on the intramolecular ¹³C-distribution in metabolites and its variation with environmental conditions. We have exploited isotopic carbon-13 nuclear magnetic resonance (¹³C NMR) spectrometry to measure the positional isotope composition (δ¹³C(i) , ‰) in ethanol samples from different origins: European wines, liquors and sugars from C₃, C₄ and crassulacean acid metabolism (CAM) plants. In C₃-ethanol samples, the methylene group was always ¹³C-enriched (∼2‰) relative to the methyl group.