Simple and Rapid (Extraction) Protocol for NMR Metabolomics-Direct Measurement of Hydrophilic and Hydrophobic Metabolites Using Slice Selection

Cutting without a Knife: A Slice-Selective 2D 1H-13C HSQC NMR Sequence for the Analysis of Inhomogeneous Samples

Nuclear magnetic resonance (NMR) is a powerful technique with applications ranging from small molecule structure elucidation to metabolomics studies of living organisms. Typically, solution-state NMR requires a homogeneous liquid, and the whole sample is analyzed as a single entity. While adequate for homogeneous samples, such an approach is limited if the composition varies as would be the case in samples that are naturally heterogeneous or layered. In complex samples such as living organisms, magnetic susceptibility distortions lead to broad 1H line shapes, and thus, the additional spectral dispersion afforded by 2D heteronuclear experiments is often required for metabolite discrimination. Here, a novel, slice-selective 2D, 1H-13C heteronuclear single quantum coherence (HSQC) sequence was developed that exclusively employs shaped pulses such that only spins in the desired volume are perturbed. In turn, this permits multiple volumes in the tube to be studied during a single relaxation delay, increasing sensitivity and throughput. The approach is first demonstrated on standards and then used to isolate specific sample/sensor elements from a microcoil array and finally study slices within a living earthworm, allowing metabolite changes to be discerned with feeding. Overall, slice-selective NMR is demonstrated to have significant potential for the study of layered and other inhomogeneous samples of varying complexity. In particular, its ability to select subelements is an important step toward developing microcoil receive-only arrays to study environmental toxicity in tiny eggs, cells, and neonates, whereas localization in larger living species could help better correlate toxin-induced biochemical responses to the physical localities or organs involved.

Innovative Application of Metabolomics on Bioactive Ingredients of Foods

Metabolomics, as a new omics technology, has been widely accepted by researchers and has shown great potential in the field of nutrition and health in recent years. This review briefly introduces the process of metabolomics analysis, including sample preparation and extraction, derivatization, separation and detection, and data processing. This paper focuses on the application of metabolomics in food-derived bioactive ingredients. For example, metabolomics techniques are used to analyze metabolites in food to find bioactive substances or new metabolites in food materials. Moreover, bioactive substances have been tested in vitro and in vivo, as well as in humans, to investigate the changes of metabolites and the underlying metabolic pathways, among which metabolomics is used to find potential biomarkers and targets. Metabolomics provides a new approach for the prevention and regulation of chronic diseases and the study of the underlying mechanisms. It also provides strong support for the development of functional food or drugs. Although metabolomics has some limitations such as low sensitivity, poor repeatability, and limited detection range, it is developing rapidly in general, and also in the field of nutrition and health. At the end of this paper, we put forward our own insights on the development prospects of metabolomics in the application of bioactive ingredients in food.

A one-shot double-slice selection NMR method for biphasic systems

We propose a new and robust one-shot double-slice selection experiment to detect 1H NMR signals of biphasic systems simultaneously. The resultant spectrum contains opposite-phased peaks representing the chemical species from the two phases, respectively.

Ultrahigh-Resolution NMR with Water Signal Suppression for a Deeper Understanding of the Action of Antimetabolic Drugs on Diffuse Large B-Cell Lymphoma

Ultrahigh-resolution NMR has recently attracted considerable attention in the field of complex samples analysis. Indeed, the implementation of broadband homonuclear decoupling techniques has allowed us to greatly simplify crowded ¹H spectra, yielding singlets for almost every proton site from the analyzed molecules. Pure shift methods have notably shown to be particularly suitable for deciphering mixtures of metabolites in biological samples. Here, we have successfully implemented a new pure shift pulse sequence based on the PSYCHE method, which incorporates a block for solvent suppression that is suitable for metabolomics analysis. The resulting experiment allows us to record ultrahigh-resolution 1D NOESY ¹H spectra of biofluids with suppression of the water signal, which is a crucial step for highlighting metabolite mixtures in an aqueous phase. We have successfully recorded pure shift spectra on extracellular media of diffuse large B-cell lymphoma (DLBCL) cells. Despite a lower sensitivity, the resolution of pure shift data was found to be better than that of the standard approach, which provides a more detailed vision of the exo-metabolome. The statistical analyses carried out on the resulting metabolic profiles allow us to successfully highlight several metabolic pathways affected by these drugs. Notably, we show that Kidrolase plays a major role in the metabolic pathways of this DLBCL cell line.

Accelerated 13C detection by concentrating the NMR sample in a biphasic solvent system

CDCl₃ is the most frequently used solvent for the NMR investigation of organic compounds. Busy chemistry labs need to investigate hundreds of compounds daily. While ¹H NMR investigation takes a couple of minutes, recording ¹³C NMR spectra necessitates hours of signal averaging due to the low abundance and low sensitivity of ¹³C nuclei. The longer acquisition time for ¹³C NMR results in a loss of precious spectrometer time in a shared multi-user environment. A regular 5 mm o.d. NMR tube is the most commonly used tube for NMR in organic chemistry labs and is also the cheapest option. We show that for analytes soluble in the CDCl₃ solvent using a regular 5 mm o.d. NMR tube, the speed of ¹³C observation can be enhanced by a factor of two by resorting to a sample preparation method that employs a biphasic system made of H₂O or D₂O at the top of another layer of CDCl₃. By using the biphasic system of two immiscible solvents, the analyte can be concentrated in the CDCl₃ layer (within the more sensitive volume of the NMR coil), resulting in the improvement of the signal to noise ratio (SNR) by a factor of up to 1.8 for ¹³C and 2D ¹H-¹³C HSQC spectra, which results in more than two-fold reduction in the experimental time. ¹H NMR and other 2D NMR also get a sensitivity boost. The amount of CDCl₃ required for sample preparation can also be reduced by 40% using this biphasic system (CDCl₃/H₂O). Sample preparation in such an immiscible biphasic system is effortless and straightforward. The performance of such biphasic samples is closer to that of Shigemi tubes and better than that of 3 mm o.d. tubes.