Evaluation of different extraction approaches for the determination of phenolic compounds and their metabolites in plasma by nanoLC-ESI-TOF-MS

Metabolomics Technologies for the Identification and Quantification of Dietary Phenolic Compound Metabolites: An Overview

In the search for natural products with properties that may protect against or slow down chronic and degenerative diseases (e.g., cancer, and cardiovascular and neurodegenerative conditions), phenolic compounds (PC) with benefits for human health have been identified. The biological effects of PC in vivo depend on their bioavailability, intestinal absorption, metabolism, and interaction with target tissues. The identification of phenolic compounds metabolites (PCM), in biological samples, after food ingestion rich in PC is a first step to understand the overall effect on human health. However, their wide range of physicochemical properties, levels of abundance, and lack of reference standards, renders its identification and quantification a challenging task for existing analytical platforms. The most frequent approaches to metabolomics analysis combine mass spectrometry and NMR, parallel technologies that provide an overview of the metabolome and high-power compound elucidation. In this scenario, the aim of this review is to summarize the pre-analytical separation processes for plasma and urine samples and the technologies applied in quantitative and qualitative analysis of PCM. Additionally, a comparison of targeted and non-targeted approaches is presented, not available in previous reviews, which may be useful for future metabolomics studies of PCM.

Identification and Quantification of Phenolic Compounds from Mexican Oregano (Lippia graveolens HBK) Hydroethanolic Extracts and Evaluation of Its Antioxidant Capacity

Plants have been used for thousands of years for various purposes because they have a wide variety of activities with biological significance. Mexican oregano is an aromatic plant of great importance to Mexico and north of Jalisco state as a spice with important economic value. Chromatographic identification and quantification of phenolic compounds and evaluation of their antioxidant activity were important tools to obtain a better characterization of this spice. Phytochemical analysis indicated the presence of flavonoids, triterpenes, saponins, quinones and tannins, the latter at high concentrations. Through chromatographic assays of Mexican oregano extracts, 62 compounds were identified, the major ones being quantified as: taxifolin, apigenin 7-O-glucoside, phlorizin, eriodictyol, quercetin, naringenin, hispidulin, pinocembrin, galangin and genkwanin (compound for the first time reported for this species). The results can be useful as a precedent to establish the bases of new quality characterization parameters and they have also suggested that Mexican oregano contains a wide variety of compounds with untapped importance for the development of new high value-added products.

A review of nanoscale LC-ESI for metabolomics and its potential to enhance the metabolome coverage

Liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) platforms are widely used to perform high throughput untargeted profiling of biological samples for metabolomics-based approaches. However, these LC-ESI platforms usually favour the detection of metabolites present at relatively high concentrations because of analytical limitations such as ion suppression, thus reducing overall sensitivity. To counter this issue of sensitivity, the latest in terms of analytical platforms can be adopted to enable a greater portion of the metabolome to be analysed in a single analytical run. Here, nanoflow liquid chromatography-nanoelectrospray ionisation (nLC-nESI), which has previously been utilised successfully in proteomics, is explored for use in metabolomic and exposomic research. As a discovery based field, the markedly increased sensitivity of these nLC-nESI platforms offer the potential to uncover the roles played by low abundant signalling metabolites (e.g. steroids, eicosanoids) in health and disease studies, and would also enable an improvement in the detection of xenobiotics present at trace levels in biological matrices to better characterise the chemical exposome. This review aims to give an insight into the advantages associated with nLC-nESI for metabolomics-based approaches. Initially we detail the source of improved sensitivity prior to reviewing the available approaches to achieving nanoflow rates and nanospray ionisation for metabolomics. The robustness of nLC-nESI platforms was then assessed using the literature available from a metabolomic viewpoint. We also discuss the challenging point of sample preparation which needs to be addressed to fully enjoy the benefits of these nLC-nESI platforms. Finally, we assess metabolomic analysis utilising nano scale platforms and look ahead to the future of metabolomics using these new highly sensitive platforms.

Improved high sensitivity analysis of polyphenols and their metabolites by nano-liquid chromatography-mass spectrometry

This study was conducted to assess the value of a high resolution, high mass accuracy time-of-flight analyzer in combination with nanoliquid chromatography for the analysis of polyphenols and their metabolites. The goal was to create a method that utilizes small volumes of biological fluids and provides a significant improvement in sensitivity compared with existing methods. Accordingly, nanoLC-MS and nanoLC-pseudo-multiple reaction monitoring (MRM) methods were developed that had a lower limit of quantification of 0.5 nM for several polyphenols and were linear over 2-3 orders of magnitude (R(2)>0.999). Using urine samples, the ability to observe and quantify polyphenols in such a complex biological fluid depended on much narrower mass windows (0.050 amu or less) on a TOF analyzer than those used on a quadrupole analyzer (0.7 amu). Although a greater selectivity was possible with the low mass resolution of a triple quadrupole instrument using the MRM approach, for the daidzein metabolite O-DMA, a chromatographically resolvable second peak could only be substantially reduced by using a 0.01 amu mass window. The advantage of a TOF analyzer for product ion data is that the whole MSMS spectrum is collected at high mass accuracy and MRM experiments are conducted in silico after the analysis.