Suspect screening of glycoalkaloids in plant extracts using neutral loss – High resolution mass spectrometry

Mass spectrometric analysis strategies for pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) in food and natural preparations have received widespread attention due to their hepatotoxicity, genotoxicity, and embryotoxicity. Mass spectrometry (MS), as a high resolution, high sensitive, and high throughput detection tool, has been the most commonly used technique for the determination of PAs. The continuous advancement of new technologies, methods, and strategies in the field of MS has contributed to the improvement of the analytical efficiency and methodological enhancement of PAs. This paper provides an overview of the structure, toxicity properties and commonly employed analytical methods, focusing on the concepts, advances, and novel techniques and applications of MS-based methods for the analysis of PAs. Additionally, the remaining challenges, future perspectives, and trends for PA detection are discussed. This review provides a reference for toxicological studies of PAs, content monitoring, and the establishment of quality control and safety standards for herbal and food products.

Exploration of the Diversity of Vicine and Convicine Derivatives in Faba Bean (Vicia faba L.) Cultivars: Insights from LC-MS/MS Spectra

While numerous Fabaceae seeds are a good nutritional source of high-quality protein, the use of some species is hampered by toxic effects caused by exposure to metabolites that accumulate in the seeds. One such species is the faba or broad bean (Vicia faba L.), which accumulates vicine and convicine. These two glycoalkaloids cause favism, the breakdown of red blood cells in persons with a glucose-6-phosphate dehydrogenase deficiency. Because this is the most common enzyme deficiency worldwide, faba bean breeding efforts have focused on developing cultivars with low levels of these alkaloids. Consequently, quantification methods have been developed; however, they quantify vicine and convicine only and not the derivatives of these compounds that potentially generate the same bio-active molecules. Based on the recognition of previously unknown (con)vicine-containing compounds, we screened the fragmentation spectra of LC-MS/MS data from five faba bean cultivars using the characteristic fragments generated by (con)vicine. This resulted in the recognition of more than a hundred derivatives, of which 89 were tentatively identified. (Con)vicine was mainly derivatized through the addition of sugars, hydroxycinnamic acids, and dicarboxylic acids, with a group of compounds composed of two (con)vicine residues linked by dicarboxyl fatty acids. In general, the abundance profiles of the different derivatives in the five cultivars mimicked that of vicine and convicine, but some showed a derivative-specific profile. The description of the (con)vicine diversity will impact the interpretation of future studies on the biosynthesis of (con)vicine, and the content in potentially bio-active alkaloids in faba beans may be higher than that represented by the quantification of vicine and convicine alone.

Mass spectrometry-based metabolomic analysis as a tool for quality control of natural complex products

Metabolomics is an area of intriguing and growing interest. Since the late 1990s, when the first Omic applications appeared to study metabolite's pool ("metabolome"), to understand new aspects of the global regulation of cellular metabolism in biology, there have been many evolutions. Currently, there are many applications in different fields such as clinical, medical, agricultural, and food. In our opinion, it is clear that developments in metabolomics analysis have also been driven by advances in mass spectrometry (MS) technology. As natural complex products (NCPs) are increasingly used around the world as medicines, food supplements, and substance-based medical devices, their analysis using metabolomic approaches will help to bring more and more rigor to scientific studies and industrial production monitoring. This review is intended to emphasize the importance of metabolomics as a powerful tool for studying NCPs, by which significant advantages can be obtained in terms of elucidation of their composition, biological effects, and quality control. The different approaches of metabolomic analysis, the main and basic techniques of multivariate statistical analysis are also briefly illustrated, to allow an overview of the workflow associated with the metabolomic studies of NCPs. Therefore, various articles and reviews are illustrated and commented as examples of the application of MS-based metabolomics to NCPs.

Profiling of pyrrolizidine alkaloids using a retronecine-based untargeted metabolomics approach coupled to the quantitation of the retronecine-core in medicinal plants using UHPLC-QTOF

Pyrrolizidine alkaloids (PA) are secondary metabolites of high toxicological relevance. Several PA quantitative methodologies were developed based on a limited number of certified standards, including time consuming solid phase extraction (SPE) purification steps. Herein, we shed light on the variability of PA in herbal extracts and propose a quantification methodology based on ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS) for the evaluation of the total PA content as retronecine-equivalents (RE) directly from crude matrices. Particularly in the focus of the investigation were Alkanna spp. (Boraginaceae), which possess a wide range of pharmaceutical properties. In addition, a comparative PA screening of crude and SPE enriched extracts was performed and PA-containing plants from Fabaceae and Compositae families were included to demonstrate universal applicability. In total, 105 PA were identified using HRMS^e experiments, specific MS/MS fragmentation PA patterns, a customized in-house library and literature data. Among them, 18 glycosidic PA derivatives were reported for the first time in literature. Using a hierarchical clustering approach, PA distribution in herbal extracts was shown to be family-dependent and significantly different among species. This was further supported by the results of the total PA concentrations, obtained using a retronecine/heliotridine/internal standard-based targeted UHPLC-HRMS quantification method, which varied from 8.64 ± 0.08-3096.28 ± 273.72 μg RE/g extract dry weight in shoots extracts of Alkanna spp. and leaves extracts of Crotalaria retusa L. respectively. Worth mentioning is that the procedure allowed to quantify PA in Alkanna spp. If the procedure based on 35 specific PA recommended by European regulations had been used, results would have been equal to zero for the four species since none were observed in Alkanna spp. Finally, by combining the RE results with the corresponding dereplication results, a customized correction factor for each extract (ranging from 2.12 to 2.48) was assessed leading to a more accurate estimate of the PA content regardless of the molecular weight of each PA. The present methodology will facilitate PA quantification directly from crude extracts and avoid the underestimation the real PA content due to limited availabilty of authentic reference compounds in botanical extracts used in phytomedicines or food supplements/cosmetics.

Mass Spectrometry-Based Nontargeted and Targeted Analytical Approaches in Fingerprinting and Metabolomics of Food and Agricultural Research

Mass spectrometry (MS)-based techniques have been extensively applied in food and agricultural research. This review aims to address the advances and applications of MS-based analytical strategies in nontargeted and targeted analysis and summarizes the recent publications of MS-based techniques, including flow injection MS fingerprinting, chromatography-tandem MS metabolomics, direct analysis using ambient mass spectrometry, as well as development in MS data deconvolution software packages and databases for metabolomic studies. Various nontargeted and targeted approaches are employed in marker compounds identification, material adulteration detection, and the analysis of specific classes of secondary metabolites. In the newly emerged applications, the recent advances in computer tools for the fast deconvolution of MS data in targeted secondary metabolite analysis are highlighted.

Metabolomic fingerprint of Hamamelis virginiana L. gallotannins by suspect screening analysis with UHPLC-qToF and their semiquantitative evaluation

The evolution of the regulatory framework for medical devices in the EU (Reg 2017/745) has opened the study of complex systems emerging properties. This makes necessary to identify new analytical approaches able of characterizing complex natural substrates as completely as possible. Therefore, omics approaches and advanced analytical methods for the determination of metabolite classes appear to be at the forefront to meet this need. In this perspective, a new approach based on the suspect screening was developed to detect gallotannins. Gallotannins are a class of phenols with a polymeric nature; thus, there are no pure analytical standards available for all possible structures and their quali-quantitative determination in complex natural substrates can be a challenge. A new UHPLC-qToF method was developed and used to create an "in-house tannin database" with a dual purpose: (1) as a classic list of suspects and (2) to identify core fragments common to gallotannins to have another list of putative suspects based on the common fragment. The method was validated. The application of the method to a "system of molecules" extracted from the leaves of Hamamelis virginiana L. (Witch-hazel) allowed to the characterization of a total of 29 phenols by a suspect screening approach. Therefore, 15 gallotannins were putatively annotated while another 3 were confidently identified. All the gallotannins were semiquantified according to external regression curves of gallic acid and hamamelitannin based on core fragments at m/z 125.0244 and m/z 169.0142, the building blocks of the polymers. This new method provides a practical fit-to-purpose approach for the quali-quantitative screening evaluation of gallotannins, useful for creating multivariate control charts applicable in process development of complex natural systems or in quality control. The approach is innovative, and after specific checks, it can in principle be suitable for metabolomic fingerprint analysis of gallotannins among witch-hazel extract (WHE) samples.

High-Performance Liquid Chromatography–Mass Spectrometry Analysis of Glycoalkaloids from Underexploited Solanum Species and Their Acetylcholinesterase Inhibition Activity

Solanum glycoalkaloids are gaining increased scientific attention due to their bioactive potential in the defense of plants against pests and pathogens. The comprehensive glycoalkaloid profiling from the leaves, stems, and roots of seven underexploited Solanum species (S. caripense, S. melanocerasum, S. muricatum, S. nigrum, S. quitoense, S. retroflexum, and S. sisymbriifolium) was conducted using high-performance liquid chromatography–time-of-flight mass spectrometry. A total of 51 glycoalkaloids were shared among the studied Solanum species, with concentrations ranging from 7 to 5.63 × 10⁵ ng g⁻¹. Based on the glycoalkaloid composition, plants were separated into two clusters, Cluster 1 (S. melanocerasum, S. nigrum, and S. retroflexum) and Cluster 2 (S. caripense, S. muricatum, S. quitoense, and S. sisymbriifolium). The inhibition activity of glycoalkaloid extracts on acetylcholinesterase showed a half-maximal inhibitory concentration (IC₅₀), ranging from 0.4 (S. nigrum stems) to 344.9 µg mL⁻¹ (S. sisymbriifolium leaves), that was not directly correlated to the total glycoalkaloid contents. This suggests that the composition of glycoalkaloids in the plant extract, rather than the total concentration, is a driver of biological activity. The study provides a framework for the bioprospecting of underexploited Solanum species for exploring bioactive glycoalkaloids and other compounds with potential pesticidal activities for the development of green bioformulation. This is the first comprehensive report on the glycoalkaloid profiles of S. retroflexum.

Multi-marker scans coupled to high-resolution mass spectrometry strategy for global profiling combined with structure recognition of unknown trace chlorogenic acids in Lonicera Flos

Deep investigation, profiling of chemical diversity of constituent compounds and discovery of novel structures is a great challenge. A novel comprehensive and effective approach to mine trace unknown compounds combined with structure recognition in complex matrix is developed, in order to profiling potential Chlorogenic acids (CGAs) in Lonicera Flos (LFs): using multiple neutral loss/precursor ion (NL/PI) markers scans combined with high resolution mass spectrometry (HRMS). The workflow included (i) Fragmentation rules deduced by Q-orbitrap and selection of multiple NL/PI markers. (ii) Multiple NL/PI marker scans and grouping of peaks that had responses on two or more channels. (iii) Alignment of peaks in Full-MS scan and multiple NL/PI scans. (iv) The precursor ions list was introduced to mine novel CGAs according to simulated molecular formula. (v) Identification and structure recognition with the aid of HRMS. The procedure proved to be valid to screen and identify 51 CGAs from Lonicera Flos (LFs) with 16 categories, especially dihydroxyphenyl and glucoside for the first time. Its application could also be extended for global profiling of other complicated chemical systems, such as Chinese medicinal formulas.

Technical Overview of Orbitrap High Resolution Mass Spectrometry and Its Application to the Detection of Small Molecules in Food (Update Since 2012)

Food safety and quality issues are becoming increasingly important and attract much attention, requiring the development of better analytical platforms. For example, high-resolution (especially Orbitrap) mass spectrometry simultaneously offers versatile functions such as targeted/non-targeted screening while providing qualitative and quantitative information on an almost unlimited number of analytes to facilitate routine analysis and even allows for official surveillance in the food field. This review covers the current state of Orbitrap mass spectrometry (OMS) usage in food analysis based on research reported in 2012-2019, particularly highlighting the technical aspects of OMS application and the achievement of OMS-based screening and quantitative analysis in the food field. The gained insights enhance our understanding of state-of-the-art high-resolution mass spectrometry and highlight the challenges and directions of future research.