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Mass Spectrometry and NMR Profiling: Strategies for Natural Products Characterization

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 9595

Special Issue Editors


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Guest Editor
Department of Chemical Sciences, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
Interests: mass spectrometry; NMR; chromatographic separation; natural products chemistry; proteomics; food analysis; organic chemistry
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Guest Editor
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies—DiSTABiF, University of Campania “Luigi Vanvitelli”, Via Vivaldi 43, 81100 Caserta, Italy
Interests: natural product chemistry; metabolomics; NMR; isolation and structural elucidation of metabolites; allelopathy; bioactive compounds
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Universidad del Valle, Cali, Colombia
Interests: NMR; complex mixture analysis; metabolomics; cheminformatics

Special Issue Information

Dear Colleagues,

In recent years, natural products (NPs) have been the focus of an increasing number of research studies. The broad structural diversity of NPs attracts the attention of chemists, cell biologists, chemical engineers, analytical chemists and microbiologists, stimulated by the need for new therapeutics to address existing and emerging infectious diseases.

The potential use of a natural extract or an isolated compound is closely related to their composition determination and structure, respectively. The analytical tools which contribute to gain the molecular characterization of mixtures or isolated NPs are not numerous and are dominated by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. To unravel the complexity of NPs and identify the entities of interest, they are usually coupled with high-resolution separation techniques (i.e. HPLC or capillary electrophoresis) and with cheminformatics approach to simplify the results and interpret them. 

This Special Issue of Molecules is dedicated to original research and review articles that cover the latest findings on NPs characterization.

Dr. Vera Muccilli
Dr. Monica Scognamiglio
Dr. Julien Wist
Guest Editors

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Keywords

  • Mass spectrometry
  • Nuclear magnetic resonance spectroscopy
  • Molecular structure
  • Natural Products
  • Structural elucidation
  • Extract dereplication

Published Papers (4 papers)

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Research

17 pages, 11208 KiB  
Article
Investigation of the Variability of Alkaloids in Buxus sempervirens L. Using Multivariate Data Analysis of LC/MS Profiles
by Lara U. Szabó and Thomas J. Schmidt
Molecules 2022, 27(1), 82; https://doi.org/10.3390/molecules27010082 - 23 Dec 2021
Cited by 1 | Viewed by 2333
Abstract
Buxus sempervirens L. is a common ornamental plant in southern and central Europe, and has been used ethopharmacologically against a wide variety of diseases due to it containing nor-triterpene alkaloids of the nor-cycloartane type. Recently, we demonstrated the interesting antiprotozoal potential [...] Read more.
Buxus sempervirens L. is a common ornamental plant in southern and central Europe, and has been used ethopharmacologically against a wide variety of diseases due to it containing nor-triterpene alkaloids of the nor-cycloartane type. Recently, we demonstrated the interesting antiprotozoal potential of some of these compounds. To characterize the temporal variability in the alkaloid profile of two different varieties and their leaves and twigs, 30 different extracts of B. sempervirens were evaluated by Ultra High Performance Liquid Chromatography/positive Mode-Electrospray Ionization Quadrupole Time-of-Flight-Tandem Mass Spectrometry (UHPLC/+ESI-QqTOF-MS/MS). The analytical profiles were thoroughly investigated by various methods of multivariate data analysis (MVDA). A principal component analysis (PCA) model elucidates the seasonal variation in the phytochemical composition of B. sempervirens var. arborescens and suffruticosa along with differences between the varieties. Analysis of a volcano plot illustrated the differences between the two organs, the leaf and twig. Eighteen compounds were highlighted by the models as constituents of the plant characteristic for a season, variety or organ. These compounds were dereplicated based on their chromatographic and +ESI-QqTOF-MS and –MS/MS data. In addition, mass spectral fragmentation pathways for already known alkaloids as well as new natural products could be postulated for the first time. In conclusion, the MVDA models give detailed information on the temporal variability in the alkaloid profile of two different varieties and their organs (leaf vs. twig) of B. sempervirens. Thus, the results of this study allow, e.g., the identification of characteristic compounds for the different varieties, plant organs, seasons, and the optimal harvesting time for the isolation of particular Buxus-alkaloids of interest for subsequent studies. Full article
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12 pages, 2430 KiB  
Article
1H NMR Combined with Multivariate Statistics for Discrimination of Female and Male Flower Buds of Populus tomentosa
by Bo Xu, Cui Wu, Zhuojun Li, Pingping Song and Zhimao Chao
Molecules 2021, 26(21), 6458; https://doi.org/10.3390/molecules26216458 - 26 Oct 2021
Cited by 4 | Viewed by 1754
Abstract
1H Nuclear Magnetic Resonance (1H NMR) combined with multivariate statistics was adopted to discriminate female and male flower buds of Populus tomentosa in the study. Samples of 11 female and 16 male flower buds of P. tomentosa were collected in [...] Read more.
1H Nuclear Magnetic Resonance (1H NMR) combined with multivariate statistics was adopted to discriminate female and male flower buds of Populus tomentosa in the study. Samples of 11 female and 16 male flower buds of P. tomentosa were collected in Beijing, China. 1H NMR spectra were acquired on a 400 MHz spectrometer. In total, 30 chemical compounds were identified with standards and literature according to chemical shifts, peak areas, and multiplicity. Principal component analysis (PCA), hierarchical clustering analysis (HCA), and supervised orthogonal partial least squares-discriminant analysis (OPLS-DA) were applied to discriminate female and male flower buds. An apparent grouping trend (R2X, 0.809; Q2, 0.903) between female and male groups was exhibited with PCA and HCA. The two groups were also well discriminated with OPLS-DA (R2X, 0.808; R2Y, 0.976; Q2, 0.960). Combined with variable importance in projection (VIP) > 1.0 and p < 0.05 of OPLS-DA, it was found that the content of daucosterol, β-sitosterol, ursolic acid, and betulonic acid in male group was higher than that in female, which should be the key differences of chemical constituents in female and male flower buds of P. tomentosa. The study demonstrated that 1H NMR combined with multivariate statistics could be used to discriminate female and male plants and clarify differences, which provided a novel method to identify the gender of dioecious plants. Full article
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13 pages, 3062 KiB  
Article
Identification of Antiprotozoal Compounds from Buxus sempervirens L. by PLS-Prediction
by Lara U. Szabó, Marcel Kaiser, Pascal Mäser and Thomas J. Schmidt
Molecules 2021, 26(20), 6181; https://doi.org/10.3390/molecules26206181 - 13 Oct 2021
Cited by 2 | Viewed by 1672
Abstract
Various nor-triterpene alkaloids of Buxus (B.) sempervirens L. have shown remarkable in vitro activity against the causative agents of tropical malaria and East African sleeping sickness. To identify further antiprotozoal compounds of this plant, 20 different fractions of B. [...] Read more.
Various nor-triterpene alkaloids of Buxus (B.) sempervirens L. have shown remarkable in vitro activity against the causative agents of tropical malaria and East African sleeping sickness. To identify further antiprotozoal compounds of this plant, 20 different fractions of B. sempervirens L., exhibiting a wide range of in vitro bioactivity, were analyzed by UHPLC/+ESI-QqTOF-MS/MS. The analytical profiles were investigated by partial least squares regression (PLS) for correlations between the intensity of LC/MS signals, bioactivity and cytotoxicity. The resulting models highlighted several compounds as mainly responsible for the antiprotozoal activity and thus, worthwhile for subsequent isolation. These compounds were dereplicated based on their mass spectra in comparison with isolated compounds recently reported by us and with literature data. Moreover, an estimation of the cytotoxicity of the highlighted compounds was derived from an additional PLS model in order to identify plant constituents with strong selectivity. In conclusion, high levels of antitrypanosomal and antiplasmodial activity were predicted for eight and four compounds, respectively. These include three hitherto unknown constituents of B. sempervirens L., presumably new natural products. Full article
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20 pages, 1840 KiB  
Article
Mass Spectrometry and 1H-NMR Study of Schinopsis lorentzii (Quebracho) Tannins as a Source of Hypoglycemic and Antioxidant Principles
by Nunzio Cardullo, Vera Muccilli, Vincenzo Cunsolo and Corrado Tringali
Molecules 2020, 25(14), 3257; https://doi.org/10.3390/molecules25143257 - 17 Jul 2020
Cited by 16 | Viewed by 3074
Abstract
The ethyl acetate extract of the commercial tannin Tan’Activ QS-SOL (from Schinopsis lorentzii wood), employed for the production of red wine, was subjected to chromatography on Sephadex LH-20, providing nine fractions (A-1–A-9), which were estimated for total phenols content (GAE), antioxidant activity (DPPH, [...] Read more.
The ethyl acetate extract of the commercial tannin Tan’Activ QS-SOL (from Schinopsis lorentzii wood), employed for the production of red wine, was subjected to chromatography on Sephadex LH-20, providing nine fractions (A-1–A-9), which were estimated for total phenols content (GAE), antioxidant activity (DPPH, ORAC), and hypoglycemic activity (α-glucosidase and α-amylase inhibition). All the fractions were analyzed by means of HPLC/ESI-MS/MS and 1H-NMR to identify the principal active constituents. Fractions A-1 and A-3 showed the highest antioxidant activity and gallic acid (1), pyrogallol (3), eriodictyol (6), catechin (12), and taxifolin (30) were identified as the major constituents. The highest α-glucosidase and α-amylase inhibitory activity was observed in fractions A-7–A-9 containing condensed (9′, 15, 18, 19, 23, and 27) hydrolysable tannins (13 and 32) as well as esters of quinic acid with different units of gallic acid (5, 11, 11′, 14, and 22). This last class of gallic acid esters are here reported for the first time as α-glucosidase and α-amylase inhibitors. Full article
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