Editorial: Insights in structural and stereochemical analysis: 2022

Abstract

With four articles, including one perspective, two reviews, and one original research article, the Research Topic Insights in Structural and Stereochemical Analysis: 2022 covers the state-of-the-art research being conducted in the analysis of the structure and 3D arrangements of natural product (NP) molecules. In the perspective article by Lopes and da Silva, mass spectrometry and some advanced landmarks are highlighted in respect to the main challenges and impacts of the chemical characterization of complex molecular structures. In this respect, the complexity of data analysis is discussed as one of the main limitations for time-limited tasks. Moreover, the observed expansion in the mass spectral database is not sufficient for the necessary data interpretation. As emphasized by the authors, the estimated number of spectra for ESI-MS/ MS in the public domain is in the order of 60,000 molecules, which is far below the chemical space, and “traditionally, most spectrometry techniques rely on database matching of previously characterized signals.” Meanwhile, the importance of the recently created large public databases is acknowledged as a means of characterizing large datasets acquired in complex samples such as NP extracts. Machine learning (ML)-based methods are also examined regarding their contribution to the structural prediction of classes of molecules that are poorly represented in spectral libraries. The imaging of small molecules by MALDI-MS grants spatial mapping of in situ NPs, allowing a better understanding of their function and distribution. As technological advances in terms of equipment, images and MS/MS data can be simultaneously generated, allowing the direct annotation of molecules. Additionally, the introduction of a third dimension by ionic mobility reveals the possibility of single-cell analysis by spatial resolution. This perspective article by Lopes and da Silva shines light on these significant issues and all the opportunities ahead of us in NP research. The original article of this Research Topic by Queiroz et al. is about the chemical profile of organic apolar and polar extracts from leaves and stems of Alzatea verticillata Ruiz & Pav. (Alzateaceae). By semipreparative LC, twelve compounds were isolated in a milligram scale, of which three were unknown. The structure elucidation of the isolated compounds was carried out based on NMR and HRMS analyses. The previously undescribed compounds included a dimeric lactone, dimethyl anemonin, and two unusual dimeric diphenyl cyclobutane dicarboxylic acids (β-truxinic derivatives). The X-ray crystallography of the new dimeric lactone revealed it as an (S,S), (R,R) racemate. This article provides a biogenetic proposal that is in line with the obtained racemate. Additionally, non-target LC-HRMS data OPEN ACCESS