Abstract
Simple SummaryThe study determines the spatial structure and intramolecular interactions of sennidines—natural pharmaceutical substances present in Senna species. The calculations predict many sennidin conformers with similar energy but the gauche conformation will be present in the plant material. The lowest energy structure that is most likely to be found in plant material is characterized by the presence of OHO hydrogen bonds formed by hydroxyl groups and carbonyl oxygen. The sanidin molecule can be easily breakdown into monoanthrones because of elongation of the single C-C bond linking the anthrone moieties and reduced bond dissociation energy. The work contains data on theoretical, vibrational and electron excitation spectra, which can be used in the analysis of experimental samples.The rapid development of technology allows for more accurate research of biological systems with the use of in silico methods. One of the tools is the quantum-chemical method used for determining the structure, properties and interactions of molecules of great pharmacological importance. The accuracy of theoretical models is increasing and can be a real help in biology, chemistry and pharmacy. The aim of the study is to determine the spatial structure and intramolecular interactions of sennidines—natural pharmaceutical substances present in Senna species. Calculations carried out in the gas-phase and in the solvent model, compared with the available experimental data indicate the possibility of sennidines to form conformers. QTAIM and NCI analysis suggests the presence of many intramolecular interactions in the sennidin structure. Taking into account the lowest energy optimized structure, it can be predicted that the sennidin in the gauche conformation will be present in the plant material. The single C-C bond connecting the anthrone moieties is elongated and its reduced Bond Dissociation Energy (BDE) could be the cause of an easy breakdown of the sennidin molecule into monoanthrones. This work contains data on theoretical, vibrational and electron excitation spectra, which can be used in the analysis of experimental samples.
Highlights
Sennidines belong to a group of compounds composed of double-anthrone moiety
The common part of all of the sennidines is a double-anthrone moiety connected by a single C-C bond
Conformational analysis and the optimization of the sennidin structures was performed by means of the Gaussian16 software [30]
Summary
Sennidines belong to a group of compounds composed of double-anthrone moiety. There are four sennidin structures shown in Scheme 1. The common part of all of the sennidines is a double-anthrone moiety connected by a single C-C bond. Two specific regions can be distinguished in the sennidin molecule. The “peri” region, which includes two hydroxyl groups directed to carbonyl oxygen, and the “bay” region, which is located in the empty space between two anthron moieties. There are COOH or CH2OH groups in the “bay” region, depending on the sennidin type. The structure of sennidin is characterized by a number of substituents. The sennidin structure is characterized by the rotation of the anthron moieties. Substitution at the “bay” region of the molecule with a COOH or CH2OH group produces four sennidin
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