In Silico Studies on Sennidines-Natural Dianthrones from Senna.

Area of Science:

• Computational chemistry
• Pharmacological research
• Natural product analysis

Background:

• In silico methods, particularly quantum-chemical approaches, are increasingly vital for accurate biological system research.
• These methods enhance the understanding of molecular structure, properties, and interactions, especially for pharmacologically significant compounds.

Purpose of the Study:

• To determine the spatial structure and intramolecular interactions of sennidines, natural pharmaceutical compounds from *Senna* species.
• To provide theoretical data that can aid in the analysis of experimental samples.

Main Methods:

• Quantum-chemical calculations were performed in both gas-phase and solvent models.
• Analyses included Quantum Theory of Atoms in Molecules (QTAIM) and Non-covalent Interactions (NCI).
• Comparison with existing experimental data was conducted.

Main Results:

• Sennidines exhibit the ability to form multiple conformers.
• Numerous intramolecular interactions were identified within the sennidin structure.
• The lowest energy optimized structure suggests a gauche conformation for sennidin in plant material.
• An elongated C-C bond with reduced Bond Dissociation Energy (BDE) indicates potential breakdown into monoanthrones.

Conclusions:

• The study predicts the predominant gauche conformation of sennidin in natural sources.
• Identified intramolecular interactions and bond characteristics offer insights into sennidin's stability and degradation pathways.
• Generated theoretical spectra (vibrational, electron excitation) can serve as a reference for experimental analysis.