Hydrogen bonding interactions between Hibiscetin and ethanol/water: DFT studies on structure and topologies

Abstract

The therapeutic effects of the plant Hibiscus sabdariffa are attributed significantly to the flavonoid Hibiscetin. Water and ethanol are frequently used as solvents in the extraction of flavonoids. Hydrogen bonding interactions are highly significant in the extraction process. Density functional theory (DFT) methods were used in the present investigation to theoretically examine hydrogen bonding interactions between Hibiscetin and ethanol/water. Molecular geometries, interaction energies, topological and charge studies of the complexes were investigated using the 6–311+G(d,p) basis set at the B3LYP-GD3 and M06–2X levels of theory. Eleven Hibiscetin-CH3CH2OH and nine Hibiscetin-H2O stable complexes were obtained after thorough optimization. 8OH and 5′OH positions were found to be the ideal interaction sites. The hydrogen bonds formed by the hydroxyl hydrogen atoms were moderately strong and partially covalent by the QTAIM, NCI, and ELF analyses. The MEP and NBO analyses validated the electron and charge transport from the hydrogen bond donor to the acceptor.