A theoretical study on the hydrogen-bonding interactions between flavonoids and ethanol/water

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Natural Product Chemistry

Background:

• Ethanol and water are primary solvents for extracting flavonoids from propolis.
• Understanding solvent-flavonoid interactions is crucial for optimizing extraction processes.
• The nature and strength of hydrogen bonding between flavonoids and these solvents are not fully elucidated.

Purpose of the Study:

• To investigate the existence and characteristics of hydrogen-bonding interactions between flavonoids and ethanol/water.
• To determine the preferred sites and relative strengths of these interactions.
• To provide theoretical insights into flavonoid-solvent complexation using computational methods.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• B3LYP/M062X level of theory with the 6-31++G(d,p) basis set was used.
• Molecular geometries, binding energies, charge transfers, and topological analyses were performed for chrysin-water, chrysin-ethanol, galangin-water, and galangin-ethanol complexes.

Main Results:

• Multiple optimized hydrogen-bond geometries were identified for both chrysin and galangin with water and ethanol.
• Flavonoids form strong hydrogen bonds with hydroxyl, carbonyl, and ether groups, and weaker bonds with aromatic hydrogens.
• Chrysin and galangin generally exhibit stronger hydrogen bonding with water than with ethanol, with charge transfer occurring from flavonoids to solvents.

Conclusions:

• Hydrogen bonding between flavonoids (chrysin, galangin) and ethanol/water is confirmed and characterized computationally.
• Specific sites like hydroxyl, carbonyl, and ether groups are preferred for hydrogen bonding.
• The findings contribute to understanding the fundamental interactions governing flavonoid extraction and solvation.