A density functional theory study on the hydrogen bonding interactions between luteolin and ethanol.

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Natural Products Chemistry

Background:

• Ethanol is a common solvent for flavonoid extraction from propolis.
• Hydrogen bonding significantly influences liquid system properties.
• Flavonoids are important natural compounds with diverse biological activities.

Purpose of the Study:

• To investigate the hydrogen bonding interactions between a representative flavonoid, luteolin, and ethanol.
• To understand the nature and strength of these interactions at a molecular level.

Main Methods:

• Density Functional Theory (DFT) was employed for theoretical calculations.
• Nine optimized geometries of the luteolin-ethanol complex were determined.
• Analysis of binding distances, bond lengths, vibrational frequencies, and electron density changes was performed.

Main Results:

• Ethanol forms hydrogen bonds with most atoms in luteolin, particularly with the hydroxyl groups.
• All identified hydrogen bonds are closed-shell interactions.
• The strongest hydrogen bond involves O3'-H3'···O, while the weakest involves C3-H3···O.
• Interactions vary in strength, with some being medium and covalent dominant, and others weak and electrostatic dominant.

Conclusions:

• The study elucidates the specific hydrogen bonding patterns between luteolin and ethanol.
• Understanding these interactions is crucial for optimizing flavonoid extraction processes.
• DFT calculations provide valuable insights into molecular complex formation.