Density Functional Theory Study on Antioxidant Activity of Three Polyphenols

Area of Science:

• Computational Chemistry
• Natural Products Chemistry
• Pharmacology

Background:

• Natural antioxidants, particularly polyphenols, are gaining attention for their health benefits.
• Understanding the antioxidant mechanisms of polyphenols is crucial for developing functional foods.
• Quantum chemistry offers a theoretical framework to investigate molecular properties related to antioxidant activity.

Purpose of the Study:

• To investigate and compare the antioxidant activities of resveratrol, liquiritigenin, and isoliquiritigenin using quantum chemistry.
• To identify the primary active sites responsible for the antioxidant effects of these polyphenols.
• To provide a theoretical basis for the development of polyphenol-rich health foods.

Main Methods:

• Density functional theory (DFT) calculations (B3LYP/6-311G(d,p) and B3LYP/6-311++G(2d,2p)) were employed for molecular optimization and single-point energy calculations.
• Key antioxidant descriptors including bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) were computed in various phase states.
• Frontier molecular orbital analysis and molecular dynamics simulations were performed to explore reaction mechanisms and identify active sites for radical scavenging (·OH and ·OOH).

Main Results:

• The calculated antioxidant activity followed the order: Resveratrol > Isoliquiritigenin > Liquiritigenin.
• The phenolic hydroxyl groups at C4' (Resveratrol), C4' (Isoliquiritigenin), and C4 (Liquiritigenin) were identified as the most probable active sites.
• Antioxidant activity remained consistent across different phase states, though the activity varied among the different phenolic hydroxyl sites within each compound.

Conclusions:

• Quantum chemical calculations provide valuable insights into the antioxidant mechanisms of polyphenols.
• Resveratrol demonstrates superior antioxidant potential compared to liquiritigenin and isoliquiritigenin.
• The identified active sites offer targets for designing more potent polyphenol-based antioxidants for health applications.