Density Functional Theory Analysis of Luteolin Molecular Structure and Spectrum.

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Pharmacology

Background:

• Luteolin, a natural flavonoid, possesses known antioxidant and antitumor properties.
• The precise molecular mechanisms linking luteolin's electronic structure to its pharmacological effects remain underexplored.
• Understanding structure-property relationships is crucial for elucidating chemical characteristics and reaction pathways.

Purpose of the Study:

• To analyze the electronic structure parameters of luteolin using density functional theory.
• To reveal the correlation between luteolin's active sites and its biological functions.
• To provide a theoretical basis for luteolin's pharmacological effects and guide drug design.

Main Methods:

• Geometric configuration optimization using the B3LYP-D3-(BJ)/6-311G-(d,p) method.
• Calculation of electronic structure parameters: Frontier Molecular Orbitals (FMOs), electron affinity (EA), ionization potential (IP), density of states (DOS), bond dissociation energy (BDE), proton affinity (PA), molecular surface electrostatic potential (MESP), and vibrational spectra.
• Prediction of ¹H and ¹³C Nuclear Magnetic Resonance (NMR) chemical shifts using gauge-including atomic orbital (GIAO) theory.

Main Results:

• Geometric optimization and spectral analysis confirmed hydrogen bonds and conjugated systems, crucial for antioxidant and antitumor potential via electron delocalization and stability modulation.
• Density of States (DOS) analysis indicated the p-orbital-dominated conjugated system as central to chemical stability and antioxidant activity.
• Calculated parameters (HOMO-LUMO gap: 4.37 eV, BDE: 304.27 kJ/mol, IP: 724.44 kJ/mol) and MESP analysis identified specific hydroxyl and carbonyl groups as key active sites for luteolin's radical scavenging and biological activities.

Conclusions:

• Luteolin's antioxidant and antitumor effects are strongly linked to its electronic structure, particularly its conjugated backbone and intramolecular hydrogen bonds.
• The compound efficiently scavenges free radicals through combined mechanisms (hydrogen atom transfer, sequential proton loss electron transfer, single electron transfer followed by proton transfer).
• The phenolic hydroxyl group on ring B and the carbonyl group on ring C are identified as critical active sites, offering valuable insights for targeted luteolin-based drug development.