Density Functional Theory Calculation On Scutellaria Baicalensis Georgi's Flavonoids Eliminating Free Radicals

As important food additive, antioxidant is essential to human health. It can eliminate free radicals bytransmitting electronics. Today, food security has been paid more and more attention, seeking a safe,reliable antioxidant appears particularly important. Flavone compounds have excellent free radicalscavenging effect, they through the hydroxyl hydrogen atom to exert an antioxidant effect. This paperstudies on several flavonoids in Scutellaria Baicalensis Georgi. They are excellent antioxidants, which areantioxidant, free radical scavenging, antimicrobial, antitumor effect, safety, harmless, high efficiency.Quantum chemistry is based on the quantum mechanics, using the theory and method to solvechemistry problems. In quantum chemistry, Density Functional Theory is the effective tool to solvedifficult problems in electronic structure theory. In this paper, using Gaussian software to build suitablemolecular models, and to get the energies and structure index. Analysizing the compound's electronicstructure, molecular structure parameters and spectral properties, to explore their activity. DFT has beenwidely used in molecular structure and properties, spectroscopy, thermal chemistry, transition state anddeveloped toward material science, life science, drug design and other areas.Baicalin, Baicalein, Wogonoside and Wogonin, which are four main components of Scutellariabaicalensis Georgi, were calculated using DFT B3LYP method with6-311G(d) basis set. Their activitieswere analyzed based on bond length, natural population, BDE, the frontier orbitals and hydrophilicproperty. The result showed that the bond length of phenolic hydroxyl at C5of the Baicalin was the longestone. The hydrogen atom of phenolic hydroxyl at C5possessed the largest positive charge in all the fourmolecules. The charge on the hydrogen atom decreased along the series: Baicalin＞Baicalein＞Wogonin＞Wogonoside. The BDE of phenolic hydroxyl at C5showed the activity series: Baicalin＞Baicalein＞Wogonin＞Wogonoside. The energy gap between HOMO and LUMO increased along the series: Baicalin＜Wogonoside＜Baicalein＜Wogonin. But the hydrophilic property showed that the Glucuronideincreased the solubility of Baicalin and Baicalein greatly. All the parameters obtained showed that Baicalinhas the highest activity in the four flavonoids. The theoretical result is consistent with the activity order inreported literatures.As the most content of Scutellaria baicalensis Georgi, Baicalin has high activity, so discussing thereaction mechanism of eliminating free radical has a certain significance. Compared the IR spectrum ofBaicalin obtained by using DFT method with standard IR spectrum, you can clearly find that the optimizedstructure is reasonable. Gaussian is good at dealing with reaction mechanism. When C6phenolic hydroxyl on Baicalin scavenging·OH and·O₂^-,the computed result showed the activation energy was113.2kJ·mol-1and the ΔH was-1053kJ·mol^-1.Both of Oroxylin-A and Wogonin, which are isomers, have the effect of antibacterium, antivirus andantitumor. They were calculated using DFT method to provide theoretical foundation for alternativemedicines. To analyze the two molecules' HOMO, their reduction mainly focused on A and C two ringsand phenolic hydroxyl. But their antioxidant active sites on different phenolic hydroxyl. Oroxylin-A'sactive site is on C5phenolic hydroxyl and Wogonin's active site is on C7. As the result of Oroxylin-A andWogonin have different active sites, two kinds of compounds as alternative medicine ideas still needfurther research.Scutellarin is extract of Scutellaria baicalensis Georgi and the main flavonoid of Erigeron breviscapus,which has the C4' phenolic hydroxyl. Scutellarin had wide physiological activity. In this work, Scutellarinwas calculated using the Density Functional Theory(DFT) B3LYP method with6-311G(d) basis set. Themolecular structure, dipole moment, hydrophobic parameter, infrared spectroscopy, phenolic hydroxylbonds dissociation enthalpy, spin density distribution and the frontier orbitals were analyzed to explain itsactivity. The result showed that Scutellarin's antioxidant effect was reflected on its phenolic htdroxyls. TheC6phenolic htdroxyl on the A ring has the highest active, C4' on the B ring was second and C5on the Aring was at last. Scutellarin may have good absorption effect in the polar environment. The result providestheoretical guidance for using Scutellarin effectively.