METHYLATION EFFECT OF APIGENIN 8-C-GLUCOSIDE TOWARDS ANTIOXIDANT POTENTIAL – A DFT STUDY

The extensive study on O – methylated flavonoids reveals that substitution with methyl group enhances the radical scavenging behavior in certain compounds. Due to potential applications of C-glycosides in metabolic engineering, methylation in these flavonoids needs to be analyzed in both theoretical and experimental levels for their radical scavenging behavior. In this work naturally occurring C- glycosyl flavonoid apigenin 8-C-glucoside (vitexin) is theoretically simulated by substituting the C4′, C5 and C7 hydroxyl positions with methoxy unit and studied with the aid of density functional theory (DFT) for radical scavenging behavior. Structural stability is attained through B3LYP/6-311G(d,p) theory using Gaussian 03 package which provided the stable conformer for the studied compound without imaginary frequency. Structural activity is analyzed with the support of parameters like kinetic energy (temperature independent), HOMO-LUMO, molecular descriptors, Mulliken charge density analysis and compared with vitexin. Combined investigation of the parameters above revealed the superiority of phenyl hydroxyl vitexin over phenyl methoxy vitexin for radical scavenging activity unlike its O methylated flavonoids.