DFT study of glycosyl group reactivity in quercetin derivatives

• Electron donating ability of 3 Quercetin derivatives are analyzed.
• High reactivity of B-ring in Q3G, Q7G and Q3′G is confirmed by BDE and MEP.
• NBO precisely differentiates the weak and strong intramolecular H-bond.
• Q7G donates electron readily than Q3G and Q3′G.

Density functional theory (DFT) is used to compute relevant electronic properties with the purpose of generating precise information which facilitates the best activity given by the positions of glycosyl group attached at all 3 different rings of quercetin such as Q3G (C- ring), Q7G (A-ring) and Q3′G (B-ring). Computed values of the OH BDE, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), Density of states (DOS,PDOS,OPDOS) and electronic properties such as electron affinity (EA), ionization potential (IP), softness (S), hardness (η), electronegativity (χ) and electrophilic index (ω) indicate that the title compounds possess good radical scavenging activity. Charge delocalization and intramolecular hydrogen bonds are characterized using natural bond orbital (NBO) analysis. NBO accurately differentiate the weak and strong intramolecular hydrogen bond of quercetin-O-glycoside compounds. Results available from the computational investigation have proved that A-ring glycoside of quercetin is capable of donating electrons and acts as a good anti-oxidant than B-ring glycoside and C-ring glycoside of quercetin.

The aim of the present investigation is to evaluate the best radical scavenger among Q3G, Q7G and Q3′G flavonoid compounds. Density functional theory is used to compute electronic properties with the purpose of generating accurate information which facilitates better understanding of the anti-oxidant behavior exhibited by the quercetin-O-glycoside flavonoids. To identify the best electron donor among 3 flavonoids the computational studies, OH BDE, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), Density of states (DOS), Natural bond orbital (NBO) and electronic properties such as electron affinity (EA), ionization potential (IP), softness (S), hardness (η), electronegativity (χ) and electrophilicity index (ω) have been initiated.Figure optionsDownload as PowerPoint slide