Abstract
Inhibition of free radicals using quercetin, hyperin and rutin is examined to determine their antioxidant effects and the structure–activity relationships of flavonoids. Two species of the free radicals are used, including hydroxyl radical (·OH) and superoxide anion radical (O2 −·). Density functional theory calculations under the level of B3LYP/6-311G (d) have been utilized to explore the structure, molecular properties and antioxidant abilities of the three flavonoids. Bond dissociation enthalpy (BDE) and frontier molecular orbital energy gap are investigated. They are compared with the experiment results assayed by the spectrophotometric. All of the flavonoids show a high activity on inhibiting ·OH and O2 −· radicals. Scavenging activity determined by half maximal inhibitory concentration (IC50) values of the three flavonoids decreases in the order: quercetin > hyperin > rutin. The calculations show that quercetin owns the lowest BDE values, which agree well with the experimental results of antioxidant activity determined by IC50 values.
Highlights
Free radicals such as hydroxyl radical (·OH) and superoxide anion radical (O2−·) are toxic compounds produced by the oxidative reaction
A slight modification is made according to Ref. [14]: 2 mmol/L FeSO4 5 mL and 6 mmol/L H2O2 5 mL are put into 25-mL colorimetric tubes, the mixture is shaken well and 6 mmol/L salicylic acid is added to the mark
The antioxidant activities of the three flavonoids are compared with standard antioxidant vitamin C (VC)
Summary
Free radicals such as hydroxyl radical (·OH) and superoxide anion radical (O2−·) are toxic compounds produced by the oxidative reaction. They have a high activity and can slowly cause severe damage to the cells [1]. Flavonoids typically show strong antioxidant activity by scavenging free radicals [2]. The radical scavenging properties of flavonoids are based on the phenol hydroxyl and the possibility of stabilization of the resulting phenoxyl radicals through hydrogen bonding or extended electron delocalization [4]. A number of studies have established the hierarchy of flavonoids in terms of their antioxidant activities and the corresponding structure–activity relationship (SAR) in vitro [5, 6]. The existing data are principally focused on the effects of the position and number of hydroxyl group in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
