Theoretical Elucidation on Activity Differences of Ten Flavonoid Antioxidants

Theoretical methods including structure-activity relationships (SAR) and quantum chemical calculations were used to elucidate the free radical scavenging activity differences of 10 flavonoid antioxidants. SAR could give a qualitative explanation on the antioxidant activity differences. And a further elucidation was performed by a theoretical parameter, the difference of heat of formation between antioxidant and its free radical (deltaHOF), calculated by Austin Model 1 (AM1) method. Besides, deltaHOF showed a linear correlationship with the logarithm of the relative antioxidant efficiency (lgRAE, r = 0.7523), indicating that the theoretical methods were effective to elucidate the differences of antioxidant activity. On the other hand, the ineffectiveness of another theoretical parameter, the highest occupied molecular orbit (HOMO) energy level, was verified further.