Siberian Federal University

The structure-radical scavenging activity relationship for some cinnamic acid derivatives was investigated. The radical scavenging activity (RSA) using modern assays were studied and the effective coefficients for all compounds were calculated. It was founded that hydroxyl group presence is increasing the reduction properties of the cinnamic acid, and the m- substitute presence is decreasing the IC50 value. The most effective antioxidants are o-dihydroxy substituted caffeic and ferulic acids; it could exceed the DPPH RSA of the cinnamic acid in 3.2times, BHA - in 1.6 times. Using quantum-chemistry program some physic-chemical properties like as ionization potential (IP), electron affinity energy and O-H bond dissociation enthalpy, which can be used as an antioxidant activity descriptors were calculated. The not having any O-H group in structure cinnamic acid has the highest value of IP, m-substitution of O-H group in hydroxyl cinnamic acid is decreasing the reduction ability as compared to o-substitution. The highest antioxidant potential of the chlorogenic and ascorbic acids is confirmed by the least IP values. The correlation analysis foe the experimental and theoretical data was searched with the confidence factor value R²=0.5265