Laser flash photolysis study on antioxidant properties of hydroxycinnamic acid derivatives.

The antioxidant properties of hydroxycinnamic acid derivatives (HCA) were studied by laser flash photolysis. The transient species with maximum absorption at 360 nm were assigned to the phenoxyl radical of HCA. The SO (4) (.-) induced oxidation of HCA was also investigated. It was shown that the interaction of SO (4) (.-) with HCA resulted in the formation of HCA phenoxyl radicals with rate constants of 2.0-3.9 x 10(9 )M(-1) s(-1). The reactions of HCA with triplet state of benzophenone were analyzed and quenching rate constants of 4.3-7.8 x 10(9 )M(-1) s(-1) were determined.