Department of Chemistry , Mashhad Branch , Islamic Azad university, Mashhad, Iran
Young Researchers Club, Mashhad Branch, Islamic Azad University, Mashhad, Iran
Extracts of Cotoneaster medicus, Glycyrrhiza glabra, as endemic plants of Iran, along with mixture of them were investigated for their antioxidant activities using 2, 2- diphenyl-1-picrylhidrazyl (DPPH) reagent. UV-Vis spectrophotometry method was used to evaluate the ability of Cotoneaster and Glycyrrhiza glabra antioxidant to scavenge DPPH radical. The kinetic parameters such as rate constant and activation energy in experimental conditions were calculated. The rate constants of the H atom abstraction by DPPH (k1), in the presence of C. medicus and G. glabra antioxidant were obtained under pseudo-first-order conditions at different temperatures. The order in DPPH radical-scavenging was: mixture of C. medicus and G. glabra > C. medicus > G.Â glabra plants. The numerical values of activation energy were found to be 45.84 kJ.mol-1for G. glabra and 62.02kJ.mol-1 for C. medicus.