Ramesh Kheirabadi - Department of chemistry, Mashhad Branch, Islamic Azad university, Mashhad, Iran
Mohammad Momen Heravi
Mohammad reza Bozorgmehr

Reactions of free radicals and reactive oxygen species (ROS) with biological molecules in vivo play an important physiological role in manydiseases. 2,2-diphenyl-1-picrylhydrazyl (DPPH) isa stable free radical and often used as substrate to evaluate the antioxidant capacity of an antioxidant.This study was undertaken to investigate the free radical-scavenging and antioxidant activities of Taxol as an anti cancer drug, Vitamin C as anantioxidant and mixture of them. UV-Vis spectrometry method was used to evaluate the ability mixture of Taxol, Vitamin C to scavengeDPPH radical. The kinetic parameters such as rateconstant , activation energy and thermodaynamic parameters such as anthalpy and anthropy inexperimental conditions were calculated. The rateconstants of the ( H ) atom abstraction by DPPH, in the presence mixture of Taxol , Vitamin C wasobtained 0.0918 s-1,under pseudo-first-order conditions at 25 oC . Anthalpy , anthropy for mixture of them were obtained -6.242 Kcal.mol-1 -83.956 cal K-1 mol -1 respectively