Abstract
The flavonolignans (silybin and analogues) are important natural compounds with multiple biological activities operating at various cell levels. Many of these effects are connected with their radical scavenging activities. In the present study, freeβradical scavenging and antioxidant activities of four natural flavonoids, namely silybin, naringenin, naringin, and hesperetin, have been studied using nanosecond pulse radiolysis techniques. The kinetics and mechanisms of the reactions of silybin and analogues with various oxidizing radicals (such as ^β’^OH,N~3~^β’^, CCl~3~OO^β’^, SO~4~^β’β^) have been investigated. Furthermore, the transient species has been assigned and radical scavenging rate constants have also been measured. Moreover, the structureβactivity relationships between chemical structures of the flavonoids and their radical scavenging activities are further analayzed by theoretical calculation. Combined our previous observation of the fast reparation of DNA damage and efficient DNA protection against radiation damage in vitro, it can be confirmed that test flavonoids are promising molecules to be used for their potential antioxidant properties. Β© 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 590β597, 2011