Superoxide Scavenging activity was assayed in the xanthine-XO system by measuring the inhibition of reduction of nitro blue tetrazolium (NBT) to from blu formazan which has absorption at 560 nm. O2 production and XO activity were measured as NBT reduction (at 560 nm) and uric production (at 295 nm),respectively. The abilities of the tested compounds to scavenge O2 were compared to those of GSH and vitamin C.