Effect of spice principles on scavenging of superoxide anion has been investigated. The superoxide anions, as measured by nitrobluetetrazolium (NBT) reduction in xanthine-xanthine oxidase system, were inhibited by superoxide dismutase, spice principles eugenol (cloves) and cuminaldehyde (cumin), antioxidants, butylated hydroxy toluene and butylated hydroxyanisole in a dose-dependent manner. The K(i) values for the inhibition of NBT reduction by eugenol and cuminaldehyde were 64 microM and 120 microM respectively. Zingerone (ginger) and linalool (coriander) inhibited NBT reduction to a maximum of 23 and 28% respectively. However, piperine (black pepper) and turmeric extracts (aqueous and acid) failed to scavenge superoxide anions.