Inhibition of nitrite induced oxidation of hemoglobin by curcuminoids.

Curcumin, demethoxy curcumin, bis demethoxy curcumin and diacetyl curcumin inhibited nitrite induced oxidation of hemoglobin in both erythrocytes and purified human hemoglobin. The activities of all the compounds except diacetyl curcumin were similar suggesting that the methoxy substituents have very little role in this biological activity. Acetylation of phenolic groups resulted in significant reduction of activity.