Three natural curcuminoids (curcumin (CAS 458-37-7), demethoxycurcumin
, bisdemethoxycurcumin) and acetylcurcumin were compared for their abi
lity to scavenge superoxide radicals and to interact with 1,1-diphenyl
-2-picryl-hydrazyl (DPPH) stable free radicals. The results showed tha
t curcumin is the most potent scavenger of superoxide radicals followe
d by demethoxycurcumin and bisdemethoxycurcumin. Acetylcurcumin was in
active. Interaction with DPPH showed a similar activity profile. The s
tudy indicates that the phenolic group is essential for the free radic
al scavenging activity and presence of methoxy group further increases
the activity.