Curcuminoids, the main yellow pigments in
Curcuma longa (turmeric), have been used widely
and for a long time in the treatment of sprain
and inflammation in indigenous medicine.
Curcumin is the main component of turmeric,
and two minor components are also present as
the curcuminoids. Curcuminoids possess antioxidant activity, and also are responsible for the
yellow color of curry. Curcumin was reported
to act as a strong inhibitor of tumor promotion,
and this effect roughly parallels the relative
antioxidant activity. Recently, we reported on
the preventive effect of curcumin on radiationinduced tumor initiation in rat mammary
glands. We have also succeeded in obtaining a
strong lipid-soluble antioxidant, tetrahydrocurcumin

(THC), by hydrogenation using Pd-C (or
Raney-nickel) as the catalyst. THC was found
to be produced from curcumin during absorption
from the intestines, and a more potent antioxidant
than curcumin. Recently, we found that THC
is a more promising chemopreventive agent than
curcumin in the 1,2-dimethyl-hydrazine (DMH)
induced mouse colon carcinogenesis model. We
have also found that THC induces antioxidative
enzymes such as glutathione peroxidase,
glutathione S-transferase and NADPH: quinone
reductase, as well as or better than curcumin
and scavenged Fe- NTA-induced free radicals
in vitro better than curcumin. These results
suggest that curcumin is converted to THC in
vivo and that THC is a more promising
chemopreventive agent.