The numerous beneficial effects attributed to turmeric stem in large measure from the antioxidant properties of curcumin. Antioxidants neutralize free radicals, which are highly unstable molecules that can damage cellular structures through abnormal oxidative reactions. Curcumin is a potent “scavenger” of the superoxide radical, a free radical that initiates potentially harmful oxidative processes such as lipid peroxidation.5 Through this activity, curcumin has been shown to protect skin cells from the injurious effect of nitroblue tetrazolium, a toxin that generates superoxide radicals. Curcumin also increases survival of cells exposed in vitro to the enzyme hypoxanthine/xanthine oxidase, which stimulates superoxide and hydrogen peroxide production. Curcumin is not toxic to cells, even at high concentrations. “Pure” curcumin (see first paragraph under “Ingredients” above) was shown to be less protective that a mixture of curcuminoids, indicating a possible synergism among the curcuminoids.6 Because free radicals are involved in aging and exert harmful effects on skin, these results suggest curcumin may help slow skin aging.

Curcumin demonstrates several other in vitro effects linked to free radical scavenging. Curcumin scavenges nitric oxide, a compound associated with the body’s inflammatory response.7 Pure curcumin and turmeric extracts protect red blood cells from lipid peroxidation induced by hydrogen peroxide.8 Curcumin has been shown to protect DNA from oxidative damage, inhibit binding of toxic metabolites to DNA, and reduce DNA mutations in the Ames’ test.9 Although additional studies suggest an anticarcinogenic effect of curcumin, through protection of DNA,10 one in vitro study found that curcumin induced DNA damage in human gastric mucosal cells.11 It is speculated that curcumin may act as a pro-oxidant in the presence of transition metal ions such as copper and iron. (This is true for other antioxidants, including vitamin C.) Curcumin also demonstrates in vitro inhibition of COX-I and COX-II enzymes, which are involved in the inflammatory reaction.12 Together these results strongly suggest that curcumin is a potent bioprotectant with a potentially wide range of therapeutic applications.