Curcumin, a hydrophobic polyphenol derived from rhizome (turmeric) of the herb Curcuma longa, have been shown to exhibit antioxidant, anticarcinogenic anti-inflammatory, antimicrobial and nephroprotective activities, et al. Among these, its potent antioxidant activity is worthwhile of special attention, because oxidative stress is involved in the pathogenesis of cancer, neurodegenerative diseases, et al. This review focuses on the ways that curcumin exerts its antioxidant activity, including direct chemical reaction with free radicals, chelation with metals ions which results in oxidative stre...