Comparative potencies of nutraceuticals in chemically induced skin tumor prevention.

Four nutraceuticals, sugar beet roots, cucumber fruits, New Zealand spinach leaves, and turmeric rhizomes, were evaluated for their comparative effectiveness against dimethylbenz[a]anthracene (DMBA)-initiated and croton oil-promoted skin tumors. Three different protocols were used. The most effective protocol (Protocol 2) is the topical application of the nutraceuticals 1 h before croton oil. There was a decrease in the percent skin tumor incidence, a decrease in multiplicity of skin tumors, and a later onset of skin tumors compared with the positive control for all the nutraceuticals tested, with turmeric being the most potent, as evidenced by 30% skin tumor incidence, 87.2% decrease in skin tumors, and a 5-wk delay in skin tumor formation compared with the positive control. Topical application of the nutraceuticals daily for 5 days before DMBA and 1 h before croton oil (Protocol 1) and immediately after croton oil (Protocol 3) did not have an additional protective effect against skin tumors compared with Protocol 2. Kruskal-Wallis analysis of variance by ranks showed that Protocol 2 is the most effective, with the treatment groups belonging to different populations at the 0.05 level of significance compared with alpha = 0.20 for Protocols 1 and 3. Turmeric is the most potent nutraceutical, because the average number of tumors formed after application of tumeric is statistically different from the positive control at alpha = 0.01.