Chlorophylls, chlorins, and other porphyrins have been used clinically for many years, including photodynamic therapy of tumors. More recently, the cancer chemopreventive properties of chlorophylls have come to be recognized. Chlorophylls exhibit anti-mutagenic activity in short-term genotoxicity assays, and protect against various intermediate biomarkers of cancer in vivo. The anticarcinogenic activity of sodium-copper chlorophyllin (CHL), a clinically-used water soluble salt of chlorophyll, has been studied in several species. Collectively, the results from these studies support a chemopreventive role for CHL against aromatic carcinogens (aflatoxins, polycyclic aromatic hydrocarbons, heterocyclic amines) in various target organs of rats, mice, and rainbow trout. In vivo mechanism studies indicate that inhibition is most effective when CHL is administered simultaneously with the carcinogen, thereby allowing direct interaction (molecular complex formation) between CHL and the carcinogen. Studies of post-initiation treatment with CHL have provided conflicting results, with evidence for inhibition or promotion of carcinogenesis. These findings are discussed in terms of the inhibitory and promotional mechanisms of CHL, the relevance of such mechanisms to natural chlorophylls present in the diet, and the current use of CHL as a health supplement.

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