Organosulfur compounds and possible mechanism of garlic in cancer.

Garlic (Allium sativum), a member of the family Liliaceae, contains an abundance of chemical compounds that have been shown to possess beneficial effects to protect against several diseases, including cancer. Evidence supports the protective effects of garlic in stomach, colorectal, breast cancer in humans. The protective effects appear to be related to the presence of organosulfur compounds, predominantly allyl derivatives, which also have been shown to inhibit carcinogenesis in forestomach, esophagus, colon, mammary gland and lung of experimental animals. The exact mechanisms of the cancer-preventive effects are not clear, although several hypotheses have been proposed. Organosulfur compounds modulate the activity of several metabolizing enzymes that activate (cytochrome P450s) or detoxify (glutathione S-transferases) carcinogens and inhibit the formation of DNA adducts in several target tissues. Antiproliferative activity has been described in several tumor cell lines, which is possibly mediated by induction of apoptosis and alterations of the cell cycle. Organosulfur compounds in garlic are thus possible cancer-preventive agents. Clinical trials will be required to define the effective dose that has no toxicity in humans.