Garlic: Allyl Sulfur Compounds and Cancer Prevention

Garlic, Allium sativum L., is a plant within the family Alliaceae that has been widely used for its culinary and medicinal properties. This plant contains organosulfur compounds with allyl groups such as allyl mercaptan (AM), S-allyl cysteine (SAC), diallyl trisulfide (DATS) and has been responsible for different health benefits such as antihypertensive, anticoagulant, anti-inflammatory, antimicrobial and anticancer. Especially some lipid-soluble allyl sulfur compounds can inactivate carcinogens and reduce cancer risk and regulate the cellular processes. Epidemiological studies have shown that garlic and its components can decrease the incidence of human stomach, colon, prostate, brain, skin, breast, lung, uterine, and esophagus cancers. These anticarcinogenic effects appear to be achieved by modifying common signaling pathways. But allyl sulfur compounds have different effect in supressing tumor proliferation. Therefore, the compounds that are responsible for the cellular and molecular effects, the stages which they suppress neoplasia and interactions with other drugs should be very well known. Tumor supression ability of allyl sulfur compounds of garlic is attributed the stimulation of detoxification enzymes, protection from oxidative stress, induction of cell apoptosis and cell cycle arrest, prevention of chromosomal damage, induction of immune system and supression of nitrosamine bioactivation. On the other hand, not only the genetic mechanisms, but also the epigenetic mechanisms can be associated with the cancer prevention. Garlic and its several allyl sulfur compounds can be modified by both DNA methylation and histon acetylation. In this chapter, preclinical and clinical studies on the effects of garlic consumption in reducing cancer prevalence will be presented in detail. Furthermore, studies involving the use of allyl sulfur compounds individually or in combination will be discussed and their mechanisms of action will be interpreted at cellular and molecular level.