Chemoprevention of Colon Carcinogenesis by Dietary Non-nutritive Compounds

In addition to mutagens and/or carcinogens a number of modulators of carcinogenesis are present in our environment. Some of them are contained in our regular foods and therefore dietary factors play a role in the development of some types of cancers including colon cancer. Epidemiological studies have suggested that a diet rich in fruits and vegetables is associated with reduced risk for a number of common cancers. There are still many unknown constituents and/or factors in foods that could either enhance or reduce the possibility of developing cancer. Animal studies of experimental chemical carcinogenesis have indicated that several non-nutritive components in foods, belonging to different chemical groups, protect against certain types of cancers including colonic neoplasms. These chemicals are known as "chemopreventive agents". Many of them are antioxidants and might suppress carcinogenesis through: (I) inhibiting Phase I enzymes; (ii) induction of Phase II enzymes; (iii) scavenging DNA reactive agents; (iv) suppression of hyper-cell proliferation induced by carcinogens; and/or (v) inhibition of certain properties of neoplastic cells. With the continuing increase in the incidence of colon cancer, there is an ever increasing need to determine the most effective means for prevention and to understand the underlying mechanism(s). Previous studies in our laboratory demonstrated protective effects of several naturally occurring products against rat colon tumorigenesis. This article will introduce our recent studies in our search for chemopreventive effects of flavonoids (diosmin and hesperidin) and other phytochemicals in edible plants on rat colon carcinogenesis.