1. Introduction
A variety of bioactive compounds and their derivatives has been shown to inhibit carcinogenesis in a number of experimental systems involving initiation, promotion and progression (Ho et al., 1994 and Huang et al., 1994). Plants contain abundant quantities of these substances and have consistently been shown to be associated with a lower risk of cancers at almost every site (Steinmetz and Potter, 1991). Efforts, therefore, are being made to identify naturally occurring anticarcinogens which would prevent, slow and/or reverse the cancer induction and its subsequent development (Chuang et al., 2000).