C-prenylated flavonoids with potential cytotoxic activity against solid tumor cell lines

Abstract: Natural products of plant origin or their semisynthetic derivatives acting as chemopreventive or chemotherapeutic agents for various types of cancer are under study as potential new anticancer drugs. Within the huge class of plant phenolic secondary metabolites, the subclass of prenylated flavonoids is quite rich in structural variety and pharmacological activity. One of their most prominent characteristics is their potential as anticancer agents. The aim of this review is to summarize the available data about the cytotoxicity of C-prenylated flavonoids on solid tumor cell lines as shown by in vitro assays. Prenylated flavonoids are divided into groups according to the prenyl substitution of the flavonoid skeleton. Within these flavonoid groups, attention is focused on flavones, flavonols, flavanones, dihydroflavonols, and isoflavonoids. This search is limited to compounds that do not contain heteroatoms other than oxygen, and is focused only on aglycones. Attempts to compare the bioassay results obtained from the search reveal complications caused by the use of different assay protocols, different ranges of concentration studied, different times the cell cultures were exposed to the compounds being assayed, and in some cases the lack of a proper positive control. In vivo assays of the anticancer activity of prenylated flavonoids on solid tumors were also reviewed. Despite the difficulties in comparing them, it is clear that the C-prenylated flavonoid class possesses significant bioactivity, suggesting a potential role for such compounds in anticancer drug discovery and development.