Antiproliferative and cancer chemopreventive activity of phytoalexins: focus on indole phytoalexins from crucifers.

Phytoalexins are produced by plants after exposure to physical, biological or chemical stress and a specific group of these metabolites represent indole phytoalexins produced by important plants of the family Cruciferae. With respect to the epidemiologically proven cancer chemopreventive properties of brassica vegetables, antiproliferative and anticarcinogenic activities of indole phytoalexins have been studied. Several indole phytoalexins (i.e. brassinin, spirobrassinin, brassilexin, camalexin, 1-methoxyspirobrassinin, 1-methoxyspirobrassinol and methoxyspirobrassinol methyl ether) have been found to possess significant antiproliferative activity against various cancer cells and this activity is supposed to be associated with the modulation of activity of transcription factors regulating cell cycle, differentiation and apoptosis. Indole phytoalexins (i.e. cyclobrassinin, spirobrassinin, brassinin) also exhibited cancer chemopreventive activity in models of mammary and skin carcinogenesis. Understanding the molecular and cellular mechanism of action of such drugs and their structure-activity relationships is necessary for development new derivatives with more favourable profile of antiproliferative and chemopreventive activities.