Plant
phytoalexins are a class of low molecular weight compounds that accumulate in response to biotic and abiotic elicitors such as pathogens, wounding, freezing, UV light, and exposure to
agricultural chemicals.
Phytoalexins have been identified in at least 75 plants including cruciferous vegetables, soybean, garlic, tomato, rice, beans, and potatoes suggesting plants may be a rich source of
cancer-fighting compounds. Preclinical evidence suggests these compounds possess anticancer properties including an inhibition of microbial activity, cell proliferation, invasion and
metastasis, hormonal stimulation, and stimulatory effects on expression of metabolizing
enzymes. This review highlights the plausible molecular mechanisms through which
phytoalexins regulate biological processes that can impinge
cancer development. Targets of
phytoalexins include signal transduction pathways,
transcription factors, cell cycle checkpoints, intrinsic and extrinsic apoptotic pathways, cell invasion and
matrix metalloproteinase,
nuclear receptors, and the phase II detoxification pathway. Additional research should address physiological relevant dietary concentrations, combinations of
phytoalexins and interactions with other dietary compounds, duration of exposure, and tissue specificity as variables that influence the effectiveness of
phytoalexins on normal and cancerous processes.