Antioxidant phytochemicals incancer prevention and therapy—Anupdate

Abstract

Free radicals play key roles in normal cellular processes. However, when excessively produced, these short half-life molecules damage many cellular components, including proteins, lipids, and nucleic acids. Dietary carotenoids, tocols, ascorbic acid, and phenolic compounds counteract free radicals, improving the cellular redox status and promoting the growth arrest of cancer cells in a structure-dependent manner. Other chemopreventive actions include proapoptosis, disruption of DNA synthesis, intracellular signaling, immunomodulation, and antiangiogenesis. The bioactivity of these antioxidants also depends on an effective bioavailable concentration that in turn depends on their intestinal bioaccessibility and first-pass metabolism. The free radical theory of cancer has been challenged by the nucleophilic tone and para-hormesis theories. New information indicates that certain antioxidants are also proantioxidants that stimulate cancer progression and metastasis. Research on the effectiveness of plant antioxidants in cancer therapy (secondary prevention) derived from well-designed prospective investigations is needed to disentangle this controversy.