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S. JOVANOVIC, Helix International, 381 Viewmount Dr., Nepean, ON K2E 7R9, Canada and C. Boone, National Institutes of Health, Bethesda, MD.

The use of phytochemicals as cancer prevention and anti-aging agents has been thoroughly explored, both in vivo and in vitro. However, chemical, biochemical, and pharmacological mechanisms of food phenolics remain elusive.

Inactivation of crucial enzymes as well as binding to receptors inhibits growth and induces apoptosis of cancer cells, prevents inflammatory response of surrounding healthy tissues, and inhibits angiogenesis. Chemical antioxidant action will support biochemical and pharmacological function at all levels. Because of favorable redox properties, food phenolics efficiently inactivate oxyl radicals, such as hydroxyl, peroxyl, or alkoxyl, and repair amino acid and DNA base radicals. Epigallocatechin gallate and gallocatechin from green tea are synergists of vitamin E and curcumin, thus enhancing their beneficial action. Flavonoids are also extremely potent iron (II) and iron (III) chelators, which may prevent damage from unbound iron.

Bioavailability of food phenolics is crucial for their efficiency as anti-cancer and anti-aging remedies. For example, water-soluble tea catechins are readily absorbed through the gut. About 70–80% of ingested catechins enter circulation. In liver, a large part (about 90%) of ingested catechins is methylated, sulfated, or complexed with glucoronic acid. About 2–5% of ingested catechins remain intact in systemic circulation. Peak concentrations are barely sufficient for inhibition of enzymes, and binding to receptors, but may support chemical antioxidant function.

What is the basis of cancer prevention and aging retardation by food phenolics? Is it their ability to scavenge free radicals, inactivation of enzymes, or binding to specific receptors? How are pharmacodynamics and pharmacokinetics of food phenolics affected by other constituents of food? Are they more bioavailable when taken alone, or in combination with other foodstuffs? The mechanisms of food phenolics as anti-cancer and anti-aging remedies will be discussed in light of their bioavailability, synergism with other antioxidants, and food constituents and dynamics of their action and excretion.