ABSTRACT
It is generally accepted by the scientic community that polyphenols are bene- cial for humans. They are mainly regarded as life-extending antioxidants because they efciently scavenge oxidant species, notably free radicals. This assumption is based on the free radical theory of aging proposed by Denham Harman in his 1956 paper (Harman, 1956). He wrote: “Aging and the degenerative diseases associated with it are attributed basically to the deleterious side attacks of free radicals on cell constituents and on the connective tissue.” Free radicals and other oxidative species such as hydrogen peroxide trigger oxidation of biomolecules such as DNA, proteins, and lipids; Harman suggested later that “dietary manipulations [are] expected to lower the rate of production of free radical reaction damage” (Harman, 1981). To Harman, these manipulations would essentially consist of reducing intake, but to many others, it followed logically from his theory that any agent with a capacity to scavenge free radicals would, in principle, prevent degenerative diseases and delay aging through an “antioxidant” action. Naturally occurring phenolic compounds arose as one of the main candidates for antioxidants. Already in 1936, Rusznyák and Szent-Györgyi had described avonols as active health-promoting agents in the absence of ascorbic acid (vitamin C) and called them vitamin P (Rusznyák and Szent-Györgyi, 1936). Later, the association of the free radical scavenging activity of avonols and other phenolics with the promotion of health aroused scientic interest for polyphenols as chemopreventive agents (Herrmann, 1973; Huang et al., 1992). This has now expanded from the scientic community to the general population.
