Flavonoids are polyphenolic secondary plant metabolites which commonly exist as multiple 0-and C-glycosidic derivatives (1,2), but also may be present as aglycones (3). They are an important part of the human diet (4-6) -consider the recent discussions on the connection between red wine consumption and reduced risk of heart diseases, the socalled "French paradox" (7-9) or the studies on the proanthocyanidin ingredients in green tea (10,11). They are also considered the active principle in a number of medicinal plants (12,13). Owing to these potential benefits to human health, polyphenolic plant metabolites are the major class of the recently popular phytochemicals (14,15). Early in the beginning of the research into the structures and functions of flavonoids, their antioxidative capacities, particularly with respect to stabilizing foodstuffs, was recognized (16,17). Up to now, this has remained the most important topic of investigation, despite the fact that various other functions have been attributed to them over the years. For instance, they are mutagenic yet they are also anticarcinogens; they exhibit biocidal effects and have antifertility properties, yet express beneficial effects in inflammatory and immunomodulatory systems and interact with signal transduction processes (Table 1).