[Biologically active substances of plant origin. Flavonols and flavones: prevalence, dietary sourses and consumption]

Flavonoids are the most numerous group of natural polyphenolic compounds, the secondary metabolites of plants that may play an important role in human health protection. Flavonols and flavones constitute the main two classes of flavonoids, whose antioxidant properties and high biological activity have been proofed both in vitro and in vivo. This review summarizes data, concerning the structure, occurrence and content of the main flavonols (quercetin, kaempherol, myricetin, isorhamnetin) and flavones (apigenin, luteolin) in some most widely consumed foodstuffs, including vegetables, fruits, berries, nuts, beverages and other products of plant origin. The products with high content of these biologically active food compounds--the major dietary sources of them--are noted. Forms of flavonols and flavones more often distributed among edible plants are characterized and some of their known glycosides occurred in foods are enumerated. Some peculiarities, characteristic to flavonol sand flavones glycosilation (O- and/or C-glycosides formation) are described. The data for flavonol and flavone glycosides composition (profiles) of some commonly consumed commodities rich by these flavonoids (onions, cabbage, apples at al.) are shown. Information about levels of daily dietary intake of total and individual flavonols and flavones in several countries is presented. The questions about dietary habits and lifestyle factors and the contribution of certain foods to flavonols and flavones in daily dietary consumption values are also discussed.