EN
The occurrence, biosynthesis and biological properties of the flavonols as well as their importance for human health were reviewed. Flavonols are the main group of large flavonoids class. In plant tissues widely occur the quercetin and its glycosides in much smaller levels the glycosides of kaempferol, and occasionally- the myricetin. The highest concentration of quercetin glycosides was found, among the food components, in onion and other Allium vegetables. Other important sources of flavonols are the tea infusions and apples, although the bioavailibility rate of the flavonols from onion was much higher than those of tea and apples. It was found that the quercetin and other flavonols reveal the strong antioxidant and antiradical properties. Quercetin shows a protective activity in LDL oxidation and therefore it is important at heart disease prevention. Most likely the flavonols show some anticancer properties, too.