Flavonoids, a group of biologically active compounds, are present in plants in the form of aglycones as well as glycosides in which the saccharide residue is connected to the aglycone with an O-glycoside bond or, less frequently, with a C-glycoside one. Similarly to flavonoid O-glycosides, flavonoid C-glycosides are characterised by antioxidant, anti-inflammatory, hepatoprotective, spasmolytic, hypotensive, sedative, antimicrobial, antiviral, cytotoxic and radiation-protective activity. For some flavonoid C-glycosides, antidiabetic and cardiac muscle strenghtening activity is also typical. Vasoprotective or diuretic activity, characteristic for many flavonoid O-glycosides, has not been found so far.