Flavonoids are a part of plants polyphenols and are quite differentiated. They are widespread in the plant kingdom where play an important role protect against ionizing radiation and to provide coloration (plant pigments) function as antioxidants and natural substances protecting plants against pathogens. They are a daily component of our diet and their daily intake is ~1 g (37). Flavonoids, particularly anthocyanins, have a confirmed anti-arteriosclerotic and preventive effect in the cardio-vascular disease (37-44). These substances are very weakly absorbed in the alimentary tract and, in case of anthocyanins, it was showed that only 0.1% of their amount present in the diet is absorbed (43). At present it is known that not the anthocyanins themselves have the anti-arteriosclerotic effect but their well absorbed metabolite protocatechuic acid (PCA) (43). Anthocyanins at first are bio-transformed into Cyanidin-3-O-beta-glucoside, which is next metabolized by bacteria present in the large intestine to above mentioned PCA (fig. 2).