Abstract

Natural polyphenols are a wide class of secondary plant metabolites and represent an abundant antioxidant component of human diet. An important, but often neglected, group of natural polyphenols are tannins. This review offers a general description of chemistry of hydrolysable and condensed tannins (proanthocyanidins), and phlorotannins, the mechanisms of their antioxidation action, like free radical scavenging activity, chelation of transition metals, inhibition of prooxidative enzymes and lipid peroxidation. The mechanisms of action of inhibition of various enzyme systems, antibacterial, antiviral, antiprotozoal, anticarcinogenic, antidiabetic, hepatoprotective, cardiovascular system preventing, immunomodulation, antiallergic and anti-inflammatory effects as well as the absorption, metabolic fate and positive in vivo effects of tannins are enclosed.