Polyphenols are secondary plant met

Polyphenols are secondary plant metabolites that have received much attention because of their potential health benefits. They include tannins, compounds with molecular masses typically ran- ging between 500 and 3000Da [1,2], though some have much higher masses up to 20,000Da [2]. Tannins are esters of sugars and phenol carbonic acids or polycondensates of catechins (flavan- 3-ol) [3,4]. They are classified on the basis of their structure into two groups: the hydrolysable and the condensed tannins [3]. Tan- nins are characterized by high chemical activity and a variety of biological effects such as antitumor, antimutagen, antimicro- bial, antiviral, antiplatelet, hypoglycemic and antiinflammatory
[3–5]. Various effects of tannins are assumed to be connected not only to their antiradical action but also to their interactions with enzymes, receptors and transcription factors. The antioxidant activity is associated with inhibition of pro-oxidant enzymes. In particular, ellagitannins inhibit xanthine oxidase [6] and proantho- cyanidins inhibit COX-2 (cyclooxygenase-2) and iNOS (inducible nitric oxide synthase) [7]. Polyphenols can decrease the expression of prooxidative enzymes by regulating NF-