Enzymatic or non-enzymatic oxidation is the most common reaction involved in the production of secondary polyphenols. Polyphenols having ortho-diphenol (catechol) aromatic rings are widely distributed in nature and susceptible to oxidation. The structure of dehydrodicatechin A (Figure 1) was first reported in 1969 [8], and generation of related catechin dimers and trimers by in vitro experiments followed [9,10]. These compounds are produced by nucleophilic addition of electron-rich phloroglucinol A-rings to the electron-deficient ortho-quinone of B-rings. In the case of dehydrodicatechin A, further oxidation of the catechol ring and addition of hydroxyl groups to a double bond and a ketone occurs (Scheme 1). These types of oxidation products are partly responsible for the browning of fruits and beer [11]. The in vitro oxidation of (+)-catechinvia an oxidation enzyme usually yields a complex mixture, including oligomers, because each catechin molecule has three reaction sites: the C-6 and C-8 of the A-ring and the C-6 of the B-ring [12]. Catechin oxidation products related to these compounds have also been isolated from Quercus ilex [13] and some crude drugs