Complex tannins are defined as tannins in which a catechin unit (1.39) is bound glycosidically to either a gallotannin or an ellagitannin unit. As the name implies, the structure of these compounds can be very complex. An example is Acutissimin A (1.99). This is a flavogallonyl unit bound glucosidically to C1, with an additional three hydrolyzable ester bonds to a D-glucose-derived open-chain polyol.
This complex tannin is formed during the aging process of red wine, whereby the catechin unit originates from the grapes, and the ellagitannin, in this case vescalagin, originates from the oak barrels.
Acutissimin A has been shown to be a powerful inhibitor of DNA topo-isomerase II, an enzyme required for the division of cancer cells, and a target for chemotherapeutic drugs (Quideau et al., 2003). Based on these findings, however, it is an overstatement to consider red wine a cancer preventative. Red wine contains other compounds with medicinal activity which will be discussed in more detail in Chapter 7.
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