在苹果，可可豆和肉桂提取物中测定A型和B型花青素

　　Procyanidins are condensed tannins consisting of polymerized subunits of epicatechin or catechin. They are structurally highly diverse because of the many possible combinations based on number of subunits, type of bonding, and branching. For convenience, procyanidins are typically characterized based on their degree of polymerization, with DP2 representing a dimer, DP3 a trimer, and so on. Procyanidins can be further distinguished by the type of bonding between subunits. For example, in B-type procyanidins (apples, cocoa) the subunits are connected by a single bond, which is predominantly 4β8 or less often 4β6. In apples and cocoa, the 4β8 bond between connected epicatechin units occurs in the dominant components of various oligomers, as represented by the dimer B2, trimer C1, and tetramer D, etc. The dimeric B-type procyanidins occurring in nature are represented by all 8 structures shown in Figure 1. In A-type procyanidins (e.g. cinnamon, cranberries, and peanuts) an additional bond between adjacent subunits occurs that is often between 2β7. The existence of an A-type bond imposes on the molecule a more rigid, compact structure.