TA/TT mechanisms - oxidative TA/T mechanisms - non-oxidative Creativity and innovation leads to discovery Proposed role of Co-pigmentation Anthocyanins and Procyanidins You are here Oak and Oxygen
Procyanidins = Seed Tannins 
Prodelphinidins = Skin Tannins 
There are two major classes of condensed tannins (or as they are known more properly, polyphenolics) naturally occuring in grapes.
  The only difference between the two classes is the presence of one additional hydroxyl group on the B ring of the three ring structure for prodelphinidin.
  The names for the two classes are derived from the following: when a polymer of procyanidin is hydrolyzed in strong acid, it will yield anthocyanidin cyanidin; prodelphinidin will yield delphinidin.

  This strucure represents a longer procyanidin structure with the lower terminal unit and subsequent extension units of either catechin or epicatechin.
  A gallic acid may be esterified to the 3 position, which would increase the hydrophobicity at the center of the oligomer or polymer.

Structure of the main procyanidin dimers from V. Vinifera
main procyanidin structure The upper two structures illustrate examples of dimers of eppicatechin and catechin, each bonded between the 4 position of the upper molecule and the 8 position of the lower molecule. The configuration cis or trans of the bond between the C and B rings with the hydroxyl located on the 3 position of the C ring determines whether or not the structure is epicatcechin (cis) or catechin (trans).
  The lower set of structures shows bonding between the 4 and 6 positions which would cause branching of longer oligomers of polymers.