Hagerman condensed tannin structural chemistry Further polymerization can yield the linear 4.8 polymers such as the Sorghum procyanidin. Linear polymers based on 4,6 dimers;and branched dimers containing both 4,6 and 4,8 linkages are less common picatechin-catchin Although the term conde sed tannin is still widely used to describe these flavonoid-based polyphenolics,the chemically more descriptive term"proanthocyanidin"is gaining acceptance Proanthocyanidins are compounds that yield anthocyanidin pigments upon oxidative cleavage (NOT hydrolysis)in hot alcohols,e.g.via acid butanol chemistry. OH in2 46->8 catechir a2ena8n+eng8gop Hagerman condensed tannin structural chemistry 3/6 Further polymerization can yield the linear 4,8 polymers such as the Sorghum procyanidin. Linear polymers based on 4,6 dimers; and branched dimers containing both 4,6 and 4,8 linkages are less common. Although the term condensed tannins is still widely used to describe these flavonoid-based polyphenolics, the chemically more descriptive term “proanthocyanidin” (NOT hydrolysis) in hot alcohols, e.g.via acid butanol chemistry. is gaining acceptance. Proanthocyanidins are compounds that yield anthocyanidin pigments upon oxidative cleavage HO O OH OH OH OH O O O OH OH OH HO OH OH OH HO OH OH OH OH OH OH HO O+ OH OH HO OH OH procyanidin epicatechin2 4β−−>8 catechin 2 cyanidin + catechin (extender) end group H+ H+ 2 O O OH HO HO OH OH OH OH HO O OH OH OH OH OH OH OH 15 Sorghum procyanidin epicatechin-[(4β->8)-epicatechin]15-(4β->8)-catechin