B type proanthocyanidins are a specific type of proanthocyanidin

Proanthocyanidin

Proanthocyanidins, also known as OPCs or condensed tannins, are a subgroup of the flavonoid class of polyphenols...

, which are a class of flavanoids. They are oligomer

Oligomer

In chemistry, an oligomer is a molecule that consists of a few monomer units , in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers, and tetramers are oligomers. Many oils are oligomeric, such as liquid paraffin...

s of flavan-3-ol

Flavan-3-ol

Flavan-3-ols are a class of flavonoids that use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. These compounds include the catechins and the catechin gallates....

s.

Dimeric B type proanthoanthocyanidins

These molecules have the molecular formula C₃₀H₂₆O₁₂ (molar mass : 578.52 g/mol, exact mass : 578.142426).

Molecules with 4→8 bonds

The 4-8 bond can be in the alpha or in the beta position.

• Proanthocyanidin B1
  Proanthocyanidin B1
  Proanthocyanidin B1 is a B type proanthocyanidin.It is a molecule with a 4→8 bond . Proanthocyanidin-B1 can be found in Cinnamomum verum , in Uncaria guianensis , and in Vitis vinifera ....
  
   or epicatechin-(4β→8)-catechin
• Proanthocyanidin B2
  Proanthocyanidin B2
  Proanthocyanidin B2 is a B type proanthocyanidin .Proanthocyanidin B2 can be found in Cinchona pubescens , in Cinnamomum verum , in Crataegus monogyna , in Uncaria guianensis ,...
  
   or (-)-epicatechin-(4β→8)-(-)-epicatechin
• Proanthocyanidin B3
  Proanthocyanidin B3
  Proanthocyanidin B3 is a B type proanthocyanidin.Proanthocyanidin B3 is a catechin--catechin. It can be found in barley,and in beer....
  
   or catechin-(4β→8)-catechin
• Proanthocyanidin B4
  Proanthocyanidin B4
  Proanthocyanidin B4 is a B type proanthocyanidin.Proanthocyanidin-B4 is a catechin--epicatechin dimer. It is found in the litchi pericarp, in grape seeds, and, along with 4-cis-isomer of procyanidin B4, in beer....
  
   or catechin-(4α→8)-epicatechin

Molecules with 4→6 bonds

• Proanthocyanidin B5
  Proanthocyanidin B5
  Proanthocyanidin B5 is a B type proanthocyanidin.Proanthocyanidin B5 is an epicatechin--epicatechin dimer. It can be found in grape seeds and in Hibiscus cannabinus root and bark....
  
   or epicatechin-(4β→6)-epicatechin
• Proanthocyanidin B6
  Proanthocyanidin B6
  Proanthocyanidin B6 is a B type proanthocyanidin.Proanthocyanidin B6 is a catechin--catechin dimer. It can be found in grape seeds and in beer....
  
   or catechin-(4α→6)-catechin
• Proanthocyanidin B8
  Proanthocyanidin B8
  Proanthocyanidin B8 is a B type proanthocyanidin.Proanthocyanidin B8 is a catechin--epicatechin dimer. It can be found in grape seeds and in beer....
  
   or catechin-(4α→6)-epicatechin

Trimers

• Proanthocyanidin C1
  Proanthocyanidin C1
  Proanthocyanidin C1 is a B type proanthocyanidin. It is an epicatechin trimer found in grape ....
  
   or epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin
• Arecatannin B1
  Arecatannin B1
  Arecatannin B1 is a B type proanthocyanidin found in the betel nut. It is an arecatannin trimer with a 4β→6 bond.-External links:*...
  
   or epicatechin-(4β→8)-epicatechin-(4β→6)-catechin

Chemistry

B-type procyanidin (catechin

Catechin

Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....

 dimer) can be converted to A-type procyanidin

A type proanthocyanidin

A type proanthocyanidins are a specific type of proanthocyanidin, which are a class of flavanoid. Proanthocyanidins fall under a wide range of names in the nutritional and scientific vernacular, including oligomeric proanthocyanidins, flavanoids, polyphenols, condensed tannins, and OPCs....

by radical oxidation.