It is a molecule with a 4→8 bond (epicatechin-(4β→8)-catechin). Proanthocyanidin-B1 can be found in Cinnamomum verum (Ceylon cinnamon, in the rind, bark or cortex), in Uncaria guianensis (cat's claw, in the root), and in Vitis vinifera (common grape vine, in the leaf) or in peach.
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