Phlobaphene
Phlobaphenes (or phlobaphens, CAS No.:71663-19-9) are reddish, alcohol-soluble and water-insoluble phenolic substances. They can be extracted from plants, or be the result from treatment of tannin extracts with mineral acids (tanner's red). The name phlobaphen come from the Greek roots φλoιὀς (phloios) meaning bark and βαφή (baphe) meaning dye.
No biological activities have currently been reported for phlobaphenes. Phlobaphenes from hawthorn fruits (Fructus Crataegi) may have a specific action on the coronary circulation. They are converted into humins in soils.
Natural phlobaphenes are the common bark, pericarp, cob glume and seed coat (testa) pigments. They have not been found in flowers, unless the brown and black pigments in the involucrum of certain compositae are found to be of the phlobaphen type.
In bark, phlobaphenes accumulate in the phellem layer of cork cambium, part of the suberin mixture.
Many cinchona barks contain a particular tannin, cinchotannic acid, which by oxidation rapidly yields a dark-coloured phlobaphene called red cinchonic,cinchono-fulvic acid or cinchona red.
They are common in redwoods barks like Sequoia sempervirens or in oak barks where the chief constituent, quercitannic acid, a molecule also present in quercitron, is an unstable substance, having a tendency to give off water to form anhydrides (phlobaphenes), one of which is called oak-red (C28H22O11).
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