Incorporation of [C]Phenylalanine into Flavan-3-ols and Procyanidins in Cell Suspension Cultures of Douglas Fir.

L-[(14)C]Phenylalanine, fed to cell suspension cultures of Douglas fir, (Pseudotsuga menziesii Franco) was incorporated simultaneously, but at different rates, into (+)-catechin, (-)-epicatechin, and procyanidins of increasing molecular weight. Asymmetric labeling of dimers and polymers was demonstrated, with more label appearing in the upper than in the lower or terminal unit. In addition, the total pool of free monomers was 10 to 30 times more highly labeled than was this lower, terminal unit of dimers and higher oligomers. Since the dimer, epicatechin-catechin, contained more label than catechin-catechin, it is concluded that the carbocation with the 2,3-cis stereochemistry of (-)-epicatechin was formed more rapidly than was that of the 2,3-trans type of (+)-catechin.