Carbon-14 biolabeling of (+)-catechin and proanthocyanidin oligomers in willow tree cuttings

Proanthocyanidin polymers, oligomers, and the structurally related monomer (+)-catechin were labeled by incorporation of radioactive precursors in sho ots of willow tree (Salix caprea L.). [1-C-14]-Acetate and [U-C-14]-phenyla lanine precursors were fed through the cut stems or petioles of leaves. Opt imization of several parameters such as the nature and origin of the plant material, leaf maturity, nature, and quantity of radioactive precursor appl ied and the duration of metabolism led to incorporation yields of 3.2% and to specific activities of 500 mu Ci/g. Detailed characterization of the pro ducts (polymerization degree, procyanidin/prodelphinidin ratio, specific ac tivities) and purification by chromatography are reported. Some sugars boun d to radiolabeled proanthocyanidin polymers were removed by enzymic treatme nt with a mixture of glycosidases. A radioactive purity close to 100% and s pecific activities suitable for bioavailability studies were obtained.