Studies on flavonoid metabolism. Biosynthesis of (+)-[14C]catechin by the plant Uncaria gambir Roxb.

1. The formation of (+)-[(14)C]catechin has been demonstrated in Uncaria gambir after the administration of (14)CO(2) and [1-(14)C]acetate. 2. By alkaline degradation to phloroglucinol and protocatechuic acid it has been shown that administration of (14)CO(2) resulted in equal labelling of the A and B rings of catechin, whereas [1-(14)C]-acetate gave rise to labelling largely in the A ring. 3. Incorporation of (14)C from both (14)CO(2) and [1-(14)C]acetate into (+)-catechin was greater in young than in older leaves.