Studies on flavonoid metabolism. Metabolism of (+)-[¹⁴C]catechin in the rat and guinea pig

1. The fate of (+)-[U−¹⁴C]catechin and (+)-[ring A−¹⁴C]catechin has been studied in the guinea pig and rat. 2. (+)-[U−¹⁴C]Catechin was shown to give rise to labelled phenolic acids, labelled phenyl-γ-valerolactones and ¹⁴CO₂. 3. (+)-[ring A−¹⁴C]-Catechin did not give rise to labelled phenolic acids, but labelled phenyl-γ-valerolactones were detected together with a higher proportion of ¹⁴CO₂. 4. Administered [¹⁴C]δ-(3-hydroxyphenyl)-γ-valerolactone gave rise to labelled m-hydroxyphenylpropionic acid in the rat whereas administered [¹⁴C]m-hydroxyphenylpropionic acid gave rise to a compound yielding labelled m-hydroxybenzoic acid on hydrolysis. 5. The distribution of radioactivity in the urine and faeces of (+)-[¹⁴C]catechin-fed animals is described; a high proportion of residual radioactivity was found in urine that had been exhaustively extracted with diethyl ether.