Metabolism of 3-(Hydroxymethyl)-8-methoxychromone in the Rat: II. Classification and Identification of Urinary Drug Metabolites

1. Five metabolites were isolated from the urine of dogs dosed with 3-(hydroxymethyl)-8-methoxy[4-14C]chromone. These were identified as 8-methoxychromone, 2-hydroxy-3-methoxyacetophenone, 3-(hydroxymethyl)-8-hydroxychromone, 8-hydroxychromone and 2,3-dihydroxyacetophenone. 2. These compounds were also present in the urine of rats treated with labelled drug, together with unchanged drug and two intermediate metabolites, 3-carboxy-8-methoxychromone and 3-(carboxymethyl)-8-hydroxychromone. 3. In addition to the unconjugated labelled compounds, glucuronides and sulphates were identified. 4. Quantitative data were obtained for all of the 20 labelled compounds in rat urine. 5. A scheme is presented for the biotransformation of 3-(hydroxymethyl)-8-methoxychromone in rats and dogs, and a mechanism for scission of the γ-pyrone ring is suggested.