Metabolism of the cinnamon constituent o-methoxycinnamaldehyde in the rat

Abstract

1. The metabolism of o-methoxycinnamaldehyde (1·3 mmol/kg, intragastrically) was studied in rats.

2. Identification of the urinary metabolites by g.l.c.-mass spectrometry and quantification by h.p.l.c. showed that the major metabolic pathway (approx. two-thirds of the dose) was oxidation to the corresponding cinnamic and phenylpropionic acids (C₆-C₃ acids) which were largely excreted as glycine conjugates.

3. Intermediate amounts (approx. 10% of the dose) of the O-demethylated C₆-C₃ acids were excreted.

4. Relatively large amounts of the β-hydroxylated phenylpropionic acid derivative were found, however only traces of the further products of β-oxidation (2-methoxylated derivatives of benzoic and hippuric acid) were excreted.

5. No evidence was obtained for conjugation of o-methoxycinnamaldehyde with glutathione.

6. Urinary excretion of metabolites was rapid (91% in 24h and 98% in 48 h).