Metabolism of rosmarinic acid in rats

The urine of rats administered rosmarinic acid (7) orally contained seven metabolites, which were identified as trans-caffeic acid 4-O-sulfate (1), trans-m-coumaric acid 3-O-sulfate (2), trans-ferulic acid 4-O-sulfate (3), trans-caffeic acid (4), m-hydroxyphenylpropionic acid (5), trans-m-coumaric acid (6), and unchanged rosmarinic acid (7) by spectroscopic and chemical data. The total cumulative amount of 1-7 excreted in the urine 48 h after the oral administration of rosmarinic acid was approximately 31.8% of the dose administered. On the other hand, the metabolites attributed to rosmarinic acid could not be found in the bile. Orally administered rosmarinic acid may thus be concluded to be excreted in the urine rather than in the bile, with cleavage of ester bonds, selective para-dehydroxylation, methylation, and sulfate-conjugation. Metabolites 2, 3, 5, and 6 were also detected in the plasma.