Urinary excretion of hydroxycinnamates and flavonoids after oral and intravenous administration

The urinary recoveries of the hydroxycinnamates, ferulic acid (3-methoxy, 4 -hydroxy cinnamic acid), and chlorogenic acid (the quinic acid ester of 3,4 -dihydroxycinnamic acid), and three structurally related flavonoids were st udied in the rat. For the latter, the aglycone quercetin was compared with its 3-glucoside (isoquercitrin) and 3-rhamnoglucoside (rutin). Doses of 50 mg/kg were administered via the oral and intravenous routes and urine colle cted over the subsequent 24-h period. Reverse phase HPLC with photo-diode a rray detection was used to analyze the unchanged compound and their metabol ites excreted in the urine. Ferulic acid and isoquercitrin were orally abso rbed (5.4 and 0.48% of administered dose,respectively)and are therefore bio available. In contrast, neither unchanged chlorogenic acid, rutin, querceti n, nor the conjugated metabolites in the form of glucuronide or sulphate we re detected in the urine after oral dosing. All the flavonoids studied prod uced low total urinary recoveries after intravenous administration,9.2% for quercetin-3-rhamnoglucoside, 6.7% for the 3-glucoside, and 2.4% for the ag lycone, indicating that extensive metabolism to low molecular weight compou nds or excretion via other routes may be occurring. Overall it can be state d that renal excretion is not a major pathway of elimination for intact fla vonoids and hydroxycinnamates in the rat. (C) 1999 Elsevier Science Inc.