The metabolism and lymphatic transport of γ-oryzanol in rats were investigated following oral administration of the 14C-labeled compound (triterpenyl esters of ferulic acid-3-14C). Redioactivity excreted in the urine during 72 h after oral administration was 9.8% of the dose (50 mg/kg). Unchanged γ-oryzanol was not detected at all in the urine, but an in situ intestinal absorption experiment suggested that more than 80% of the absorbed radioactivity was transferred into the mesenteric vein as an intact form, though a part was metabolized in the small intestine during absorption. Ferulic acid, dihydroferulic acid, m-hydroxyphenylpropionic acid, m-coumaric acid, m-hydroxyhippuric acid and hippuric acid were identified as the major urinary metabolites. These metabolites, with the exception of hippuric acid, were also excreted in the form of glucuronide or sulfate. The radioactivity transported into the thoracic duct was only 0.3% of the dose, and of this, more than 80% was found to be γ-oryzanol by thin-layer chromatography. From these results, it is considered that γ-oryzanol administered orally is absorbed mainly into the blood via the portal vein system, not into the lymph via the thoracic duct.
