(S)-Dihydrooroxylin A in human urine following oral administration of the traditional Chinese medicines: Daisaiko-to and Shosaiko-to

Abstract Dihydrooroxylin A was isolated and characterized from human urine collected after oral administration of traditional Chinese medicines, Daisaiko-to and Shosaiko-to ( Dachaihu-tang and Xiaochaihu-tang in Chinese, respectively). Spectroscopic data (UV, CD, 1 H NMR and MS) and chiral HPLC analysis revealed that this compound had the S -configuration (80% ee). This is the first example of stereoselective hydrogenation of a substituted flavone into its corresponding flavanone in the human body.