Isolation and identification of urinary metabolites of kakkalide in rats

Kakkalide is a major isoflavonoid from the flowers of Pueraria lobata (Willd.) Ohwi, possessing the protective effect against ethanol-induced intoxication and hepatic injury. The metabolism of kakkalide was investigated in rats. Thirteen metabolites were isolated by using solvent extraction and repeated chromatographic methods and identified by using spectroscopic methods including UV, IR, mass spectrometry, NMR, and circular dichroism experiments. Four new compounds were identified as irisolidone-7-O-glucuronide (M-1), tectorigenin-7-O-sulfate (M-2), tectorigenin-4'-O-sulfate (M-3), and biochanin A-6-O-sulfate (M-4) together with nine known compounds identified as irisolidone (M-5), tectorigenin (M-6), tectoridin (M-7), 5,7-dihydroxy-8,4'-dimethoxyisoflavone (M-8), isotectorigenin (M-9), biochanin A (M-10), genistein (M-11), daidzein (M-12), and equol (M-13). The metabolic pathway of kakkalide was proposed, which is important to understand its metabolic fate and disposition in humans.