Isolation and identification of seven glucuronide conjugates of andrographolide in human urine

Andrographolide is one of the principal components of a famous traditional Chinese herbal medicine, Andrographis paniculate (Burm) Nees, and has been widely used in the clinic for the treatment of infectious diseases. In this paper, metabolites of andrographolide in the urine of eight healthy volunteers after oral administration were further investigated. Building on previous findings, an additional seven phase II metabolites were isolated by liquid-liquid extraction, open-column chromatography, medium-pressure liquid chromatography, and, finally, preparative high-performance liquid chromatography. Structural elucidation was carried out by mass spectra and NMR spectroscopy including H-1 NMR, C-13 NMR and two-dimensional NMR (distortionless enhancement by polarization transfer, heteronuclear multiple-quantum correlation, heteronuclear multiple-bond correlation, H-1-H-1 correlated spectroscopy, and nuclear Overhauser enhancement spectroscopy). All of the metabolites were characterized as glucuronide conjugates, and the structures were determined to be andrographolide-19-O-beta-D-glucuronide (M-1), isoandrographolide-19-O-beta-D-glucuronide (M-2), 14-deoxy-12-hydroxy-andrographolide-19-O-beta-D-glucuronide (M-3), andrographolide-19-O-[6'-methyl-beta-D-glucuronide] (M-4), 14-deoxy-12(13)-en-andrographolide-19-O-beta-D-glucuronide (M-5), 14-deoxyandrographolide-19-O-beta-D-glucuronide (M-6), and 3-oxoandrographolide-19-O-beta-D-glucuronide (M-7), respectively.