Identification of metabolites of Danggui Buxue Tang in rat urine by liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry.

A method coupling liquid chromatography with electrospray ionization time-of-flight mass spectrometry (LC/ESI-TOF/MS) has been developed for rapid and sensitive analysis of rat urinary metabolite profile of Danggui Buxue Tang (DBT), a well-known Chinese herbal formula. After oral administration of DBT, urine samples were collected during 0-24 h, and then pretreated by solid-phase extraction. A total of 68 compounds including 13 parent compounds and 55 metabolites were detected in the drug-containing urines compared with blank urines. The total analytical time was less than 20 min. Metabolites of DBT were identified using dynamic adjustment of the fragmentor voltage to produce structure-relevant fragment ions. By using this approach, the mass accuracy of precursor and fragment ions was typically within +/-5 ppm of the theoretical values, and enabled the identification of 43 metabolites including 27 isoflavanoid and 16 phthalide metabolites. Our results indicated that glucuronidation and sulfation were the major metabolic pathways of isoflavonoids, while glutathione conjugation, glucuronidation and sulfation were the main metabolic pathways of phthalides. No saponin-related metabolites were detected. The results of the present study provided important structural information relating to the metabolism of DBT. Furthermore, this work demonstrated the potential of the LC/ESI-TOF/MS approach for identification of metabolites from Chinese herbal medicines in urine.