Identification and analysis of absorbed and metabolic components in rat plasma after oral administration of ‘Shuangdan’ granule by HPLC–DAD–ESI-MS/MS

A valid method using liquid chromatography–diode array detection–electrospray ionization (ESI) ion trap mass spectrometry was established for the study of the absorbed and metabolic components of a Chinese medicine ‘Shuangdan’ granule in rat plasma after oral administration. The plasma samples were acidified with 1 M hydrochloric acid and extracted with ethyl acetate (EtOAc) of two-fold volume for three times. The chromatographic separation was carried out on a Zorbax SB-C18 column with a linear gradient whereas 0.1% acetic acid/water/acetonitrile was used as mobile phase. Mass spectra were acquired in both negative and positive modes. More than 20 components including 16 components from ‘Shuangdan’ granule and 5 metabolites were simultaneously identified by comparing their mass spectra and retention behavior with reference compounds or literature data. The results proved that the established method could be used to identify the structure of active components responsible for the pharmacological effects of ‘Shuangdan’ granule.