A sensitive and specific HPLC-MS method for the determination of sophoridine, sophocarpine and matrine in rabbit plasma.

A sensitive and specific method was developed for the determination of sophoridine (SRI), sophocarpine (SC) and matrine (MT) in rabbit plasma by HPLC-MS. After an administration of Kuhuang by injection, blood samples were collected and extracted with methanol. The extract solutions were analysed by HPLC-MS method. The separation was performed on a ZORBAX Extend-C18 column using methanol/water/diethylamine (50:50:0.07, v/v/v) as mobile phase. The quinolizidine alkaloids were detected by using mass spectrometry in the SIM mode. There was a good linear relationship between peak area and concentration of analytes over the concentration range of 13.2-995.0 ng mL(-1) for SRI, 7.0-530.0 ng mL(-1) for SC and 8.8-655.0 ng mL(-1) for MT, respectively. The absolute recovery of this method was more than 57% for SRI, 87% for SC and 91% for MT. The accuracy of assay was more than 90%. The limits of detection (LODs) were 6.8 ng mL(-1) for SRI, 3.5 ng mL(-1) for SC and 4.2 ng mL(-1) for MT, respectively. The limits of quantitation (LOQs) were 13.2 ng mL(-1) for SRI, 7.0 ng mL(-1) for SC and 8.8 ng mL(-1) for MT, respectively. The intra-day and inter-day coefficients of variation (RSDs) were less than 10.1, 6.3 and 5.8% for SRI, SC and MT, respectively. The developed method was applied to determine the concentration-time profiles of SRI, SC and MT in rabbit plasma after injection of Kuhuang.