Development of an UHPLC-MS/MS method for comparative pharmacokinetics of nine anthraquinones in rats and application to dosage conversion between different Semen Cassiae forms.

Semen Cassiae, called Juemingzi in Chinese, is widely used in clinic for alleviating constipation, improving eyesight and preventing hyperlipidemia. It can be used as medicine or food including many application forms, such as traditional pieces and ultrafine granular powder (UGP). In this paper, comparative pharmacokinetics of Semen Cassiae in different forms of traditional pieces and UGP were achieved to research the clinical dosage of UGP. Also, the scientific connotation of brewing way for traditional pieces of Semen Cassiae application in clinic was revealed. To achieve this purpose, a rapid, sensitive and reliable UHPLC-MS/MS method was developed for simultaneous determination of rhein, emodin, aloe-emodin, chrysophanol, physcion, aurantio-obtusin, chryso-obtusin, obtusifolin and obtusin in rat plasma. Multiple reaction monitoring mode via an electrospray ionization was applied for the quantitation of the analytes. The separation was carried out on an Agilent Extend-C₁₈ column (100 mm × 2.1 mm, 1.8 μm) with an 8.0 min gradient elution using ultra-purify water and acetonitrile as mobile phase. The samples were prepared by liquid-liquid extraction with ethyl acetate. The development and validation of bioanalytical method were performed according to the latest "Bioanalytical Method Validation: Guidance for Industry" issued by FDA in 2018. Finally, the clinical dosage of UGP was concluded to be 1/4 of Semen Cassiae traditional pieces in oral administration way by comparing the pharmacokinetic parameters of UGP to that of traditional pieces in the aspect of mathematical statics using plus of AUC values.