Simultaneous Determination of Silibinin A and Silibinin B in Rat Plasma and Pharmacokinetic Study

Objective To investigate the bioavailability and pharmacokinetics of silibinin A and silibinin B in rats, respectively. Methods Following iv and ig administration of silibinin to 20 Wistar rats, the plasma samples were collected at different time points up to 12 h. Sample pretreatment was involved in one-step protein precipitation with acetonitrile. Silibinin A and silibinin B were simultaneously determined by LC-MS/MS. Results After ig dosing silibinin 28, 56, and 112 mg/kg to rats, the t1/2β values were 5.48, 5.08, and 5.73 h for silibinin A, and 4.56, 4.12, and 5.53 h for silibinin B; The Cmax were 674.3, 1349.4, and 2042.5 ng/mL for silibinin A, and 671.0, 1365.4, and 2066.2 ng/mL for silibinin B; The Tmax were 0.20, 0.23, and 0.20 h for silibinin A, and 0.20, 0.23, and 0.20 h for silibinin B; The AUC were 454.4, 845.9, and 1219.5 h·ng/mL for silibinin A, and 432.0, 817.1, and 1153.6 h·ng/mL for silibinin B. The absolute bioavailabilities of silibinin A and silibinin B were 2.86% and 1.93%, respectively. Conclusion Silibinin A and silibinin B have very low bioavailability after ig administration, and there is no significant difference in the pharmacokinetic parameters between silibinin A and silibinin B, which indicates that the two diastereoisomers have similar pharmacokinetic behavior in rats.