The aim of this paper was to investigate the absorption mechanism of silybin(SLB)in Caco-2 cells. Concentrations of samples in the study were determined by developing LC/MS/MS method of SLB, propranolol and atenolol in HBSS buffer to calculate apparent permeability coefficient(Papp). When Caco-2 cells were cultured to the 21st day, the TEER were above 350 Ω ·cm2. The Papp of Lucifer yellow was far less than 1 × 10-7 cm/s. As the positive control drugs, The Papp of atenolol and propranolol were similar to those reported in the literature, indicating that the Caco-2 monolayer model was successfully established in this experiment. The Papp(AP-BL) of SLB at 5, 20, and 50 μg/mL were all more than 2×10-6 cm/s, which showed that SLB was a moderately permeable drug. The efflux ratio was greater than 2 indicating the efflux transporter may be involved in the absorption process of SLB. The Papp of silybin-N-meglumine was similar to that of SLB, suggesting that salt formation did not alter the membrane permeability of SLB. In conclusion, the membrane permeability of SLB is good, and its solubility is low. SLB is a BCS class 2 drug. The release of SLB in the gastrointestinal tract is an important factor in its absorption process.

To investigate the effect of combination of schisandrin B and doxorubicin on the pharmacokinetic behavior of doxorubicin in SD rats. An LC-MS/MS method was established for the determination of doxorubicin and its main metabolite doxorubicinol in SD rats plasma. Separation was performed on Agilent Eclipse XDB-C18 column(100 mm×2. 1 mm, 3. 5 μm)using 0. 1% formic acid solution and acetonitrile as mobile phase with a liner gradient program. The ion transitions were performed under ESI position model at m/z 544. 2→397. 3(doxorubicin), m/z 546. 2→399. 2(doxorubicinol), m/z 528. 2→381. 2(daunorubicin, internal standard). Calibration curves of doxorubicin(0. 500-500 ng/mL)and doxorubicinol(0. 200-50. 0 ng/mL)showed good linear regression. The precision and accuracy met the requirements. The variation coefficient of extraction recovery and matrix effect was less than 15%. The AUC0-t of doxorubicin were(605. 69±145. 84)and(564. 53±23. 99)ng ·h/mL in alone and combined group, respectively. The AUC0-t of doxorubicinol were(26. 69±13. 41)and(29. 00±2. 78)ng ·h/mL, respectively. Results indicated that, schisandrin B had not affected the pharmacokinetic behavior of doxorubicin in SD rats.