Comparative pharmacokinetics, intestinal absorption and urinary excretion of six alkaloids from herb pair Phellodendri Chinensis cortex–Atractylodis Rhizoma

Abstract Phellodendri Chinensis Cortex (PCC) and Atractylodis Rhizoma (AR) are frequently used as herb pair to treat eczema and gout owing to their synergistic effects. Alkaloids are the major ingredients from PCC and the effect of their combination on the in vivo processing of alkaloids remains unclear. In this study, a simple and reliable UPLC–MS/MS method for simultaneous determination of six alkaloids in rat plasma was developed. This method was applied to a comparative pharmacokinetic study between PCC and PCC–AR in rats. Effect of AR on absorption of alkaloids was investigated by a single‐pass intestinal perfusion study. The effect of AR on urinary excretion of alkaloids was studied. Pharmacokinetic studies showed that the values of rea under the concentration–time curve of phellodendrine, magnoflorine and palmatine were greater in the PCC–AR group than in the PCC group. The intestinal absorptive parameters absorption rate constant and effective permeability of phellodendrine and jatrorrhizine in PCC–AR groups were higher than those in the PCC group. Urinary excretion studies revealed that the excreted amount of alkaloids in the PCC–AR group was lower than that in the PCC group. The results revealed that the combination of PCC and AR improves intestinal absorption of alkaloids and reduces their urinary excretion, which enhances their systemic exposure. This study may explain the synergetic effects of PCC and AR in clinical applications.