Previous studies reported multiple blood concentration peaks in the alkaloid PK and attributed it to the distribution, reabsorption, enterohepatic circulation or the administered drugs having been in a complex prescription [21], [22] and [23]. Other studies have demonstrated that TCMs and natural components from TCMs can be identified as inhibitors, substrates, and/or inducers of a variety of CYP enzymes, and TCMs-CYP interactions may occur and affect the pharmacokinetics [23]. The results also indicated that the absorption of the seven alkaloids and two phenolic acids might be rapid with the Tmax values within 2 h.
However, the Cmax of seven alkaloids was less than 20 ng mL−1. The AUC0−24 h values were 80.7 ± 9.89 ng mL−1 h−1 for berberine, 126 ± 19.6 ng mL−1 h−1 for coptisine, 48.2 ± 16.0 ng mL−1 h−1 for epiberberine, 37.9 ± 9.38 ng mL−1 h−1 for palmatine and 22.9 ± 6.24 ng mL−1 h−1 for jatrorrhizine. These showed that these alkaloids shared low plasma concentration. Previous studies concluded that the poor absorption and extensive metabolism might result in low plasma concentration of berberine after oral administration [23]. Because of their similar structures with berberine and lower contents for administration, the plasma concentration of the other four protoberberine-type alkaloids was lower. The values of T1/2 were in the range of 0.28–12.4 h, which were greatly different from previous study [23]. This was probably due to the different proportions of the components in JJT tablet and the individual differences in rats.