Abstract:The tuber of Corydalis yanhusuo is a famous traditional Chinese medicine and found to have potent pharmacological effects, such as antinociceptive, antitumor, antibacterial, anti-inflammatory, and anti-depressive activities. Although there are several methods to be developed for the analysis and detection of the bioactive ingredients' alkaloids, so far, only few prominent alkaloids could be quantified, and in vitro and in vivo changes of comprehensive alkaloids after oral administration are still little known. In this study, we first developed a simple and sensitive high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method to quantify the comprehensive alkaloids of extracts of C. yanhusuo in mouse plasma, using nitidine chloride as an internal standard. As results, at least fourteen alkaloids, including an aporphine (oxoglaucine), a protopine (protopine), five tertiary alkaloids (corydaline, tetrahydroberberine, tetrahydropalmatine, tetrahydrocolumbamine, and tetrahydrocoptisine) and seven quaternary alkaloids (columbamine, palmatine, berberine, epiberberine, coptisine, jatrorrhizine, and dehydrocorydaline) could be well quantified simultaneously in mouse plasma. The lower limits of quantification were greater than, or equal to, 0.67 ng/mL, and the average matrix effects ranged from 96.4% to 114.3%. The mean extraction recoveries of quality control samples were over 71.40%, and the precision and accuracy were within the acceptable limits. All the analytes were shown to be stable under different storage conditions. Then the established method was successfully applied to investigate the pharmacokinetics of these alkaloids after oral administration of the extract of Corydalis yanhusuo in mice. To the best of our knowledge, this is the first document to report the comprehensive and simultaneous analyses of alkaloids of C. yanhusuo in mouse plasma. It was efficient and useful for comprehensive pharmacokinetic and metabolomic analyses of these complex alkaloids after drug administration.

Dehydrocorydaline (DHC), one of the main active components of Corydalis yanhusuo, is an important remedy for the treatment of coronary heart disease. Our previous study revealed a higher unbound concentration of DHC in the heart than plasma of mice after oral administration of C. yanhusuo extract or DHC, but the underlying uptake mechanism remains unelucidated. In our investigations, we studied the transport mechanism of DHC in transgenic cells, primary neonatal rat cardiomyocytes, and animal experiments. Using quantitative real-time polymerase chain reaction and Western blotting, we found that uptake transporters expressed in the mouse heart include organic cation transporter 1/3 (OCT1/3) and carnitine/ organic cation transporter 1/2 (OCTN1/2). The accumulation experiments in transfected cells showed that DHC was a substrate of OCT1 and OCT3, with K m of 11.29 6 3.3 and 8.96 6 3.7 mM, respectively, but not a substrate of OCTN1/2. Additionally, a higher efflux level (1.71-fold of MDCK-mock) of DHC was observed in MDCK-MDR1 cells than in MDCK-mock cells. Therefore, DHC is a weak substrate for MDR1. Studies using primary neonatal rat cardiomyocytes showed that OCT1/3 inhibitors (quinidine, decynium-22, and levo-tetrahydropalmatine) prevented the accumulation of DHC, whereas OCTN2 inhibitors (mildronate and l-carnitine) did not affect its accumulation. Moreover, the coadministration of OCT1/3 inhibitors (levo-tetrahydropalmatine, THP) decreased the concentration of DHC in the mouse heart. Based on these findings, DHC may be accumulated partly by OCT1/3 transporters and excreted by MDR1 in the heart. THP could alter the distribution of DHC in the mouse heart. SIGNIFICANCE STATEMENTWe reported the cardiac transport mechanism of dehydrocorydaline, highly distributed to the heart after oral administration of Corydalis yanhusuo extract or dehydrocorydaline only. Dehydrocorydaline (an OCT1/3 and MDR1 substrate) accumulation in primary cardiomyocytes may be related to the transport activity of OCT1/3. This ability, hampered by selective inhibitors (levo-tetrahydropalmatine, an inhibitor of OCT1/3), causes a nearly 40% reduction in exposure of the heart to dehydrocorydaline. These results suggest that OCT1/3 may contribute to the uptake of dehydrocorydaline in the heart.

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Nuciferine (NF), one of the main and effective components in Nelumbo nucifera Gaertn. leaf extracts, is a promising drug candidate for the treatment of obesity‐related diseases, while metformin is a first line therapeutic drug for type 2 diabetes mellitus. Since nuciferine and metformin are likely to be co‐administered, the aim of the present study was to evaluate whether co‐administration of nuciferine would influence the liver (target tissue) distribution and the anti‐diabetic effect of metformin by inhibiting hepatic organic cation transporter 1 (OCT1) and multidrug and toxin extrusion 1 (MATE1). The data demonstrated that nuciferine significantly reduced metformin accumulation in MDCK cells stably expressing human OCT1 (MDCK‐hOCT1) or hMATE1 (MDCK‐hMATE1), and primary cultured mouse hepatocytes. Furthermore, the presence of nuciferine in the basal compartment caused a concentration‐dependent reduction of intracellular metformin accumulation in MDCK‐hOCT1/hMATE1 cell monolayers. Compared with the metformin treatment‐alone group, co‐administration of nuciferine (40 mg/kg) markedly reduced the metformin concentration in mouse livers at 30 and 60 min after a single oral dose of metformin (200 mg/kg), and subsequently impaired the glucose‐lowering effect of metformin (200 mg/kg), but the glucose‐lowering effect became no different at 90 and 120 min. Therefore, nuciferine influenced the liver concentration and glucose‐lowering effect of metformin only for a period of time after dose, administration of nuciferine and metformin with an interval might prevent the drug–drug interaction mediated by OCT1 and MATE1.

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