Purpose: The coadministation of Panax ginseng and Veratrum nigrum L. is forbidden in Traditional Chinese Medicine Therapy. However, the mechanism is not clear. This study aims to investigate the herb-herb interactions based on the pharmacokinetics of major active ingredients of Panax ginseng and Veratrum nigrum L. in Sprague-Dawley rats and to estimate the modulations of P450s activities in Sprague-Dawley rats after the coadministration of Panax ginseng and Veratrum nigrum L.. The gender-dependent herb-herb interactions are evaluated in this study.
Methods: An UPLC-MS method was developed to simultaneously determine ginsenoside-Rb1, Rc, Rd, Re, Rf, Rg1 (the major ingredients in Panax ginseng) and veratramine (the major toxic ingredient in Veratrum nigrum L.) in rat plasma. Extracts of Panax ginseng and Veratrum nigrum L. were orally administrated to male and female rats in four groups (blank group, Panax ginseng group, Veratrum nigrum L. group, and the combination group of Panax ginseng and Veratrum nigrum L.). Plasma samples were collected at the different time intervals and analyzed using the developed UPLC-MS method. The pharmacokinetic parameters were calculated by KineticaTM and compared among groups. Furthermore, in-vivo cocktail assay was performed to evaluate the modulations of P450s activities (CYP2C, CYP2D and CYP3A) in rats after coadministration of Panax ginseng and Veratrum nigrum L.. Cocktail substrates (S-mephenytoin, dextromethorphan and midazolam) were administrated to rats after the 7-day successive administration of herbal extracts in four groups (described above). The cumulative amount of the metabolite or the ratio of the metabolite’s concentration versus the parent compound’s concentration was used to evaluate the catalytic activities of P450s in vivo. The modulations of P450s activities were compared among groups.
Results: A validated UPLC-MS method was developed with satisfactory sensitivity, selectivity, accuracy, precision, recovery, matrix effect and stability for the quantitative measurement of ginsenoside-Rb1, Rc, Rd, Re, Rf, Rg1 and veratramine in rat plasma. Ginsenoside-Rb1, Rc, Rd, Rg1 and veratramine were determined in rat plasma after oral administration of Panax ginseng and Veratrum nigrum L.. In comparison to the Panax ginseng group, coadministration of Panax ginseng and Veratrum nigrum L. significantly decreased the Cmax (662.67±219.03 vs. 257.25±122.25 ng/mL) and AUC (1136.05±269.27 vs. 522.33±284.60 min*μg/mL) and increased the CL ((3.04±0.71)E-05 vs. (8.40±4.88)E-05 mL/min) of ginsenoside-Rd in male rats, and no gender difference on the pharmacokinetic parameters of ginsenoside-Rd between the Panax ginseng group and the combination group was observed. Additionally, in comparison to the Veratrum nigrum L. group, the Cmax (24.71±6.10 vs. 53.46±14.86 ng/mL) and AUC (22.15±8.95 vs. 44.89±13.96 min*μg/mL) of veratramine were significantly increased in the combination group in male rats. However, trace amount of veratramine was determined without significant difference between Veratrum nigrum L. group and the combination group in female rats. It was proved that the metabolism of veratramine was much higher in female rats than that in male rats due to the female-predominant expression of SULT2A in our study, leading to the trace amount of veratramine determined in female rats. In addition, the catalytic activities of CYP2C, CYP2D and CYP3A were not significantly induced or inhibited in Panax ginseng group or Veratrum nigrum L. group. However, the catalytic activity of CYP2D was significantly inhibited in the combination group. It was also proved that CYP2D was the major enzyme for the metabolism of veratamine in our study.
Conclusion: In comparison to single herb group, coadministration of Panax ginseng and Veratrum nigrum L. led to a decrease on the exposure of the active ingredient in Panax ginseng (ginsenoside-Rd) in male and female rats, and an increase on the exposure of the toxic ingredient in Veratrum nigrum L. (veratramine) only in male rats. Furthermore, the catalytic activity of CYP2D was significantly decreased in the combination group in rats. Thus, the gender-dependent herb-herb interactions between Panax ginseng and Veratrum nigrum L. were preliminarily elucidated in this study.
Wenbin Zhou– Shanghai Zhulian Intelligent Technology Co., Ltd., Shanghai
Fang Kou– Shanghai University of Traditional Chinese Medicine, Shanghai
Ning Zhang– Shanghai University of Traditional Chinese Medicine, Shanghai
Hai Wei– Shanghai University of Traditional Chinese Medicine, Shanghai