Guanfu base A is an antiarrhythmic alkaloid isolated from Aconitum coreanum and is a potent noncompetitive CYP2D6 inhibitor, with a Ki of 1.20 μM in human liver microsomes (HLMs) and a Ki of 0.37 μM for the human recombinant form (rCYP2D6). Guanfu base A is also a potent competitive inhibitor of CYP2D in monkey (Ki of 0.38 μM) and dog (Ki of 2.4 μM) microsomes[1]. Guanfu base A also inhibits HERG channel current[2].
Guanfu base A has no inhibitory activity on mouse or rat CYP2Ds. Guanfu base A does not exhibit any inhibition activity on human recombinant CYP1A2, 2A6, 2C8, 2C19, 3A4, or 3A5, but shows slight inhibition of 2B6 and 2E1[1].Guanfu base A is a potent inhibitor of CYP2D6, with an IC50 recorded at ~0.46 μM in HLM (Dextromethorphan 5 μM) and 0.12 μM in rCYP2D6 (Bufuralol 5 μM)[1]. The effects of Guanfu base A is investigated in human embryonic kidney 293 (HEK293) cells transiently transfected with HERG complementary DNA using a whole-cell patch clamp technique. Guanfu base A inhibits HERG channel current in concentration-, voltage-, and time-dependent manners with an IC50 of 1.64 mM. Guanfu base A shifts the activation curve in a negative direction and accelerated channel inactivation but shows no effect on the inactivation curve[2].
Beagle dogs treated intravenously with Dextromethorphan (2 mg/mL) after pretreatment with Guanfu base A injection shows reduced CYP2D metabolic activity, with the Cmax of dextrorphan being one-third that of the saline-treated group and area under the plasma concentration-time curve half that of the saline-treated group[1].
[1]. Sun J, et al. Guanfu base A, an antiarrhythmic alkaloid of Aconitum coreanum, Is a CYP2D6 inhibitor of human, monkey, and dog isoforms. Drug Metab Dispos. 2015 May;43(5):713-24.
[2]. Huang X, et al. Comparative effects of Guanfu base A and Guanfu base G on HERG K+ channel. J Cardiovasc Pharmacol. 2012 Jan;59(1):77-83.