Kinase experiment:

For the determination of the inhibition constant Ki values, various final concentrations of the specific substrate dextromethorphan for CYP2D6 in the range of 1 to 10 mM and different concentrations of the N-Nornuciferine in the range of 0 to 25 mM are used. After preincubation for 10 min, the reactions are initiated by the addition of NADPH. Each incubation test is performed in triplicate. Thirty minutes after the incubation is initiated, the reaction is stopped by the addition of 100 mL of ice-cold acetonitrile containing 1 mg/mL propranolol (IS). The incubation mixtures are then centrifuged at 15,000g for 10 min at 4 ℃. Ten-microliter aliquots of the supernatants are injected into an LC-MS/MS system[1].

N-Nornuciferine is an aporphine alkaloid in lotus leaf that significantly inhibits CYP2D6 with IC50 and Ki of 3.76 and 2.34 μM, respectively. IC50: 3.76 μM (CYP2D6)[1]Ki: 2.34 μM (CYP2D6)[1]

The herb of lotus leaves is a commonly used traditional Chinese medicine with a wide range of pharmacological and physiological activities, particularly the reduction of the blood triglyceride and cholesterol levels. N-Nornuciferine strongly inhibits CYP2D6 activity but shows weak or no inhibition of the other four P450 isoenzymes (CYP2C19, CYP3A4, CYP2E1, CYP2C9). N-Nornuciferine competitively inhibits the CYP2D6-catalyzed dextromethorphan o-demethylation with apparent Ki values of 2.34 μM[1].

[1]. Ye LH, et al. Identification and characterization of potent CYP2D6 inhibitors in lotus leaves. J Ethnopharmacol. 2014 Apr 11;153(1):190-6.