Cytochrome P450 inhibition by three licorice species and fourteen licorice constituents

Abstract

The potential of licorice dietary supplements to interact with drug metabolism was evaluated by testing extracts of three botanically identified licorice species (Glycyrrhiza glabra L., Glycyrrhiza uralensis Fish. ex DC. and Glycyrrhiza inflata Batalin) and 14 isolated licorice compounds for inhibition of 9 cytochrome P450 enzymes using a UHPLC-MS/MS cocktail assay. G. glabra showed moderate inhibitory effects against CYP2B6, CYP2C8, CYP2C9, and CYP2C19, and weak inhibition against CYP3A4 (testosterone). In contrast, G. uralensis strongly inhibited CYP2B6 and moderately inhibited CYP2C8, CYP2C9 and CYP2C19, and G. inflata strongly inhibited CYP2C enzymes and moderately inhibited CYP1A2, CYP2B6, CYP2D6, and CYP3A4 (midazolam). The licorice compounds isoliquiritigenin, licoricidin, licochalcone A, 18β-glycyrrhetinic acid, and glycycoumarin inhibited one or more members of the CYP2C family of enzymes. Glycycoumarin and licochalcone A inhibited CYP1A2, but only glycycoumarin inhibited CYP2B6. Isoliquiritigenin, glabridin and licoricidin competitively inhibited CYP3A4, while licochalcone A (specific to G. inflata roots) was a mechanism-based inhibitor. The three licorice species commonly used in botanical dietary supplements have varying potential for drug-botanical interactions as inhibitors of cytochrome P450 isoforms. Each species of licorice displays a unique profile of constituents with potential for drug interactions.

Fig. 1

Chemical structures of the 14 licorice compounds tested individually for inhibition of cytochrome P450 enzymes.

Fig. 2

Inhibition curves for the inhibition of cytochrome P450 enzymes by extracts G. uralensis, G. inflata and G. glabra obtained using a cocktail assay. Activity is expressed as a percentage of remaining activity compared with the control containing no inhibitor. Experiments were carried out three times.

Fig. 3

Inhibition of CYP enzymes by isoliquiritigenin, glabridin, glycyrrhetinic acid, licoricidin, glycycoumarin, and licochalcone A at 10 µM. Activity is expressed as a percentage of remaining activity compared with the control containing no inhibitor. Experiments were carried out in duplicate. 3AM: CYP3A4 (midazolam); 3AT: CYP3A4 (testosterone).

Fig. 4

Determination of K_I and k_inact for inactivation of CYP3A4 (midazolam) by licochalcone A. (A) Time- and concentration-dependent inactivation of CYP3A4 (midazolam) by licochalcone A. (B) Non-linear regression analysis of k_obs,app. Activity is expressed as a percentage of remaining activity compared with the control containing no inhibitor. Experiments were carried out three times.

Fig. 5

Determination of K_I and k_inact for inactivation of recombinant CYP3A4 (midazolam) by licochalcone A. (A) Time- and concentration-dependent inactivation of recombinant CYP3A4 (midazolam) by licochalcone A. (B) Non-linear regression analysis of k_obs,app. Activity is expressed as a percentage of remaining activity compared with the control containing no inhibitor. Experiments were carried out three times.