Effect of Honokiol on Cytochrome P450 and UDP-Glucuronosyltransferase Enzyme Activities in Human Liver Microsomes

Abstract

Honokiol is a bioactive component isolated from the medicinal herbs Magnolia officinalis and Magnolia grandiflora that has antioxidative, anti-inflammatory, antithrombotic, and antitumor activities. The inhibitory potentials of honokiol on eight major human cytochrome P450 (CYP) enzymes 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4, and four UDP-glucuronosyltransferases (UGTs) 1A1, 1A4, 1A9, and 2B7 in human liver microsomes were investigated using liquid chromatography-tandem mass spectrometry. Honokiol strongly inhibited CYP1A2-mediated phenacetin O-deethylation, CYP2C8-mediated amodiaquine N-deethylation, CYP2C9-mediated diclofenac 4-hydroxylation, CYP2C19-mediated [S]-mephenytoin 4-hydroxylation, and UGT1A9-mediated propofol glucuronidation with K i values of 1.2, 4.9, 0.54, 0.57, and 0.3 μM, respectively. Honokiol also moderately inhibited CYP2B6-mediated bupropion hydroxylation and CYP2D6-mediated bufuralol 1'-hydroxylation with K i values of 17.5 and 12.0 μM, respectively. These in vitro results indicate that honokiol has the potential to cause pharmacokinetic drug interactions with other co-administered drugs metabolized by CYP1A2, CYP2C8, CYP2C9, CYP2C19, and UGT1A9.

Inhibitory Effects of Aschantin on Cytochrome P450 and Uridine 5′-diphospho-glucuronosyltransferase Enzyme Activities in Human Liver Microsomes

“…Several medicinal herbs, including Allium sativum, Camellia sinensis, Ginkgo biloba, Glycyrrhiza glabra, Coptidis rhizoma, Silybi fructus, and St. John's wort are associated with herb-drug interactions attributable to inhibition and/or induction of drug-metabolizing enzymes [14][15][16][17]. Several lignans including honokiol [18], machilin A [19], magnolol [20], schizandrins [21], schizandrol B [22], phyllantin, hypophyllantin [23], and podophyllotoxin [24] cause herb-drug interactions featuring inhibition of CYP enzymes.…”

“…The incubation mixtures were prepared in total volumes of 100 µL, as follows: pooled human liver microsomes (0.2 mg/mL), 1.0 mM NADPH, 10 mM MgCl 2 , 50 mM potassium phosphate buffer (pH 7.4), various concentrations of aschantin in DMSO (final concentrations of 0.1-100 µM, DMSO less than 1% [v/v]), and a cocktail of seven CYP probe substrates as defined in our previous report [18]. The CYP substrates were used at concentrations approximating their respective K m values: 50 µM phenacetin, 2.5 µM coumarin, 2.0 µM amodiaquine, 10 µM diclofenac, 100 µM [S]-mephenytoin, 5 µM bufuralol, and 2.5 µM midazolam.…”

“…The metabolites formed from the seven substrates were simultaneously quantified using our previously described LC-MS/MS method [18]. To this end, we employed a tandem mass spectrometer (TSQ Quantum Access, Thermo Scientific, San Jose, CA, USA) coupled to a Nanospace SI-2 LC system (Shiseido, Tokyo, Japan).…”

“…The effects of aschantin on CYP2B6-catalyzed bupropion hydroxylase activity were evaluated using LC-MS/MS with pooled human liver microsomes [18]. Each incubation mixture was prepared in a total volume of 100 µL, including 1.0 mM NADPH, 10 mM MgCl 2 , 50 mM potassium phosphate buffer (pH 7.4), various concentrations of aschantin (0.1-100 µM), pooled human liver microsomes (0.2 mg/mL), and a CYP2B6-selective substrate (50 µM bupropion), as reported previously [18].…”

“…Each incubation mixture was prepared in a total volume of 100 µL, including 1.0 mM NADPH, 10 mM MgCl 2 , 50 mM potassium phosphate buffer (pH 7.4), various concentrations of aschantin (0.1-100 µM), pooled human liver microsomes (0.2 mg/mL), and a CYP2B6-selective substrate (50 µM bupropion), as reported previously [18]. After 3 min of pre-incubation at 37˝C, each reaction was initiated by adding NADPH; incubation proceeded for 15 min at 37˝C in a shaking water bath.…”