Human Cytochrome P450 Inhibition and Metabolic-Intermediate Complex Formation by Goldenseal Extract and Its Methylenedioxyphenyl Components

Abstract

This article is available online at http://dmd.aspetjournals.org ABSTRACT:The concurrent use of herbal medicinals with prescription and over-the-counter drugs carries a risk for unanticipated adverse drug-botanical pharmacokinetic interactions, particularly as a result of cytochrome P450 (P450) inhibition. Extracts of goldenseal (Hydrastis canadensis) containing approximately equal concentrations (ϳ17 mM) of two methylenedioxyphenyl alkaloids, berberine and hydrastine, inhibited with increasing potency (CYP2C9) diclofenac 4-hydroxylation, (CYP2D6) bufuralol 1-hydroxylation, and (CYP3A4) testosterone 6␤-hydroxylation activities in human hepatic microsomes. The inhibition of testosterone 6␤-hydroxylation activity was noncompetitive with an apparent K i of 0.11% extract. Of the methylenedioxyphenyl alkaloids, berberine (IC 50 ‫؍‬ 45 M) was the more inhibitory toward bufuralol 1-hydroxylation and hydrastine (IC 50 ϳ350 M for both isomers), toward diclofenac 4-hydroxylation. For testosterone 6␤-hydroxylation, berberine was the least inhibitory component (IC 50 ϳ400 M). Phytomedicinals are being used concomitantly with conventional prescription or over-the-counter drugs, a situation that carries the risk of unanticipated adverse drug-botanical pharmacokinetic interactions. A likely important locus of interactions is phase I drug metabolism, where alterations by both inhibition and induction can occur. Goldenseal (Hydrastis canadensis) is a popular immunostimulant, and goldenseal-containing herbal supplements rank high among botanical products sold (Eisenberg at al., 1998). Goldenseal extract contains isoquinoline alkaloids, including berberine, (ϩ)-and (Ϫ)-hydrastine, and lesser amounts of hydrastinine (Fig. 1). Chemically, these three goldenseal alkaloids possess a methylenedioxyphenyl (MDP 1 ) moiety which, in studies of cytochrome P450 (P450)-dependent drug metabolism, frequently give rise to inhibition. The inhibition often shows complex inhibition kinetics (Franklin, 1972). The complexity arises from the ability of the methylenic carbon in MDPs to undergo oxidization to a carbene, which then interacts with the heme iron of cytochrome P450 to produce a stable heme-adduct termed a cytochrome P450 metabolic-intermediate (MI) complex (Franklin, 1971;Philpot and Hodgson, 1971). Inhibition by P450 MI complexes is best characterized as "quasi-irreversible" (Ortiz de Montellano and Reich, 1986). The methylenedioxyphenyl P450 MI complexes show pH dependent dual absorbance maxima around 455 and 430 nm (Hodgson et al., 1973) with the former being the more readily identifiable at pH 7.4 (Franklin, 1971). Most investigations with P450 MI complex formation have been undertaken using laboratory animal liver microsomes; little has been undertaken using human enzymes. A recent report (Mathews et al., 2002) has recorded that methysticin and dihydromethysticin, two MDP components of kava extract, are able to form a P450 MI complex in human hepatic microsomes. P450 MI complex formation with goldenseal MDP components has not been rep...

Effect of Goldenseal (Hydrastis canadensis) and Kava Kava (Piper methysticum) Supplementation on Digoxin Pharmacokinetics in Humans

“…Evidently, the concentration of certain goldenseal components is sufficient to inactivate these enzymes in vivo. This inactivation by goldenseal likely stems from the formation of a stable heme adduct between the methylenedioxyphenyl moiety of berberine and hydrastine and the heme iron of the enzyme (Chatterjee and Franklin, 2003). Interestingly, two kavalactones, methysticin and dihydromethysticin, are also substituted methylenedioxyphenyl compounds, yet they do not inhibit CYP3A4 or CYP2D6 in vivo.…”

Computational Approaches That Predict Metabolic Intermediate Complex Formation with CYP3A4 (+b5)

“…These approaches may be equally applicable to naturally occurring compounds as well as to drugs. The modeling methods could also be applied to other P450s that are known to form MIC (Chatterjee and Franklin, 2003), such as CYP3A5 and CYP2D6, enabling a comparison with the CYP3A4 data presented herein, providing insight into the features important for MIC formation, and representing a more complete picture for pharmaceutical research.…”

“…Pharmacophore, tree models, and the logistic regression model were tested with molecules outside of the training set using recently published data for 12 compounds (Yamazaki and Shimada, 1998;Kasahara et al, 2000;Kim et al, 2001;Kajita et al, 2002;Chatterjee and Franklin, 2003;Wu et al, 2003) with MIC formation for CYP3A4.…”

The Interaction of Selected Phytochemicals, HIV Drugs, and Commercial-Source Herbal Teas and Capsules with Human Cytochrome P450 3A4 and P-glycoprotein

“…These assays allow researchers to broadly screen numerous NHP species, NHP formulations, phytochemicals, drugs, and so forth, in a high-throughput manner, thereby allowing them to target specific products to be advanced to more detailed in vitro and/or in vivo animal testing, and ultimately more informative but costly human preclinical and clinical trials. In this study, it was initially hypothesized that extracts from commercial-source goldenseal and milk thistle NHPs would be highly active in both in vitro assays because these plants are known to have constituents that are both inhibitory of CYP3A4-mediated metabolism and are substrates for P-gp transport (Budzinski et al, 2000;Maitrejean et al, 2000;Stermitz et al, 2000;Venkataramanan et al, 2000;Chatterjee & Franklin, 2003). The results of this study showed that aqueous extracts of goldenseal (NRP 17 and NRP 121) were more inhibitory of CYP3A4, with the lowest IC 50 values among all NHPs tested (ranging from 3.03 to 3.23 mg/mL).…”