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...
Microbial transformation of the antimelanoma agent betulinic acid was studied. The main objective of this study was to utilize microorganisms as in vitro models to predict and prepare potential mammalian metabolites of this compound. Preparative-scale biotransformation with resting-cell suspensions of Bacillus megaterium ATCC 13368 resulted in the production of four metabolites, which were identified as 3-oxo-lup-20(29)-en-28-oic acid, 3-oxo-11␣-hydroxy-lup-20(29)-en-28-oic acid, 1-hydroxy-3-oxo-lup-20(29)-en-28-oic acid, and 3,7,15␣-trihydroxy-lup-20(29)-en-28-oic acid based on nuclear magnetic resonance and high-resolution mass spectral analyses. In addition, the antimelanoma activities of these metabolites were evaluated with two human melanoma cell lines, Mel-1 (lymph node) and Mel-2 (pleural fluid).Betulinic acid (compound 1, Fig. 1), 3-hydroxy-lup-20(29)-en-28-oic acid, is a pentacyclic lupane type of triterpene that is widely distributed in the plant kingdom (8,19). Betulinic acid has been shown to exhibit a variety of biological activities, including inhibition of human immunodeficiency virus (HIV) replication in H9 lymphocyte cells (11), blockage of HIV type 1 entry into cells (20), and inhibition of DNA polymerase  (18). Synthetic derivatives of betulinic acid have also been investigated as specific inhibitors of HIV type 1 (11-13). In addition, betulinic acid has been reported to be a melanomaspecific cytotoxic agent in both in vitro cell culture and in vivo studies (24). The antitumor activity of this compound is mediated by the induction of apoptosis, as demonstrated by a variety of cellular responses (24). Due to its high level of antitumor activity and lack of toxicity, betulinic acid is an attractive and promising new lead compound for use against human melanoma and is currently undergoing preclinical development for treatment or prevention of malignant melanoma.An essential part of the preclinical development of a drug is elucidation of its mammalian metabolism. Since there have been no reports on the mammalian metabolism of betulinic acid, a prospective approach was used to study its metabolism by utilizing microorganisms as in vitro model systems. Fungi, bacteria, and yeasts have been utilized successfully as in vitro models to mimic and predict the metabolic fate of drugs and other xenobiotics in mammalian systems (7,9,15,16,28). Studies have shown that many of the mammalian phase I and phase II biotransformation reactions, including hydroxylation, N oxidation, O and N dealkylation, dehydrogenation, and glucuronide and sulfate conjugation reactions, occur in microbial systems as well (27). The biochemical bases for this parallelism in metabolic reactions lie in the similarity between mammalian and microbial enzyme systems, such as cytochrome P450 monooxygenases and copper oxidases. These studies, which have been extensively reviewed in the literature, highlighted the potential value of microbial transformations as a powerful tool for mimicking and predicting mammalian biotransformations ...
Microbial transformation of the antimelanoma agent betulinic acid (1) was studied. Preparative scale biotransformation with resting-cell suspensions of Cunninghamella species NRRL 5695 resulted in the production of a fungal metabolite of 1, which has been characterized as 28-O-beta-D-glucopyranosyl 3beta-hydroxy-lup-20(29)-en-28-oate (2) based on spectral and enzymic data. The in vitro cytotoxicity assay of metabolite 2 revealed no activity against several human melanoma cell lines.
Microbial transformation studies of the antimelanoma agent betulinic acid (1) were conducted. Screening experiments showed a number of microorganisms capable of biotransforming 1. Three of these cultures, Bacillus megaterium ATCC 14581, Cunninghamella elegans ATCC 9244, and Mucor mucedo UI-4605, were selected for preparative scale transformation. Bioconversion of 1 with resting-cell suspensions of phenobarbital-induced B. megaterium ATCC 14581 resulted in the production of the known betulonic acid (2) and two new metabolites: 3beta,7beta-dihydroxy-lup-20(29)-en-28-oic acid (3) and 3beta,6alpha, 7beta-trihydroxy-lup-20(29)-en-28-oic acid (4). Biotransformation of 1 with growing cultures of C. elegans ATCC 9244 produced one new metabolite characterized as 1beta,3beta, 7beta-trihydroxy-lup-20(29)-en-28-oic acid (5). Incubation of 1 with growing cultures of M. mucedo UI-4605 afforded metabolite 3. Structure elucidation of all metabolites was based on NMR and HRMS analyses. In addition, the antimelanoma activity of metabolites 2-5 was evaluated against two human melanoma cell lines, Mel-1 (lymph node) and Mel-2 (pleural fluid).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.