In-vitro metabolism of glycyrrhetinic acid by human and rat liver microsomes and its interactions with six CYP substrates

Glycyrrhetinic acid ameliorates diosbulbin B-induced hepatotoxicity in mice by modulating metabolic activation of diosbulbin B

Exposure to diosbulbin B (DBB), the primary component of the herbal medicine Dioscorea bulbifera L. (DB), can cause liver injury in humans and experimental animals. A previous study found DBB-induced hepatotoxicity was initiated by CYP3A4-mediated metabolic activation and subsequent formation of adducts with cellular proteins. The herbal medicine licorice (Glycyrrhiza glabra L.) is frequently combined with DB used in numerous Chinese medicinal formulas in an effort to protect against DB-elicited hepatotoxicity. Importantly, glycyrrhetinic acid (GA), the major bioactive ingredient in licorice, inhibits CYP3A4 activity. The study aimed to investigate the protection of GA against DBB-induced hepatotoxicity and the underlying mechanism. Biochemical and histopathological analysis showed GA alleviated DBB-induced liver injury in a dose-dependent manner. In vitro metabolism assay with mouse liver microsomes (MLMs) indicated that GA decreased the generation of metabolic activation-derived pyrrole-glutathione (GSH) conjugates from DBB. Toxicokinetic studies demonstrated that GA increased maximal serum concentration (Cmax ) and area under the serum-time curve (AUC) of DBB in mice. In addition, GA attenuated hepatic GSH depletion caused by DBB. Further mechanistic studies showed that GA reduced the production of DBB-derived pyrroline-protein adducts in a dose-dependent manner. In conclusion, our findings demonstrated that GA exerted protective effect against DBB-induced hepatotoxicity, mainly correlated with suppressing the metabolic activation of DBB. Therefore, the development of a standardized combination of DBB with GA may protect patients from DBB-induced hepatotoxicity.

Potential herb‒drug interactions between anti-COVID-19 drugs and traditional Chinese medicine

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide. Effective treatments against COVID-19 remain urgently in need although vaccination significantly reduces the incidence, hospitalization, and mortality. At present, antiviral drugs including Nirmatrelvir/Ritonavir (Paxlovid^TM), Remdesivir, and Molnupiravir have been authorized to treat COVID-19 and become more globally available. On the other hand, traditional Chinese medicine (TCM) has been used for the treatment of epidemic diseases for a long history. Currently, various TCM formulae against COVID-19 such as Qingfei Paidu decoction, Xuanfei Baidu granule, Huashi Baidu granule, Jinhua Qinggan granule, Lianhua Qingwen capsule, and Xuebijing injection have been widely used in clinical practice in China, which may cause potential herb-drug interactions (HDIs) in patients under treatment with antiviral drugs and affect the efficacy and safety of medicines. However, information on potential HDIs between the above anti-COVID-19 drugs and TCM formulae is lacking, and thus this work seeks to summarize and highlight potential HDIs between antiviral drugs and TCM formulae against COVID-19, and especially pharmacokinetic HDIs mediated by metabolizing enzymes and/or transporters. These well-characterized HDIs could provide useful information on clinical concomitant medicine use to maximize clinical outcomes and minimize adverse and toxic effects.

Chemical analysis of the Chinese herbal medicine licorice (Gan-Cao): An update review

ETHNOPHARMACOLOGICAL RELEVANCE

Licorice, called Gan-Cao in China, is one of the most popular traditional herbal medicines. It is derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. Licorice is recorded in the pharmacopoeias of China, Japan, US, and Europe.

AIM

This review updates research progress of licorice from the perspectives of chemical analysis, quality evaluation, drug metabolism, and pharmacokinetic studies from 2009 to April 2022.

MATERIALS AND METHODS

Both English and Chinese literatures were collected from databases including PubMed, Elsevier, Web of Science, and CNKI (Chinese). Licorice, extraction, structural characterization/identification, quality control, metabolism, and pharmacokinetics were used as keywords.

RESULTS

Newly developed analytical methods, including LC/UV, 2DLC, LC/MS, GC/MS, and mass spectrometry imaging (MSI) for chemical analysis of licorice were summarized.

CONCLUSION

This review provides a comprehensive summary on chemical analysis of licorice.

Effect of herbal formulation on glimepiride pharmacokinetics and pharmacodynamics in nicotinamide-streptozotocin-induced diabetic rats

BACKGROUND

Traditional medicinal herbs are widely consumed in developing countries to treat diabetes as they are perceived to be safer, less expensive, and have fewer side effects as compared to the conventional medicines. Diabecon (DB), Himalaya Herbal Healthcare, India is herbal over-the-counter formulation which contains several herbs that are reported in the traditional texts for the treatment of diabetes. The majority of these herbs have been investigated and found to interfere with the cytochrome pathway. The most common oral antihyperglycemic drug used today in clinical practice is Glimepiride (GP).The CYP2C9 enzyme is mainly responsible for the metabolism of GP. Herein we hypothesize that the co-administration of GP with DB may result in possible Herb-Drug Interactions (HDIs) as DB has the potential to significantly inhibit the CYP2C9 enzyme.

OBJECTIVE

In the current study, the pharmacokinetic and pharmacodynamic interactions of GP (0.82 mg/kg) with DB (110.95 mg/kg) was investigated in diabetes induced (Nicotinamide-STZ) rats by co-administering both drugs orally for 21 days.

MATERIALS AND METHODS

For the study of the HDI, Bioanalytical RP-HPLC/PDA method for quantifying GP in plasma of rats was developed and validated as per US-FDA guidelines. In vivo pharmacokinetic and pharmacodynamic parameters were studied on day 1 and day 21 post administration.

RESULTS

The RP-HPLC/PDA method was successfully employed for quantification of GP in the PK studies. The co-administration of GP and DB in diabetic rats resulted in beneficial pharmacodynamic interactions, but there were no notable changes in the pharmacokinetic parameters of GP.

CONCLUSION

This current investigation in an animal model suggests that co-administration of GP and DB may have significant therapeutic benefits in the treatment of diabetes; however, additional research, randomized clinical trials or case studies in humans, is needed.

Explore the Potential Ingredients for Detoxification of Honey-Fired Licorice (ZGC) Based on the Metabolic Profile by UPLC-Q-TOF-MS

Licorice is well known for its ability to reduce the toxicity of the whole prescription in traditional Chinese medicine theory. However, honey-fired licorice (ZGC for short), which is made of licorice after being stir-fried with honey water, is more commonly used for clinical practice. The metabolism in vivo and detoxification-related compounds of ZGC have not been fully elucidated. In this work, the chemical constituents in ZGC and its metabolic profile in rats were both identified by high ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The network pharmacology was applied to predict the potential detoxifying ingredients of ZGC. As a result, a total of 115 chemical compounds were identified or tentatively characterized in ZGC aqueous extract, and 232 xenobiotics (70 prototypes and 162 metabolites) were identified in serum, heart, liver, kidneys, feces, and urine. Furthermore, 41 compounds absorbed in serum, heart, liver, and kidneys were employed for exploring the detoxification of ZGC by network pharmacology. Ultimately, 13 compounds (five prototypes including P5, P24, P30, P41 and P44, and 8 phase Ⅰ metabolites including M23, M47, M53, M93, M100, M106, M118, and M134) and nine targets were anticipated to be potential mediums regulating detoxification actions. The network pharmacology analysis had shown that the ZGC could detoxify mainly through regulating the related targets of cytochrome P450 and glutathione. In summary, this study would help reveal potential active ingredients in vivo for detoxification of ZGC and provided practical evidence for explaining the theory of traditional Chinese medicine with modern technology.

Influence of verapamil on the pharmacokinetics of rotundic acid in rats and its potential mechanism

CONTEXT

Rotundic acid (RA), a plant-derived pentacyclic triterpene acid, has been reported to possess extensive pharmacological activities. The poor bioavailability limits its further development and potential clinic application.

OBJECTIVE

To clarify the potential mechanism for poor oral bioavailability.

MATERIALS AND METHODS

The single-dose pharmacokinetics of orally administered RA (10 mg/kg) in Sprague-Dawley rats without or with verapamil (25 or 50 mg/kg) were investigated. Additionally, MDCKII-MDR1 and Caco-2 cell monolayers, five recombinant human cytochrome P450 (rhCYP) enzymes (1A2, 2C8, 2C9, 2D6 and 3A4), and rat liver microsomes were also conducted to investigate its potential mechanism.

RESULTS

Verapamil could significantly affect the plasma concentration of RA. Co-administered verapamil at 25 and 50 mg/kg, the AUC_0-∞ increased from 432 ± 64.2 to 539 ± 53.6 and 836 ± 116 ng × h/mL, respectively, and the oral clearance decreased from 23.6 ± 3.50 to 18.7 ± 1.85 and 12.2 ± 1.85 L/h/kg, respectively. The MDCKII-MDR1 cell assay showed that RA might be a P-gp substrate. The rhCYPs experiments indicated that RA was mainly metabolized by CYP3A4. Additionally, verapamil could increase the absorption of RA by inhibiting the activity of P-gp, and slow down the intrinsic clearance of RA from 48.5 ± 3.18 to 12.0 ± 1.06 µL/min/mg protein.

DISCUSSION AND CONCLUSIONS

These findings indicated that verapamil could significantly affect the pharmacokinetic profiles of RA in rats. It was demonstrated that P-gp and CYP3A were involved in the transport and metabolism of RA, which might contribute to the low oral bioavailability of RA.

Herb-drug interactions in diabetes mellitus: A review based on pre-clinical and clinical data

Global diabetes epidemic is the major cause of fatality and lethality. As per IDF 2019 report, diabetes caused 4.2 million deaths, approximately 463 million people are living with diabetes and by 2045, this will rise to 700 million. Nowadays, the physicians and common people in both developed and developing countries are using medicinal plants and their formulations to treat diseases with the postulation that organic commodities are safe for consumption. These plants may act as inhibitors or inducers of the Cytochrome P450 or transport and efflux proteins or both and may alter gastrointestinal, renal functions leading to Herb-Drug Interactions. This review intends to focus on the frequently employed medicinal plants, their traditional uses, their Cytochrome P450 inhibition or induction activity, phytochemical, and pharmacological effects, established HDI with the help of in vitro tools, in vivo pharmacokinetics and pharmacodynamics studies to understand the impact of herbs on ADME of the drug and whether it is beneficial, harmful or has no effect respectively. This review will help the physicians and other health care professionals as a reference guide to update their knowledge and expertise about HDI. However, more quality research in this area is needed to evaluate the efficacy of many herbal medicines, thereby reducing side effects and improving the safety of patients.

Research progress on the protective effects of licorice-derived 18β-glycyrrhetinic acid against liver injury

The first description of the medical use of licorice appeared in "Shennong Bencao Jing", one of the well-known Chinese herbal medicine classic books dated back to 220-280 AD. As one of the most commonly prescribed Chinese herbal medicine, licorice is known as "Guo Lao", meaning "a national treasure" in China. Modern pharmacological investigations have confirmed that licorice possesses a number of biological activities, such as antioxidation, anti-inflammatory, antiviral, immune regulation, and liver protection. 18β-glycyrrhetinic acid is one of the most extensively studied active integrants of licorice. Here, we provide an overview of the protective effects of 18β-glycyrrhetinic acid against various acute and chronic liver diseases observed in experimental models, and summarize its pharmacological effects and potential toxic/side effects at higher doses. We also make additional comments on the important areas that may warrant further research to support appropriate clinical applications of 18β-glycyrrhetinic acid and avoid potential risks.

Clinical Evaluation of Acetaminophen-Galgeuntang Interaction Based on Population Approaches

Galgeuntang (GGT), a traditional herbal medicine, is widely co-administered with acetaminophen (AAP) for treatment of the common cold, but this combination has not been the subject of investigation. Therefore, we investigated the herb–drug interaction between GGT and AAP by population pharmacokinetics (PKs) modeling and simulation studies. To quantify PK parameters and identify drug interactions, an open label, three-treatment, three-period, one-sequence (AAP alone, GGT alone, and AAP and GGT in combination) clinical trial involving 12 male healthy volunteers was conducted. Ephedrine (EPD), the only GGT component detected, was identified using a one-compartment model. The PKs of AAP were described well by a one-compartment model and exhibited two-phase absorption (rapid followed by slow) and first-order elimination. The model showed that EPD significantly influenced the PKs of AAP. The simulation results showed that at an AAP dose of 1000 mg × 4 times daily, the area under the concentration versus time curve of AAP increased by 16.4% in the presence of GGT compared to AAP only. In conclusion, the PKs of AAP were affected by co-administration of GGT. Therefore, when AAP is combined with GGT, adverse effects related to overdose of AAP could be induced possibly.

Risk assessment of the chiral pesticide fenamiphos in a human model: Cytochrome P450 phenotyping and inhibition studies

Fenamiphos (FS) is a chiral organophosphate pesticide that is used to control nematodes in several crops. Enantioselective differences may be observed in FS activity, bioaccumulation, metabolism, and toxicity. Humans may be exposed to FS through occupational and chronic (food, water, and environmental) exposure. FS may cause undesirable CYP450 pesticide-drug interactions, which may impact human health. Here, the CYP450 isoforms involved in enantioselective FS metabolism were identified, and CYP450 inhibition by rac-FS, (+)-FS, and (-)-FS was evaluated to obtain reliable information on enantioselective FS risk assessment in humans. CYP3A4 and CYP2E1 metabolized FS enantiomers, and CYP2B6 may participate in rac-FS metabolism. In addition, rac-FS, (+)-FS, and (-)-FS were reversible competitive CYP1A2, CYP2C19, and CYP3A4/5 inhibitors. High stereoselective inhibition potential was verified; rac-FS and (-)-FS strongly inhibited and (+)-FS moderately inhibited CYP1A2. Stereoselective differences were also detected for CYP2C19 and CYP3A4/5, which were strongly inhibited by rac-FS, (+)-FS, and (-)-FS. Our results indicated a high potential for CYP450 drug-pesticide interactions, which may affect human health. The lack of stereoselective research on the effect of chiral pesticides on the activity of CYP450 isoforms highlights the importance of assessing the risks of such pesticides in humans.

Simultaneous quantitation of glycyrrhetic acid and puerarin in plasma using ultra flow liquid chromatography tandem mass spectrometry and application in a pharmacokinetics study in healthy and alcoholic liver injury rats

A rapid, sensitive, and accurate ultra flow liquid chromatography tandem mass spectrometry (UFLC-MS/MS ) method was developed and validated for simultaneous quantitation of glycyrrhetic acid and puerarin in plasma derived from healthy and alcoholic liver injury rats. Plasma samples from healthy and model rats were deproteinated with methanol using liquiritin as an internal standard. Chromatography separation was performed by a Waters BEH (ethylene-bridged hybrid) C₁₈ column (2.1 × 50 mm; 1.7 μm) using a gradient elution from acetonitrile and water (containing 0.1% formic acid) and at a flow rate of 0.4 mL/min. Quantitation was performed on a Triple Quad 4500 tandem mass spectrometer coupled with an electrospray ionization source in negative multiple reaction monitoring mode. Specificity, carryover, dilution integrity, recovery, linearity, precision and accuracy, matrix effect, and stability were within acceptable limits. The newly established method was successfully applied to a pharmacokinetics study to investigate glycyrrhetic acid and puerarin in healthy and alcoholic liver injury rats.

Multiple Bioassays and Targeted and Nontargeted Analyses to Characterize Potential Toxicological Effects Associated with Sediments of Masan Bay: Focusing on AhR-Mediated Potency

An enhanced, multiple lines of evidence approach was applied to assess potential toxicological effects associated with polluted sediments. Two in vitro bioassays (H4IIE-luc and Vibrio fischeri) and three in vivo bioassays (microalgae: Isochrysis galbana and Phaeodactylum tricornutum; zebrafish embryo: Danio rerio) were applied. To identify causative chemicals in samples, targeted analyses (polycyclic aromatic hydrocarbons (PAHs), styrene oligomers (SOs), and alkylphenols) and nontargeted full-scan screening analyses (FSA; GC- and LC-QTOFMS) were performed. First, great AhR-mediated potencies were observed in midpolar and polar fractions of sediment extracts, but known and previously characterized AhR agonists, including PAHs and SOs could not fully explain the total potencies of samples. Enoxolone was identified as a novel AhR agonist in a highly potent sediment fraction by use of FSA. Enoxolone has a relative potency of 0.13 compared to benzo[a]pyrene (1.0) in the H4IIE-luc bioassay. Nonylphenols associated with membrane damage that influenced the viability of the microalgae were also observed. Finally, inhibitions of bioluminescence of V. fischeri and lethality of D. rerio embryos were strongly related to nonpolar compounds. Overall, the present work addressed assay- and end point-specific variations and sensitivities for potential toxicities of mixture samples, warranting a significant utility of the "multiple lines of evidence" approach in ecological risk assessment.

Influence of glycyrrhetinic acid on the pharmacokinetics of warfarin in rats

1. Combination of different drugs has been widely applied in clinics in China. Both glycyrrhetinic acid (GA) and warfarin possess various pharmacological activities, the co-administration of them is becoming popular. However, the herb-drug interaction between GA and warfarin is still unknown.2. The herb-drug interaction between GA and warfarin in vivo and in vitro was studied, to clarify the effect of GA on the pharmacokinetics of warfarin and its main mechanism.3. The pharmacokinetics of intragastric administered warfarin (0.5 mg/kg) with or without GA pretreatment (100 mg/kg/day, 7 days) were investigated. The rat liver microsomes incubation systems were used to study the effect of GA on the metabolic stability of warfarin and support the in vivo pharmacokinetic data.4. The pharmacokinetic results indicated that co-administration of GA could increase the systemic exposure of warfarin, including area under the curve (48.87 ± 2.89 µg·h·mL^-1 without GA versus 58.63 ± 1.90 µg·h·mL^-1 with GA), maximum plasma concentration and t_1/2. The metabolic stability of warfarin increased from 23.8 ± 5.9 to 41.4 ± 7.1 min with the pretreatment of GA.5. These results indicated that GA could change the pharmacokinetic profile of warfarin. The metabolism of warfarin was slowed down in rat liver and the systemic exposure increased by GA, via inhibiting the activity of CYP3A4.

Solving the interactions of steroidal ligands with CYP3A4 using a grid-base template system

Using over fifty steroidal ligands, CYP3A4 Template system established in our previous study (DMPK 34: 113-125, 2019) has been evaluated for the applicability for prediction of regioselective metabolisms of steroids in the present study. Plural regional interactions near Site of Oxidation of CYP3A4 (Slide-down and Adaptation) are newly defined for steroid ligands in addition to previously characterized Trigger- and IJL-interactions on Template. Interaction of steroids at ring-A with CYP3A4 residue (Front-residue), at the facial side of Ring B of Template, determined the availability of ligand sitting at Rings A and B of Template. Steroids having 3-one-4-ene structures, which are not stacked on Front-residue, thus slide down for their 6-oxidations. Some steroids with 3β-ol structures undergo the further right-side movement (Adaptation) for their 7-oxidations. Similar overpassing phenomena are also expected for steroid 15/16-oxidations and 2/1-oxidations. Allowable width on ligand accommodation was also defined as Width-gauge of Template. Reciprocal comparison of sittings of steroids on Template with experimental data offered idea of CYP3A4-mediated oxidations of steroids through seven distinct types of placements on Template and of the relationship with their usage abundance. The present system would offer practical way for structural identification and verification of CYP3A4-mediated metabolisms of various types of steroids.

Natural products in licorice for the therapy of liver diseases: Progress and future opportunities

Liver diseases related complications represent a significant source of morbidity and mortality worldwide, creating a substantial economic burden. Oxidative stress, excessive inflammation, and dysregulated energy metabolism significantly contributed to liver diseases. Therefore, discovery of novel therapeutic drugs for the treatment of liver diseases are urgently required. Licorice is one of the most commonly used herbal drugs in Traditional Chinese Medicine for the treatment of liver diseases and drug-induced liver injury (DILI). Various bioactive components have been isolated and identified from the licorice, including glycyrrhizin, glycyrrhetinic acid, liquiritigenin, Isoliquiritigenin, licochalcone A, and glycycoumarin. Emerging evidence suggested that these natural products relieved liver diseases and prevented DILI through multi-targeting therapeutic mechanisms, including anti-steatosis, anti-oxidative stress, anti-inflammation, immunoregulation, anti-fibrosis, anti-cancer, and drug-drug interactions. In the current review, we summarized the recent progress in the research of hepatoprotective and toxic effects of different licorice-derived bioactive ingredients and also highlighted the potency of these compounds as promising therapeutic options for the treatment of liver diseases and DILI. We also outlined the networks of underlying molecular signaling pathways. Further pharmacology and toxicology research will contribute to the development of natural products in licorice and their derivatives as medicines with alluring prospect in the clinical application.

Isolation of a novel glycyrrhizin metabolite as a causal candidate compound for pseudoaldosteronism

Pseudoaldosteronism is a common adverse effect associated with traditional Japanese Kampo medicines. The pathogenesis is mainly caused by 3-monoglucuronyl glycyrrhetinic acid (3MGA), one of the metabolites of glycyrrhizin (GL) contained in licorice. We developed an anti-3MGA monoclonal antibody (MAb) and an ELISA system to easily detect 3MGA in the plasma and urine of the patients. However, we found that some metabolites of GL cross-reacted with this MAb. Mrp2-deficient Eisai Hyperbilirubinemia rats (EHBRs) were administered glycyrrhetinic acid (GA), and we isolated 22α-hydroxy-18β-glycyrrhetyl-3-O-sulfate-30-glucuronide (1) from the pooled urine with the guidance of positive immunostaining of eastern blot as the new metabolite of GL. The IC₅₀ of 1 for type 2 11β-hydroxysteroid dehydrogenase (11β-HSD2) was 2.0 µM. Similar plasma concentrations of 1 and GA were observed 12 h after oral administration of GA to EHBR. Compound 1 was eliminated via urine, whereas GA was not. In Sprague–Dawley (SD) rats orally treated with GA, compound 1 was absent from both the plasma and the urine. Compound 1 was actively transported into cells via OAT1 and OAT3, whereas GA was not. Compound 1, when produced in Mrp2-deficiency, represents a potential causative agent of pseudoaldosteronism, and might be used as a biomarker to prevent the adverse effect.

Application of Metabolomics in the Study of Natural Products

LC-MS-based metabolomics could have a major impact in the study of natural products, especially in its metabolism, toxicity and activity. This review highlights recent applications of metabolomics approach in the study of metabolites and toxicity of natural products, and the understanding of their effects on various diseases. Metabolomics has been employed to study the in vitro and in vivo metabolism of natural compounds, such as osthole, dehydrodiisoeugenol, and myrislignan. The pharmacological effects of natural compounds and extracts were determined using metabolomics technology combined with diseases models in animal, including osthole and nutmeg extracts. It has been demonstrated that metabolomics is a powerful technology for the investigation of xenobiotics-induced toxicity. The metabolism of triptolide and its hepatotoxicity were discussed. LC-MS-based metabolomics has a great potential in the druggability of natural products. The application of metabolomics should be broadened in the field of natural products in the future.

Comparative study of selective in vitro and in silico BACE1 inhibitory potential of glycyrrhizin together with its metabolites, 18α- and 18β-glycyrrhetinic acid, isolated from Hizikia fusiformis

Hizikia fusiformis (Harvey) Okamura is a brown seaweed widely used in Korea and Japan, and it contains different therapeutically active constituents. In the present study, we investigated the activities of glycyrrhizin isolated from H. fusiformis, including its metabolites, 18α- and 18β-glycyrrhetinic acid against Alzheimer's disease (AD) via acetyl and butyrylcholinesterase and β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibition. Among these three compounds, 18β-glycyrrhetinic acid (IC₅₀ = 8.93 ± 0.69 µM) demonstrated two fold potent activity against BACE1 compared to the positive control, quercetin (IC₅₀ = 20.18 ± 0.79 µM). Additionally, glycyrrhizin with an IC₅₀ value of 20.12 ± 1.87 µM showed similarity to quercetin, while 18α-glycyrrhetinic acid showed moderate activity (IC₅₀ = 104.35 ± 2.84 µM). A kinetic study revealed that glycyrrhizin and 18β-glycyrrhetinic acid were non-competitive and competitive inhibitiors of BACE1, demonstrated via K _i values of 16.92 and 10.91 µM, respectively. Molecular docking simulation studies evidently revealed strong binding energy of these compounds for BACE1, indicating their high affinity and capacity for tighter binding to the active site of the enzyme. These data suggest that glycyrrhizin isolated from the edible seaweed, H. fusiformis and its metabolite, 18β-glycyrrhetinic acid demonstrated selective inhibitory activity against BACE1 to alleviate AD.

Enhanced oral bioavailability of glycyrrhetinic acid via nanocrystal formulation

The purpose of this study was to prepare solid nanocrystals of glycyrrhetinic acid (GA) for improved oral bioavailability. The anti-solvent precipitation-ultrasonication method followed by freeze-drying was adopted for the preparation of GA nanocrystals. The physicochemical properties, drug dissolution and pharmacokinetic of the obtained nanocrystals were investigated. GA nanocrystals showed a mean particle size of 220 nm and shaped like short rods. The analysis results from differential scanning calorimetry and X-ray powder diffraction indicated that GA remained in crystalline state despite a huge size reduction. The equilibrium solubility and dissolution rate of GA nanocrystal were significantly improved in comparison with those of the coarse GA or the physical mixture. The bioavailability of GA nanocrystals in rats was 4.3-fold higher than that of the coarse GA after oral administration. With its rapid dissolution and absorption performance, the solid nanocrystal might be a more preferable formulation for oral administration of poorly soluble GA.

Modulation of Hepatic Cytochrome P450 Enzymes by Curcumin and its Pharmacokinetic Consequences in Sprague-dawley Rats

Background:

Curcumin (CUR) is a polyphenolic component derived from an herbal remedy and dietary spice turmeric (Curcuma longa).

Objective:

The aim of this study was to investigate inhibitory effects of CUR on in vitro cytochrome P450 (CYP) activity and in vivo pharmacokinetic consequences of single CUR dose in rats.

Materials and Methods:

An in vitro CYP inhibition study in rat liver microsomes (RLM) was conducted using probe substrates for CYPs. Then, an in vivo pharmacokinetics of intravenous buspirone (BUS), a probe substrate for CYP3A, was studied with the concurrent administration of oral CUR in rats.

Results:

In the in vitro CYP inhibition study, CUR inhibited the CYP3A-mediated metabolism of testosterone (TES) with a half maximal inhibitory concentration of 11.0 ± 3.3 μM. However, the impact of a single oral CUR dose on the pharmacokinetics of BUS in rats is limited, showing that CUR cannot function as an inhibitor for CYP3A-mediated drug metabolism in vivo.

Conclusion:

To the best of our knowledge, our results are the first reported data regarding the inhibition of in vitro CYP3A-mediated metabolism of TES and the in vivo impact of a single CUR dose on the pharmacokinetics of BUS in rats. Further study is required to draw a confirmative conclusion on whether CUR can be a clinically relevant CYP3A4 inhibitor.

SUMMARY

CUR can inhibit the in vitro CYP3A-mediated metabolism of TES in RLM. However, the impact of a single oral CUR dose on the pharmacokinetics of BUS in rats is limited, showing that CUR cannot function as an inhibitor for CYP3A-mediated drug metabolism in vivo.

Glycyrrhiza glabra

Liquorice foliage

In Vitro and in Vivo Inhibitory Effects of Glycyrrhetinic Acid in Mice and Human Cytochrome P450 3A4

Glycyrrhetinic acid (GA) has been used clinically in the treatment of patients with chronic hepatitis. This study evaluated the effect of GA on the activity of five P450(CYP450) cytochrome enzymes: CYP2A6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, in human liver microsomes (HLMs) and recombinant cDNA-expressed enzyme systems using a HPLC-MS/MS CYP-specific probe substrate assay. With midazolam as the probe substrate, GA greatly decreased CYP3A4 activity with IC50 values of 8.195 μM in HLMs and 7.498 μM in the recombinant cDNA-expressed CYP3A4 enzyme system, respectively. It significantly decreased CYP3A4 activity in a dose- but not time-dependent manner. Results from Lineweaver-Burk plots showed that GA could inhibit CYP3A4 activity competitively, with a Ki value of 1.57 μM in HLMs. Moreover, CYP2C9 and CYP2C19 could also be inhibited significantly by GA with IC50 of 42.89 and 40.26 μM in HLMs, respectively. Other CYP450 isoforms were not markedly affected by GA. The inhibition was also confirmed by an in vivo study of mice. In addition, it was observed that mRNA expressions of the Cyps2c and 3a family decreased significantly in the livers of mice treated with GA. In conclusion, this study indicates that GA may exert herb-drug interactions by competitively inhibiting CYP3A4.

Metabolic interactions of magnolol with cytochrome P450 enzymes: uncompetitive inhibition of CYP1A and competitive inhibition of CYP2C

Magnolol (MAG; 5,5'-diallyl-2,2'-biphenyldiol) is a major bioactive component of Magnolia officinalis. We investigated the metabolic interactions of MAG with hepatic cytochrome P450 monooxygenase (CYP) through in vitro microsomal metabolism study using human (HLM) and rat liver microsomes (RLM). CYP2C and 3A subfamilies were significantly involved in the metabolism of MAG, while CYP1A subfamily was not in HLM and RLM. The relative contribution of phase I enzymes including CYP to the metabolism of MAG was comparable to that of uridine diphosphate glucuronosyltransferase (UGT) in RLM. Moreover, MAG potently inhibited the metabolic activity of CYP1A (IC50 of 1.62 μM) and 2C (IC50 of 5.56 μM), while weakly CYP3A (IC50 of 35.0 μM) in HLM and RLM. By the construction of Dixon plot, the inhibition type of MAG on CYP activity in RLM was determined as follows: uncompetitive inhibitor for CYP1A (Ki of 1.09-12.0 μM); competitive inhibitor for CYP2C (Ki of 10.0-15.2 μM) and 3A (Ki of 93.7-183 μM). Based on the comparison of the current IC50 and Ki values with a previously reported liver concentration (about 13 μM) of MAG after its seven times oral administration at a dose of 50 mg/kg in rats, it is suggested that MAG could show significant inhibition of CYP1A and 2C, but not CYP3A, in the in vivo rat system. These results could lead to further studies in clinically significant metabolism-mediated MAG-drug interactions.

Modulation of Cytochrome P450 Activity by 18β-Glycyrrhetic Acid and its Consequence on Buspirone Pharmacokinetics in Rats

The aim of this study was to elucidate the inhibition mechanism of 18β-glycyrrhetic acid (GLY) on cytochrome P450 (CYP) activity and in vivo pharmacokinetic consequences of single GLY dose in rats. An in vitro CYP inhibition study in rat liver microsomes (RLM) was conducted using probe substrates for CYPs. Then, an in vivo pharmacokinetics of intravenous and oral buspirone (BUS), a probe substrate for CYP3A, was studied with the concurrent administration of oral GLY in rats. In the in vitro CYP inhibition study, CYP3A was involved in the metabolism of GLY. Moreover, GLY inhibited CYP3A activity with an IC50 of 20.1 ± 10.7 μM via a mixed inhibition mechanism. In the in vivo rat pharmacokinetic study, single oral GLY dose enhanced the area under plasma concentration-time curve (AUC) of intravenous and oral BUS, but the extent of increase in AUC was only minimal (1.12-1.45 fold). These results indicate that GLY can inhibit the in vitro CYP3A-mediated drug metabolism in RLM via a mixed inhibition mechanism. However, the impact of single oral GLY dose on the pharmacokinetics of BUS in rats was limited, showing that GLY could function as merely a weak inhibitor for CYP3A-mediated drug metabolism in vivo. Copyright © 2015 John Wiley & Sons, Ltd.

Peony-Glycyrrhiza Decoction, an Herbal Preparation, Inhibits Clozapine Metabolism via Cytochrome P450s, but Not Flavin-Containing Monooxygenase in In Vitro Models

Our previous studies have shown the therapeutic efficacy and underlying mechanisms of Peony-Glycyrrhiza Decoction (PGD), an herbal preparation, in treating antipsychotic-induced hyperprolactinemia in cultured cells, animal models, and human subjects. In the present study, we further evaluated pharmacokinetic interactions of PGD with clozapine (CLZ) in human liver microsomes (HLM), recombinantly expressed cytochrome P450s (P450s), and flavin-containing monooxygenases (FMOs). CLZ metabolites, N-demethyl-clozapine and clozapine-N-oxide, were measured. PGD, individual peony and glycyrrhiza preparations, and the two individual preparations in combination reduced production of CLZ metabolites to different extents in HLM. While the known bioactive constituents of PGD play a relatively minor role in the kinetic effects of PGD on P450 activity, PGD as a whole had a weak-to-moderate inhibitory potency toward P450s, in particular CYP1A2 and CYP3A4. FMOs are less actively involved in mediating CLZ metabolism and the PGD inhibition of CLZ. These results suggest that PGD has the capacity to suppress CLZ metabolism in the human liver microsomal system. This suppression is principally associated with the inhibition of related P450 activity but not FMOs. The present study provides in vitro evidence of herb-antipsychotic interactions.

Potential drug interactions associated with glycyrrhizin and glycyrrhetinic acid

Glycyrrhizin (GZ), the main active component of licorice, is a widely used therapeutic in the clinic. Depending on the disease, the treatment may involve a long course of high dose GZ. Another component of licorice, glycyrrhetinic acid (GA), is the main active metabolite of GZ and is thought to be responsible for the majority of the pharmacological properties of GZ. Therefore, GZ and GA are both used for therapeutic purposes. In addition, GZ and GA are also widely used to sweeten and flavor foods. Due to this widespread, multifaceted use of these substances, potential drug interactions with GZ and GA have recently gained attention. Along these lines, this review covers the known effects of GZ and GA on drug-metabolizing enzymes and efflux transporters. We conclude that both GZ and GA may have an effect on the activity of CYPs. For example, GZ may induce CYP3A activity through activation of PXR. Also, GZ and GA may affect glucuronidation in rats and humans. Furthermore, 18β-GA is a potent inhibitor of P-gp, while GZ and GA are inhibitors of MRP1, MRP2 and BCRP. The pharmacokinetics and pharmacodynamics of many medications may be altered when used concurrently with GZ or GA, which is also covered in this review. Overall, GZ, GA or related products should be taken with caution when taken with additional medications due to the possible drug interactions.

In vitro metabolism of the lignan (-)-grandisin, an anticancer drug candidate, by human liver microsomes

(-)-grandisin is a tetrahydrofuran lignan that displays important biological properties, such as trypanocidal, anti-inflammatory, cytotoxic, and antitumor activities, suggesting its utility as a potential drug candidate. One important step in drug development is metabolic characterization and metabolite identification. To perform a biotransformation study of (-)-grandisin and to determine its kinetic properties in humans, a high performance liquid chromatography (HPLC) method was developed and validated. After HPLC method validation, the kinetic properties of (-)-grandisin were determined. (-)-grandisin metabolism obeyed Michaelis-Menten kinetics. The maximal reaction rate (Vmax ) was 3.96 ± 0.18 µmol/mg protein/h, and the Michaelis-Menten constant (Km ) was 8.23 ± 0.99 μM. In addition, the structures of the metabolites derived from (-)-grandisin were characterized via gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) analysis. Four metabolites, 4-O-demethylgrandisin, 3-O-demethylgrandisin, 4,4'-di-O-demethylgrandisin, and a metabolite that may correspond to either 3,4-di-O-demethylgrandisin or 3,5-di-O-demethylgrandisin, were detected. CYP2C9 isoform was the main responsible for the formation of the metabolites. These metabolites have not been previously described, demonstrating the necessity of assessing (-)-grandisin metabolism using human-derived materials.

Bioactive components of Glycyrrhiza uralensis mediate drug functions and properties through regulation of CYP450 enzymes

Glycyrrhiza uralensis (G. uralensis) is a common medicinal plant that has mainly been used to modulate the pharmaceutical activity of herbal medicines. Although G. uralensis has been shown to affect the expression and activity of the key metabolic enzyme cytochrome P450 (CYP450), the detailed mechanism of this process has yet to be elucidated. The present study aimed to elucidate the effects of bioactive components of G. uralensis on different isoforms of CYP450 and determine the ability of these components to modulate drug properties. In the present study, mRNA levels of CYP1A2, CYP2D6, CYP2E1, and CYP3A4 were investigated by quantitative polymerase chain reaction (qPCR) in HepG2 cells following treatment with the major bioactive compounds of G. uralensis. The activity of CYP450 enzymes was investigated in human liver microsomes using the cocktail probe drug method, and the metabolites of specific probes were detected by UPLC‑MS/MS. The effects of G. uralensis on CYP450 were assessed using bioinformatics network analysis. Several compounds from G. uralensis had various effects on the expression and activity of multiple CYP450 isoforms. The majority of the compounds analysed the inhibited expression of CYP2D6 and CYP3A4. Several CYP isoforms were differentially modulated depending on the specific compound and dose tested. In conclusion, the present study suggested that G. uralensis influenced the expression and activity of CYP450 enzymes. Therefore, caution should be taken when G. uralensis is co‑administered with drugs that are known to be metabolized by CYP450. This study contributed to the knowledge of the mechanisms by which this medicinal plant, commonly known as licorice, modulates drug efficacy.

Identification of key licorice constituents which interact with cytochrome P450: evaluation by LC/MS/MS cocktail assay and metabolic profiling

Licorice has been shown to affect the activities of several cytochrome P450 enzymes. This study aims to identify the key constituents in licorice which may affect these activities. Bioactivity assay was combined with metabolic profiling to identify these compounds in several complex licorice extracts. Firstly, the inhibition potencies of 40 pure licorice compounds were tested using an liquid chromatography/tandem mass spectrometry cocktail method. Significant inhibitors of human P450 isozymes 1A2, 2C9, 2C19, 2D6, and 3A4 were then selected for examination of their structural features by molecular docking to determine their molecular interaction with several P450 isozymes. Based on the present in vitro inhibition findings, along with our previous in vivo metabolic studies and the prevalence of individual compounds in licorice extract, we identified several licorice constituents, viz., liquiritigenin, isoliquiritigenin, together with seven isoprenylated flavonoids and arylcoumarins, which could be key components responsible for the herb-drug interaction between cytochrome P450 and licorice. In addition, hydrophilic flavonoid glycosides and saponins may be converted into these P450 inhibitors in vivo. These studies represent a comprehensive examination of the potential effects of licorice components on the metabolic activities of P450 enzymes.