Inhibition of CYP2C9 by natural products: insight into the potential risk of herb-drug interactions

Physcion inhibition of CYP2C9, 2D6 and 3A4 in human liver microsomes

CONTEXT

The effect of the active ingredients in traditional Chinese medicines on the activity of cytochrome P450 enzymes (CYP450s) is a critical factor that should be considered in TCM prescriptions. Physcion, the major active ingredient of Rheum spp. (Polygonaceae), possesses wide pharmacological activities.

OBJECTIVES

The effect of physcion on CYP450 activity was investigated to provide a theoretical basis for use.

MATERIALS AND METHODS

The experiments were conducted in pooled human liver microsomes (HLMs). The activity of CYP450 isoforms was evaluated with corresponding substrates and probe reactions. Blank HLMs were set as negative controls, and typical inhibitors were employed as positive controls. The inhibition model was fitted with Lineweaver Burk plots. The concentration (0, 2.5, 5, 10, 25, 50 and 100 μM physcion) and time-dependent (0, 5, 10, 15 and 30 min) effects of physcion were also assessed.

RESULTS

Physcion suppressed CYP2C9, 2D6 and 3A4 in a concentration-dependent manner with IC50 values of 7.44, 17.84 and 13.50 μM, respectively. The inhibition of CYP2C9 and 2D6 was competitive with the Ki values of 3.69 and 8.66 μM, respectively. The inhibition of CYP3A4 was non-competitive with a Ki value of 6.70 μM. Additionally, only the inhibition of CYP3A4 was time-dependent with the KI and Kinact parameters of 3.10 μM-1 and 0.049 min-1, respectively.

CONCLUSIONS

The inhibition of CYP450s by physcion should be considered in its clinical prescription, and the study design can be employed to evaluate the interaction of CYP450s with other herbs.

A comprehensive review on pharmacokinetic mechanism of herb-herb/drug interactions in Chinese herbal formula

Oral administration of Chinese Herbal Medicine (CHM) faces various challenges in reaching the target organs including absorption and conversion in the gastrointestinal tract, hepatic metabolism via the portal vein, and eventual systemic circulation. During this process, factors such as gut microbes, physical or chemical barriers, metabolic enzymes, and transporters play crucial roles. Particularly, interactions between different herbs in CHM have been observed both in vitro and in vivo. In vitro, interactions typically manifest as detectable physical or chemical changes, such as facilitating solubilization or producing precipitates when decoctions of multiple herbs are administered. In vivo, such interactions cause alterations in the ADME (absorption, distribution, metabolism, and excretion) profile on metabolic enzymes or transporters in the body, leading to competition, antagonism, inhibition, or activation. These interactions ultimately contribute to differences in the therapeutic and pharmacological effects of multi-herb formulas in CHM. Over the past two thousand years, China has cultivated profound expertise and solid theoretical frameworks over the scientific use of herbs. The combination of multiple herbs in one decoction has been frequently employed to synergistically enhance therapeutic efficacy or mitigate toxic and side effects in clinical settings. Additionally combining herbs with increased toxicity or decreased effect is also regarded as a remedy, a practice that should be approached with caution according to Traditional Chinese Medicine (TCM) physicians. Such historical records and practices serve as a foundation for predicting favorable multi-herb combinations and their potential risks. However, systematic data that are available to support the clinical practice and the exploration of novel herbal formulas remain limited. Therefore, this review aims to summarize the pharmacokinetic interactions and mechanisms of herb-herb or herb-drug combinations from existing works, and to offer guidance as well as evidence for optimizing CHM and developing new medicines with CHM characteristics.

Unravelling the complexities of non-alcoholic steatohepatitis: The role of metabolism, transporters, and herb-drug interactions

Nonalcoholic fatty liver disease (NAFLD) is a mainstream halting liver disease with high prevalence in North America, Europe, and other world regions. It is an advanced form of NAFLD caused by the amassing of fat in the liver and can progress to the more severe form known as non-alcoholic steatohepatitis (NASH). Until recently, there was no authorized pharmacotherapy reported for NASH, and to improve the patient's metabolic syndrome, the focus is mainly on lifestyle modification, weight loss, ensuring a healthy diet, and increased physical activity; however, the recent approval of Rezdiffra (Resmetirom) by the US FDA may change this narrative. As per the reported studies, there is an increased articulation of uptake and efflux transporters of the liver, including OATP and MRP, in NASH, leading to changes in the drug's pharmacokinetic properties. This increase leads to alterations in the pharmacokinetic properties of drugs. Furthermore, modifications in Cytochrome P450 (CYP) enzymes can have a significant impact on these properties. Xenobiotics are metabolized primarily in the liver and constitute liver enzymes and transporters. This review aims to delve into the role of metabolism, transport, and potential herb-drug interactions in the context of NASH.

Selective inhibitory effects of suberosin on CYP1A2 in human liver microsomes

Suberosin is a natural phytoconstituent isolated from Citropsis articulata, especially employed for its anticoagulant properties. Although metabolic studies assessing suberosin have been conducted, it is possible interactions with drugs and food have not yet been investigated. In the present study, we analyzed the selective inhibitory effects of suberosin on cytochrome P450 (CYP) enzymes using a cocktail probe assay. Various concentrations of suberosin (0-50 μM) were incubated with isoform-specific CYP probes in human liver microsomes (HLMs). We found that suberosin significantly inhibited CYP1A2-catalyzed phenacetin O-deethylation, exhibiting IC50 values of 9.39 ± 2.05 and 3.07 ± 0.45 μM with and without preincubation in the presence of β-NADPH, respectively. Moreover, suberosin showed concentration-dependent, but not time-dependent, CYP1A2 inhibition in HLMs, indicating that suberosin acts as a substrate and reversible CYP1A2 inhibitor. Using a Lineweaver-Burk plot, we found that suberosin competitively inhibited CYP1A2-catalyzed phenacetin O-deethylation. Furthermore, suberosin showed similar inhibitory effects on recombinant human CYP1A1 and 1A2. In conclusion, suberosin may elicit herb-drug interactions by selectively inhibiting CYP1A2 during the concurrent administration of drugs that act as CYP1A2 substrates.

Evaluation of the impact of vindoline, an active components of Catharanthus roseus, on rat hepatic cytochrome P450 enzymes by using a cocktail of probe drugs

The objection of this study was to investigate the effects of vindoline(VDL) on the cytochrome P450 (CYP 450) isoforms (CYP1A2, 2B, 2C11, 2D1 and 3A) in rats. Firstly, the rats were randomly divided into VDL pretreatment group and blank group, each group had six rats. VDL pretreatment group was administrated VDL (20 mg·kg-1) by oral gavage for fifteen days consecutively, and the equivalent CMC-Na solution without VDL was given to the blank group by gavage. Secondly, a cocktail of caffeine, bupropion, diclofenac, dextromethorphan and midazolam was then administered on the sixteenth day. Finally, blood samples were collected at the specified time point, and the plasma concentration of the probe drug was determined by UHPLC-QTOF-MS/MS. The effects of VDL on the activity of these CYP enzymes in rats were evaluated by pharmacokinetic parameters. VDL pretreatment group compared with the blank group, accelerated the metabolism of diclofenac, and weakened the metabolism of caffeine. These results suggested that VDL could induce the activity of CYP2C11, and inhibits the activity of CYP1A2, but had no significant effects on CYP2B, CYP2D1 and CYP3A. The results in this study can provide beneficial information for the later clinical application of VDL.

Inhibitory effect of quercetin-3-O-α-rhamnoside, p-coumaric acid, phloridzin and 4-O-β-glucopyranosyl-cis-coumaric acid on rats liver microsomes cytochrome P450 enzyme activities

P-coumaric acid, phloridzin, quercetin-3-O-α-rhamnoside and 4-O-β-glucopyranosyl-cis-coumaric acid isolated in Malus micromalus Makino fruit were investigated the inhibitory activity of cytochrome CYP450 enzyme by the probe test method of rat liver microsomes in vitro, and determined the role in drug metabolism and/or toxicology. Enzymatic kinetics method was used to determine the inhibition type of these components and corresponding inhibition constants. The results demonstrated that all the 4 compounds had no significance to inhibit the activities of CYP2E1 and CYP2C11. P-coumaric acid, phloridzin and quercetin-3-O-α-rhamnoside had a weak inhibitory effect on CYP3A4, which belonged to the competitive inhibitory type with inhibitory constants of 10.56, 30.79 and 40.29 μmol L-1, respectively. 4-O-β-glucopyranosyl-cis-coumaric acid had a moderate inhibitory effect on CYP3A4, which belonged to the anti-competitive inhibition type and the inhibition constant was 5.56 μmol L-1. The CYP1A2 could be weakly inhibited by p-coumaric acid in the competitive type, and the inhibition constant is 25.20 μmol L-1 4-O-β-glucopyranosyl-cis-coumaric acid exhibited anti-competitive inhibition of CYP1A2 with an inhibition constant of 19.91 μmol L-1, and the inhibition effect was weak. The results will be useful to optimize the clinical dosage regimen and avoid drug-drug interactions when it is utilized comminating with other medicines in the clinic.

Small molecules to perform big roles: The search for Parkinson's and Huntington's disease therapeutics

Neurological motor disorders (NMDs) such as Parkinson's disease and Huntington's disease are characterized by the accumulation and aggregation of misfolded proteins that trigger cell death of specific neuronal populations in the central nervous system. Differential neuronal loss initiates the impaired motor control and cognitive function in the affected patients. Although major advances have been carried out to understand the molecular basis of these diseases, to date there are no treatments that can prevent, cure, or significantly delay the progression of the disease. In this context, strategies such as gene editing, cellular therapy, among others, have gained attention as they effectively reduce the load of toxic protein aggregates in different models of neurodegeneration. Nevertheless, these strategies are expensive and difficult to deliver into the patients' nervous system. Thus, small molecules and natural products that reduce protein aggregation levels are highly sought after. Numerous drug discovery efforts have analyzed large libraries of synthetic compounds for the treatment of different NMDs, with a few candidates reaching clinical trials. Moreover, the recognition of new druggable targets for NMDs has allowed the discovery of new small molecules that have demonstrated their efficacy in pre-clinical studies. It is also important to recognize the contribution of natural products to the discovery of new candidates that can prevent or cure NMDs. Additionally, the repurposing of drugs for the treatment of NMDs has gained huge attention as they have already been through clinical trials confirming their safety in humans, which can accelerate the development of new treatment. In this review, we will focus on the new advances in the discovery of small molecules for the treatment of Parkinson's and Huntington's disease. We will begin by discussing the available pharmacological treatments to modulate the progression of neurodegeneration and to alleviate the motor symptoms in these diseases. Then, we will analyze those small molecules that have reached or are currently under clinical trials, including natural products and repurposed drugs.

Alpinetin suppresses CYP3A4, 2C9, and 2E1 activity in vitro

CONTEXT

Alpinetin, the major active constitutes of Alpinia katsumata Hayata (Zingiberaceae), has been demonstrated to possess the activity of anti-breast cancer. Cytochrome P450 enzymes (CYP450s) plays vital roles in the biotransformation of various drugs.

OBJECTIVE

To assess the effect of alpinetin on the activity of CYP450s and estimate the inhibition characteristics.

MATERIALS AND METHODS

The activity of CYP450s was evaluated in pooled human liver microsomes with corresponding substrates and marker reactions. The effect of alpinetin was compared with blank control (negative control) and corresponding inhibitors (positive control). The dose-dependent and time-dependent experiments were conducted in the presence of 0, 2.5, 5, 10, 25, 50, and 100 μM alpinetin and incubated for 0, 5, 10, 15, and 30 min.

RESULTS

Alpinetin suppressed CYP3A4, 2C9, and 2E1 activity. All the inhibitions were significantly influenced by alpinetin contration with the IC₅₀ values of 8.23 μM (CYP3A4), 12.64 μM (CYP2C9), and 10.97 μM (CYP2E1), respectively. The inhibition of CYP3A4 was fitted with the non-competitive model with a Ki value of 4.09 μM and was time-dependent with KI and Kinact values of 4.67 min and 0.041 μM^-1, respectively. While CYP2C9 and 2E1 were inhibited by alpinetin competitively with Ki values of 6.42 (CYP2C9) and 5.40 μM (CYP2E1), respectively, in a time-independent manner.

DISCUSSION AND CONCLUSION

The in vitro inhibitory effect of alpineticn on CYP3A, 2C9, and 2E1 implied the potential interaction of alpinetin or its origin herbs with the drugs metabolised by those CYP450s, which needs further in vivo validation.

Joint Analysis of Phenotypic and Genomic Diversity Sheds Light on the Evolution of Xenobiotic Metabolism in Humans

Variation in genes involved in the absorption, distribution, metabolism, and excretion of drugs (ADME) can influence individual response to a therapeutic treatment. The study of ADME genetic diversity in human populations has led to evolutionary hypotheses of adaptation to distinct chemical environments. Population differentiation in measured drug metabolism phenotypes is, however, scarcely documented, often indirectly estimated via genotype-predicted phenotypes. We administered seven probe compounds devised to target six cytochrome P450 enzymes and the P-glycoprotein (P-gp) activity to assess phenotypic variation in four populations along a latitudinal transect spanning over Africa, the Middle East, and Europe (349 healthy Ethiopian, Omani, Greek, and Czech volunteers). We demonstrate significant population differentiation for all phenotypes except the one measuring CYP2D6 activity. Genome-wide association studies (GWAS) evidenced that the variability of phenotypes measuring CYP2B6, CYP2C9, CYP2C19, and CYP2D6 activity was associated with genetic variants linked to the corresponding encoding genes, and additional genes for the latter three. Instead, GWAS did not indicate any association between genetic diversity and the phenotypes measuring CYP1A2, CYP3A4, and P-gp activity. Genome scans of selection highlighted multiple candidate regions, a few of which included ADME genes, but none overlapped with the GWAS candidates. Our results suggest that different mechanisms have been shaping the evolution of these phenotypes, including phenotypic plasticity, and possibly some form of balancing selection. We discuss how these contrasting results highlight the diverse evolutionary trajectories of ADME genes and proteins, consistent with the wide spectrum of both endogenous and exogenous molecules that are their substrates.

Inhibition of imrecoxib on mRNA and protein expression of CYP2C11 enzyme in rats

PURPOSE

To evaluate the effect of imrecoxib on CYP2C11 enzyme activity, mRNA and protein expression.

METHOD

An ultra-performance liquid chromatography (UPLC) method was established. Tolbutamide was selected as CYP2C11 enzyme-specific probe drug and incubated with imrecoxib in rat liver microsomes. The amount of 4-hydroxytolbutamide produced was measured by UPLC to investigate the effect of imrecoxib on CYP2C11 enzyme activity. Imrecoxib (10 mg/kg) was given by intragastric administration twice daily. After 1, 7 and 14 days of administration, liver tissues were taken. The expression of CYP2C11 enzyme mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR), and its protein expression was determined by Western Blot.

RESULTS

Imrecoxib concentration was inversely proportional to the production of 4-hydroxytolbutamide in liver microsomes. Imrecoxib demonstrated dose-dependent inhibitory effect on CYP2C11 activity with IC50=74.77 μM. After administration, RT-PCR showed CYP2C11 enzyme mRNA expressions were 65% (P<0.05), 35%, and 34% of control group, respectively (P<0.01). Western Blot showed CYP2C11 enzyme protein expressions were 80%, 37%, and 34% of control group, respectively (P<0.01).

CONCLUSION

Imrecoxib can reduce mRNA and protein expression of CYP2C11 enzyme in rat liver and inhibit the activity of CYP2C11 enzyme in a dose-dependent manner. However, it will not produce clinically significant drug interactions.

Aidi injection altered the activity of CYP2D4, CYP1A2, CYP2C19, CYP3A2, CYP2E1 and CYP2C11 in normal and diethylnitrosamine-induced hepatocellular carcinoma in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aidi injection (ADI), a traditional chinese medicine preparation, is widely used in combination with chemotherapy for the treatment of various malignant tumors, such as hepatocellular carcinoma (HCC). Studies have shown that changes in cytochrome P450 (CYP450) activity in disease states would affect the metabolism of drugs in vivo, especially liver diseases. However, the changes of Aidi injection on the activities of CYP2D4, CYP1A2, CYP2C19, CYP3A2, CYP2E1 and CYP2C11 in normal and HCC states are still unknown.

AIM OF THE STUDY

The cocktail probe drugs method was used to investigate the effects of ADI on the activity of CYP2D4, CYP1A2, CYP2C19, CYP3A2, CYP2E1 and CYP2C11 in normal and HCC rats.

MATERIALS AND METHODS

The HCC rats was induced by diethylnitrosamine (DEN). Then, both normal and HCC rats were randomly divided into 2 groups (n = 6). They were given saline or ADI (10 mL/kg/d, i.p) for 2 weeks, respectively. On the fifteenth day, cocktail probe mixing solution, including metoprolol (10 mg/kg), caffeine (1.0 mg/kg), omeprazole (2.0 mg/kg), midazolam (2.0 mg/kg), chlorzoxazone (4.0 mg/kg) and tolbutamide (0.5 mg/kg), was injected into tail vein of all rats in each group. The blood sample was obtained at specified time. After the protein is precipitated, six probe drugs are analyzed by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).

RESULTS

Compared with control group, the activity of CYP3A2 and CYP2E1 was significantly lower in the ADI group. Compared with the model group, the activities of CYP1A2, CYP3A2, CYP2E1, and CYP2C11 enzymes in the ADI model group were significantly reduced. Additionally, the activity of CYP2D4, CYP1A2, CYP2C19, CYP3A2, CYP2E1 and CYP2C11 enzymes in model group was significantly lower than control group.

CONCLUSIONS

ADI can inhibit a lot of CYP450 enzyme, so it may reduce the dosage of chemotherapeutic drugs to reach the required plasma concentration of chemotherapeutic drugs, which is of great significance for the combination of anti-tumor chemotherapeutic drugs and is worthy of further in-depth study and clinical attention.

Quantitation of Diclofenac, Tolbutamide, and Warfarin as Typical CYP2C9 Substrates in Rat Plasma by UPLC-MS/MS and Its Application to Evaluate Linderane-Mediated Herb-Drug Interactions

Linderane (LDR), the main active and distinctive component of L. aggregate, is a mechanism-based inactivator of CYP2C9 in vitro, indicating the occurrence of herb-drug interactions. However, little is known about the changes of the pharmacokinetic properties of the common clinical drugs as CYP2C9 substrates after coadministration with LDR. In this study, a selective and rapid ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method for the determination of diclofenac, tolbutamide, and warfarin as CYP2C9 substrates in rat plasma has been developed. Chlorzoxazone was employed as an internal standard (IS), and protein precipitation was used for sample preparation. Chromatographic separation was achieved on a UPLC BEH-C₁₈ (2.1 × 50 mm, 1.7 µm) with 0.1% (v:v) formic acid in water (A) and acetonitrile (B) as the mobile phase with gradient elution. The total run time was only 3.8 min. MS analysis was performed under multiple reaction monitoring (MRM) with electron spray ionization (ESI) operated in the negative mode. The bioanalytical method was validated, and the selectivity, carryover effects, linearity, precision, accuracy, matrix effect, extraction recovery, and stability were acceptable. The validated method was then successfully applied for evaluating the potential pharmacokinetic interactions when LDR was used along with diclofenac, tolbutamide, and warfarin, respectively. Results showed that the C _max of diclofenac in the treated group was 1287.82 ± 454.16 μg/L, which was about 5-fold of that in the control group (P < 0.01). The C _max of tolbutamide in the treated group was 60.70 ± 10.70 mg/L, which was significantly decreased by about 25% when compared with the control group (P < 0.01). The V _d of warfarin in the treated group was obviously increased, which was about 1.4-fold of that in the control group (P < 0.01).

Influence of Gegenqinlian Decoction on Pharmacokinetics and Pharmacodynamics of Atorvastatin Calcium in Hyperlipidemic Rats

BACKGROUND AND OBJECTIVES

Gegenqinlian decoction (GQD), a classic traditional Chinese medicine (TCM), was described in Shanghan Lun. GQD is often combined with antihyperlipidemic drugs (mainly atrovastatin calcium) in TCM clinics. However, the herb-drug interaction between GQD and atrovastatin calcium (AC) is still unknown. To determine whether the combination is safe, we evaluated the effects of GQD on the activities of cytochrome P450 (CYP) 3A2 enzyme and investigated the impact of GQD on the pharmacokinetics and pharmacodynamics of AC in rats.

METHODS

The pharmacokinetics of AC (10 mg/kg) with or without pretreatment with GQD (freeze-dried powder, 1.35 g/kg) were investigated using HPLC. The influence of GQD on pharmacodynamics of AC were determined by detecting the levels of serum total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Moreover, the probe drug method was used to explore the effect of GQD on CYP3A2 activity.

RESULTS

The pharmacokinetic parameters of AC combined with GQD were significantly affected (P < 0.05) in hyperlipidemic rats. The serum TC, TG and LDL-C levels of the combination were significantly reduced (P < 0.05), and the serum HDL-C level was significantly increased (P < 0.05) compared with AC/GQD alone. AST and ALT activities treated with both GQD and AC+GQD group were significantly reduced (P < 0.05) compared with AC group. There was a significant difference in the pharmacokinetic parameters of midazolam between control and GQD groups (P < 0.05). Maximum concentration (C_max), area under the concentration-time curve (AUC) from time 0 to the last quantifiable concentration (AUC_0-t) and AUC from time 0 to infinity (AUC_0-∞) increased significantly in GQD group.

CONCLUSIONS

The result suggested that GQD combined with AC can improve the lipid-lowering effect of AC and reduce the damage of AC to the liver simultaneously. However, GQD can inhibit the activity of CYP3A2 in hyperlipidemic rats and increase the blood concentration of AC. Therefore, the clinical dose of AC should be adjusted when they are combined. Since the study was conducted in rats,  further research should be carried out to assess the uniformity of the pharmacokinetics and pharmacodynamics between rats and humans.

Drug-drug interactions induced by Linderane based on mechanism-based inactivation of CYP2C9 and the molecular mechanisms

Linderane (LDR) is a main furan-containing sesquiterpenoid of the common herbal medicine Lindera aggregata (Sims) Kosterm. Our early study indicated that LDR led to mechanism-based inactivation (MBI) of CYP2C9 in vitro, implying possible drug-drug interactions (DDIs) in clinic. In the present study, influence of LDR on the pharmacokinetics of the corresponding hydroxylated metabolites of CYP2C9 substrates in rats was investigated. Pharmacokinetic studies revealed that pretreatment with LDR at 20 mg/kg for 15 days inhibited the metabolism of both tolbutamide and warfarin catalyzed by CYP2C9. As for 4-hydroxytolbutamide, the C_max was decreased, the t_1/2z was prolonged, and the Vz/F was increased, all with significant difference. As for 7-hydroxywarfarin, the AUC_0-t/AUC_0-∞ and CLz/F were significantly decreased and increased, respectively. Furthermore, the underlying molecular mechanisms based on MBI of CYP2C9 by LDR were revealed. Two reactive metabolites of LDR, furanoepoxide and γ-ketoenal intermediates were identified in CYP2C9 recombinant enzyme incubation systems. Correspondingly, covalent modifications of lysine and cysteine residues of CYP2C9 protein were discovered in the CYP2C9 incubation system treated with LDR. The formation of protein adducts exhibited obvious time- and dose-dependence, which is consistent with the trend of enzyme inhibition caused by LDR in vitro. In addition to the apoprotein of CYP2C9, the heme content was significantly reduced after co-incubation with LDR. These data revealed that modification of both apoprotein and heme of CYP2C9 by reactive metabolites of LDR led to MBI of CYP2C9, therefore resulting in the inhibition of biotransformation of CYP2C9 substrates to their corresponding metabolites in vivo.

Immune-Related Gene Polymorphisms and Pharmacogenetic Studies in Nephrology

A large subgroup of patients with chronic kidney disease still encounter serious adverse effects and lack of responsiveness to medications, possibly because of the interindividual genetic variability in genes involved in the metabolism and transport of the treatments used. As a consequence, several pharmacogenetic studies have been conducted in nephrology patients that examine the effect of genetic variants in response to treatment in kidney diseases. The present commentary focuses on immune-related genes (TNF [tumor necrosis factor], MIF [macrophage migration inhibitory factor], and IL-10 [interleukin 10]) or those genes that may regulate the response to immunosuppressive medications (ABCB1 [ATP binding cassette subfamily B member 1] and ITPA [inosine triphosphatase]) used in kidney diseases. These genes were selected from those showing significant results in a recent meta-analysis of pharmacogenetic studies of patients with chronic kidney disease. This commentary highlights that certain polymorphisms should be investigated in patients with kidney diseases, especially if they are to be administered immunosuppressive agents. In certain cases, flavonoids such as quercetin may be beneficial.

Role of Phytochemicals in Cancer Chemoprevention: Insights

Cancer is a condition where the body cells multiply in an uncontrollable manner. Chemoprevention of cancer is a broad term that describes the involvement of external agents to slow down or suppress cancer growth. Synthetic and natural compounds are found useful in cancer chemoprevention. The occurrence of global cancer type varies, depending on many factors such as environmental, lifestyle, genetic etc. Cancer is often preventable in developed countries with advanced treatment modalities, whereas it is a painful death sentence in developing and low-income countries due to the lack of modern therapies and awareness. One best practice to identify cancer control measures is to study the origin and risk factors associated with common types. Based on these factors and the health status of patients, stage, and severity of cancer, type of treatment is decided. Even though there are well-established therapies, cancer still stands as one of the major causes of death and a public health burden globally. Research shows that most cancers can be prevented, treated, or the incidence can be delayed. Phytochemicals from various medicinal plants were reported to reduce various risk factors associated with different types of cancer through their chemopreventive role. This review highlights the role of bioactive compounds or natural products from plants in the chemoprevention of cancer. There are many plant based dietary factors involved in the chemoprevention process. The review discusses the process of carcinogenesis and chemoprevention using plants and phytocompounds, with special reference to five major chemopreventive phytocompounds. The article also summarizes the important chemopreventive mechanisms and signaling molecules involved in the process. Since the role of antioxidants in chemoprevention is inevitable, an insight into plant-based antioxidant compounds that fight against this dreadful disease at various stages of carcinogenesis and disease progression is discussed. This will fill the research gap in search of chemopreventive natural compounds and encourage scientists in clinical trials of anticancer agents from plants.

Flecainide toxicity associated with the use of goji berries: a case report

Background

Goji berries (GB), usually marketed as a 'superfruit', are a widely used herbal supplement. As with other herbal remedies, the use of GB might be associated with herb-drug interactions, increasing plasma levels of other drugs and causing adverse events. Here, we present the case of a patient that developed flecainide toxicity secondary to an herb-drug interaction, associated with the use of GB to prevent COVID-19.

Case summary

A 75-year-old female presented to the emergency department with fainting. She was taking flecainide for the treatment of atrial extrasystoles diagnosed 2 years previously, and she was using a tea of GB for the prevention of COVID-19. The admission electrocardiogram showed a wide complex polymorphic tachycardia that was considered and treated as flecainide toxicity. The patient had a favourable evolution and was discharged 48 h after admission.

Discussion

Flecainide toxicity is uncommon and needs timely recognition and treatment; it is usually secondary to overdose and renal or hepatic failure. In our case, toxicity was associated with GB use, probably by inhibition of CYP2D6 which is the main enzyme associated with the metabolism of flecainide. Clinicians need to be aware of the possible interactions between herbal remedies (in this case used for the prevention of COVID-19) and cardiovascular drugs that are used to treat chronic cardiovascular diseases.

Insights into oral bioavailability enhancement of therapeutic herbal constituents by cytochrome P450 3A inhibition

Herbal plants typically have complex compositions and diverse mechanisms. Among them, bioactive constituents with relatively high exposure in vivo are likely to exhibit therapeutic efficacy. On the other hand, their bioavailability may be influenced by the synergistic effects of different bioactive components. Cytochrome P450 3A (CYP3A) is one of the most abundant CYP enzymes, responsible for the metabolism of 50% of approved drugs. In recent years, many therapeutic herbal constituents have been identified as CYP3A substrates. It is more evident that CYP3A inhibition derived from the herbal formula plays a critical role in improving the oral bioavailability of therapeutic constituents. CYP3A inhibition may be the mechanism of the synergism of herbal formula. In this review, we explored the multiplicity of CYP3A, summarized herbal monomers with CYP3A inhibitory effects, and evaluated herb-mediated CYP3A inhibition, thereby providing new insights into the mechanisms of CYP3A inhibition-mediated oral herb bioavailability.

Naturally occurring coumestans from plants, their biological activities and therapeutic effects on human diseases

Naturally occurring coumestans are known as a collection of plant-derived polycyclic aromatic secondary metabolites which are characterized by the presence of an oxygen heterocyclic four-ring system comprising a coumarin moiety and a benzofuran moiety sharing a C˭C bond. Recently, there is an increasing attention in excavating the medicinal potential of coumestans, particularly coumestrol, wedelolactone, psoralidin and glycyrol, in a variety of diseases. This review is a comprehensive inventory of the chemical structures of coumestans isolated from various plant sources during the period of 1956-2020, together with their reported biological activities. 120 molecules were collected and further classified as coumestans containing core skeleton, dimethylpyranocoumestans, furanocoumestans, O-glycosylated coumestans and others, which showed a wide range of pharmacological activities including estrogenic, anti-cancer, anti-inflammatory, anti-osteoporotic, organ protective, neuroprotective, anti-diabetic and anti-obesity, antimicrobial, immunosuppressive, antioxidant and skin-protective activities. Furthermore, this review focuses on the counteraction of coumestans against bone diseases and organ damages, and the involved molecular mechanisms, which could provide important information to better understand the medicinal values of these compounds. This review is intended to be instructive for the rational design and development of less toxic and more effective drugs with a coumestan scaffold.

Effects of saikosaponin-d on CYP3A4 in HepaRG cell and protein-ligand docking study

Saikosaponin-d (SSd) is a major bioactive triterpenoid saponin extracted from Bupleurum, which has anti-inflammatory, anticancer, antioxidative and anti-hepatic fibrosis effects. Due to the effects of Bupleurum-related formulations on cytochrome P450 (CYPs) expression still remain unclear, the combination therapies involved formulations containing Bupleurum may sometimes lead to unexpected drug-drug interactions in clinical practice. These interactions can limit the clinical applications of related formulations. In this study, we tried to explore the effects of SSd on CYP3A4 mRNA, protein expression and the enzyme activity in HepaRG cells by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), Western blot (WB) and HPLC method, respectively. The interaction between SSd and CYP3A4 was analysed by molecular docking. HepaRG cells were cultured with different concentrations of SSd (0.5, 1, 5 and 10 μmol/L) for 72 hours. It is revealed that SSd can inhibit CYP3A4 mRNA and its protein expression, and also the enzyme activity. Molecular docking study demonstrated that SSd can bind to several key active sites of amino acid residues of CYP3A4 protein with hydrogen bonds and hydrophobic interactions. Thus, drug-drug interactions resulted by SSd inhibiting CYP3A4 need attention when formulations containing SSd or Bupleurum are co-administrated with drugs metabolized by CYP3A4.

Mechanism-based inactivation of cytochrome P450 enzymes by natural products based on metabolic activation

Cytochrome P450 enzymes (P450 enzymes) are the most common and important phase I metabolic enzymes and are responsible for the majority of the metabolism of clinical drugs and other xenobiotics. Drug-drug interactions (DDIs) can occur when the activities of P450 enzymes are inhibited. In particular, irreversible inhibition of P450 enzymes may lead to severe adverse interactions, compared to reversible inhibition. Many natural products have been shown to be irreversible inhibitors of P450 enzymes. The risks for intake of naturally occurring irreversible P450 enzyme inhibitors have been rising due to the rapid growth of the global consumption of natural products. Irreversible inhibition is usually called mechanism-based inactivation, which is time-, concentration- and NADPH- dependent. Generally, the formation of electrophilic intermediates is fundamental for the inactivation of P450 enzymes. This review comprehensively classifies natural P450 enzyme inactivators, including terpenoids, phenylpropanoids, flavonoids, alkaloids, and quinones obtained from herbs or foods. Moreover, the structure - activity correlations according to the IC₅₀ (or K_i) values reported in the literature as well as the underlying mechanisms based on metabolic activation are highlighted in depth.

Comparison of CYP2C9 Activity in Ethiopian and Non-Ethiopian Jews Using Phenytoin as a Probe

The pharmacokinetics of CYP2C9 substrates is characterized by substantial interethnic variability. The objective of the study was to compare CYP2C9 activity by using Phenytoin Metabolic Ratio (PMR) between Ethiopian and non-Ethiopian Jews. PMR was derived from the ratio of p-HPPH in 24 h urine collection to plasma phenytoin, 12 h (PMR24/12) or 24 h (PMR24/24) after the administration of 300 mg phenytoin. Analysis of CYP2C9*2, *3, *5, *6, *8, and *11 was carried by direct sequencing. PMR was significantly correlated with CYP2C9 genotype in both groups (p < 0.002). Mean PMR values were similar among Ethiopians and non-Ethiopians despite the fact that the fraction of non-carriers of CYP2C9 variant alleles was significantly different (85 vs. 53%, respectively, p < 0.001). However, among non-carriers of CYP2C9*2, *3, *5, *6, *8, and *11 variant alleles, PMR24/12 and PMR24/24 values were 30 and 34% greater respectively in the non-Ethiopians group (p < 0.001). In conclusion-CYP2C9 activity as measured by PMR is similar in Ethiopian and non-Ethiopian Jews. However, among non-carriers of CYP2C9 variant alleles accounting for 85% of Ethiopian Jews, CYP2C9 activity is decreased by approximately one third as compared with non-Ethiopian Jews. Unique genetic CYP2C9 polymorphisms occurring only in Ethiopians may account for this difference.