Metabolic interactions between acetaminophen (paracetamol) and two flavonoids, luteolin and quercetin, through in-vitro inhibition studies

Effects of three flavonoids on the metabolism of lenvatinib

Lenvatinib is a first-line therapy for the treatment of hepatocellular carcinoma (HCC), an active multi-target tyrosine kinase inhibitor (TKI). The interaction between Traditional Chinese Medicine (TCM) and chemicals has increasingly become a research hotspot. The objective of this study was to pinpoint the effects of three flavonoids on the metabolism of lenvatinib. Enzyme reaction system was established and optimized in vitro, and in vivo experiments were conducted in Sprague-Dawley (SD) rats, where the analytes were detected by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). We found that among three flavonoids, luteolin and myricetin had strong inhibitory effects on lenvatinib metabolism, with half-maximal inhibitory concentration (IC50) values of 11.36 ± 0.46 µM and 11.21 ± 0.81 µM in rat liver microsomes (RLM), respectively, and 6.89 ± 0.43 µM and 12.32 ± 1.21 µM in human liver microsomes (HLM), respectively. In Sprague-Dawley rats, the combined administration of lenvatinib and luteolin obviously expanded the exposure to lenvatinib; however, co-administered with myricetin did not have any changes, which may be due to the poor bioavailability of myricetin in vivo. Furthermore, the inhibitory type of luteolin on lenvatinib showed an un-competitive in RLM and a mixed in HLM. Collectively, flavonoids with liver protection, especially luteolin, may inhibit lenvatinib metabolism in vitro and in vivo.

Luteolin: A promising multifunctional natural flavonoid for human diseases

Natural products are closely associated with human health. Luteolin (LUT), a flavonoid polyphenolic compound, is widely found in fruits, vegetables, flowers, and herbs. It is noteworthy that LUT exhibits a variety of beneficial pharmacological properties and holds significant potential for clinical applications, particularly in antitumor, anti-convulsion, diabetes control, anti-inflammatory, neuroprotection, anti-oxidation, anti-cardiovascular, and other aspects. The potential mechanism of action has been partially elucidated, including the mediation of NF-κB, toll-like receptor, MAPK, Wnt/β-catenin, PI3K/Akt, AMPK/mTOR, and Nrf-2, among others. The review that aimed to comprehensively consolidate essential information on natural sources, pharmacological effects, therapeutic and preventive potential, as well as potential mechanisms of LUT. The objective is to establish a theoretical basis for the continued development and application of LUT.

Hepatoprotective Effects of Flavonoids against Benzo[a]Pyrene-Induced Oxidative Liver Damage along Its Metabolic Pathways

Benzo[a]pyrene (B[a]P), a highly carcinogenic polycyclic aromatic hydrocarbon primarily formed during incomplete organic matter combustion, undergoes a series of hepatic metabolic reactions once absorbed into the body. B[a]P contributes to liver damage, ranging from molecular DNA damage to the onset and progression of various diseases, including cancer. Specifically, B[a]P induces oxidative stress via reactive oxygen species generation within cells. Consequently, more research has focused on exploring the underlying mechanisms of B[a]P-induced oxidative stress and potential strategies to counter its hepatic toxicity. Flavonoids, natural compounds abundant in plants and renowned for their antioxidant properties, possess the ability to neutralize the adverse effects of free radicals effectively. Although extensive research has investigated the antioxidant effects of flavonoids, limited research has delved into their potential in regulating B[a]P metabolism to alleviate oxidative stress. This review aims to consolidate current knowledge on B[a]P-induced liver oxidative stress and examines the role of flavonoids in mitigating its toxicity.

Harder, better, faster, stronger? Retrospective chart review of adverse events of interactions between adaptogens and antidepressant drugs

Aim: We aimed to systematically evaluate the prevalence and clinical characteristics of adverse events associated with the adaptogens and antidepressant drug interactions in a retrospective chart review. Methodology: A total of 1,816 reports of adverse events were evaluated. Cases were included in the analysis if the pharmacoepidemiological analysis showed the presence of a high probability of a causal relationship between an adaptogen and antidepressant interaction and the occurrence of adverse events. The following data were extracted from the reports: age, sex, antidepressant, plant products containing adaptogens, other concomitant medications, and clinical consequences of the interactions and their possible mechanisms. Results: Adaptogens were involved in 9% of adverse events associated with the concomitant use of antidepressants and other preparations. We identified 30 reports in which side effects presented a causal relationship with the use of antidepressants and adaptogens. Here, we present the list of adaptogens with the corresponding antidepressants and the side effects caused by their interactions: Withania somnifera: reboxetine (testicle pain and ejaculatory dysfunctions), sertraline (severe diarrhea), escitalopram (myalgia, epigastric pain, nausea, vomiting, restless legs syndrome, and severe cough), and paroxetine (generalized myalgia, ophthalmalgia, and ocular hypertension); Eleutherococcus senticosus: duloxetine (upper gastrointestinal bleeding), paroxetine (epistaxis), sertraline (vaginal hemorrhage), and agomelatine (irritability, agitation, headache, and dizziness); Schisandra chinensis: bupropion (arthralgia and thrombocytopenia), amitriptyline (delirium), and fluoxetine (dysuria); Tribulus terrestris: citalopram (generalized pruritus), escitalopram (galactorrhea), and trazodone (psoriasis relapse); Coptis chinensis: mianserin (arrhythmias), mirtazapine (edema of lower limbs and myalgia), and fluoxetine (gynecomastia); Cimicifuga racemosa: mianserin (restless legs syndrome), paroxetine (gynecomastia and mastalgia), and venlafaxine (hyponatremia); Bacopa monnieri: agomelatine (back pain and hyperhidrosis) and moclobemide (myocardial infarction); Gynostemma pentaphyllum: duloxetine (back pain); Cordyceps sinensis: sertraline (upper gastrointestinal bleeding); Lepidium meyenii: mianserin (restless legs syndrome); and Scutellaria baicalensis: bupropion (seizures). Conclusion: Clinicians should monitor the adverse events associated with the concomitant use of adaptogens and antidepressant drugs in patients with mental disorders. Aggregation of side effects and pharmacokinetic interactions (inhibition of CYP and p-glycoprotein) between those medicines may result in clinically significant adverse events.

Luteolin and Vernodalol as Bioactive Compounds of Leaf and Root Vernonia amygdalina Extracts: Effects on α-Glucosidase, Glycation, ROS, Cell Viability, and In Silico ADMET Parameters

The aqueous decoctions of Vernonia amygdalina (VA) leaves and roots are widely used in traditional African medicine as an antidiabetic remedy. The amount of luteolin and vernodalol in leaf and root extracts was detected, and their role was studied regarding α-glucosidase activity, bovine serum albumin glycation (BSA), reactive oxygen species (ROS) formation, and cell viability, together with in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. Vernodalol did not affect α-glucosidase activity, whereas luteolin did. Furthermore, luteolin inhibited the formation of advanced glycation end products (AGEs) in a concentration-dependent manner, whereas vernodalol did not reduce it. Additionally, luteolin exhibited high antiradical activity, while vernodalol demonstrated a lower scavenger effect, although similar to that of ascorbic acid. Both luteolin and vernodalol inhibited HT-29 cell viability, showing a half-maximum inhibitory concentration (IC₅₀) of 22.2 µM (-Log IC₅₀ = 4.65 ± 0.05) and 5.7 µM (-Log IC₅₀ = 5.24 ± 0.16), respectively. Finally, an in silico ADMET study showed that both compounds are suitable candidates as drugs, with appropriate pharmacokinetics. This research underlines for the first time the greater presence of vernodalol in VA roots compared to leaves, while luteolin is prevalent in the latter, suggesting that the former could be used as a natural source of vernodalol. Consequently, root extracts could be proposed for vernodalol-dependent antiproliferative activity, while leaf extracts could be suggested for luteolin-dependent effects, such as antioxidant and antidiabetic effects.

Interaction of luteolin, naringenin, and their sulfate and glucuronide conjugates with human serum albumin, cytochrome P450 (CYP2C9, CYP2C19, and CYP3A4) enzymes and organic anion transporting polypeptide (OATP1B1 and OATP2B1) transporters

Luteolin and naringenin are flavonoids found in various foods/beverages and present in certain dietary supplements. After a high intake of these flavonoids, their sulfate and glucuronide conjugates reach micromolar concentrations in the bloodstream. Some pharmacokinetic interactions of luteolin and naringenin have been investigated in previous studies; however, only limited data are available in regard to their metabolites. In this study, we aimed to investigate the interactions of the sulfate and glucuronic acid conjugates of luteolin and naringenin with human serum albumin, cytochrome P450 (CYP2C9, 2C19, and 3A4) enzymes, and organic anion transporting polypeptide (OATP1B1 and OATP2B1) transporters. Our main findings are as follows: (1) Sulfate conjugates formed more stable complexes with albumin than the parent flavonoids. (2) Luteolin and naringenin conjugates showed no or only weak inhibitory action on the CYP enzymes examined. (3) Certain conjugates of luteolin and naringenin are potent inhibitors of OATP1B1 and/or OATP2B1 enzymes. (4) Conjugated metabolites of luteolin and naringenin may play an important role in the pharmacokinetic interactions of these flavonoids.

Effect of quercetin on the pharmacokinetics of selexipag and its active metabolite in beagles

CONTEXT

As an inhibitor cytochrome P450 family 2 subfamily C polypeptide 8 (CYP2C8), quercetin is a naturally occurring flavonoid with its glycosides consumed at least 100 mg per day in food. However, it is still unknown whether quercetin and selexipag interact.

OBJECTIVE

The study investigated the effect of quercetin on the pharmacokinetics of selexipag and ACT-333679 in beagles.

MATERIALS AND METHODS

The ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to investigate the pharmacokinetics of orally administered selexipag (2 mg/kg) with and without quercetin (2 mg/kg/day for 7 days) pre-treatment in beagles. The effect of quercetin on the pharmacokinetics of selexipag and its potential mechanism was studied through the pharmacokinetic parameters.

RESULTS

The assay method was validated for selexipag and ACT-333679, and the lower limit of quantification for both was 1 ng/mL. The recovery and the matrix effect of selexipag were 84.5-91.58% and 94.98-99.67%, while for ACT-333679 were 81.21-93.90% and 93.17-99.23%. The UPLC-MS/MS method was sensitive, accurate and precise, and had been applied to the herb-drug interaction study of quercetin with selexipag and ACT-333679. Treatment with quercetin led to an increased in C_max and AUC_0-t of selexipag by about 43.08% and 26.92%, respectively. While the ACT-333679 was about 11.11% and 18.87%, respectively.

DISCUSSION AND CONCLUSION

The study indicated that quercetin could inhibit the metabolism of selexipag and ACT-333679 when co-administration. Therefore, the clinical dose of selexipag should be used with caution when co-administered with foods high in quercetin.

Evaluation of the inhibitory effect of quercetin on the pharmacokinetics of tucatinib in rats by a novel UPLC-MS/MS assay

CONTEXT

Tucatinib (CYP2C8 substrate) and quercetin (CYP2C8 inhibitor) are two common drugs for the treatment of cancer. However, the effect of quercetin on the metabolism of tucatinib remains unknown.

OBJECTIVE

We validated a sensitive method to quantify tucatinib levels in rat plasma based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), which was successfully employed to explore the effect of quercetin on tucatinib pharmacokinetics in rats.

MATERIALS AND METHODS

An Acquity UPLC BEH C18 column was applied to achieve the separation of tucatinib and internal standard (IS) talazoparib after protein precipitation with acetonitrile. Then, we used this assay to investigate the effect of different doses of quercetin (25, 50 and 100 mg/kg) on the exposure of orally administered tucatinib (30 mg/kg) in 24 Sprague-Dawley (SD) rats, which were randomly divided into three quercetin pre-treated groups and one control group (n = 6).

RESULTS

Our developed assay was verified in all aspects of bioanalytical method validation, involving lower limit of quantification (LLOQ), selectivity, accuracy and precision, calibration curve, extraction recovery, matrix effect and stability. After pre-treatment with 100 mg/kg quercetin, AUC_0→t, AUC_0→∞ and C_max of tucatinib were remarkably increased by 75.4%, 75.8% and 59.1% (p < 0.05), respectively, while CLz/F was decreased significantly by 47.3% (p < 0.05) when compared with oral administration of 30 mg/kg tucatinib alone. This change is dose-dependent.

CONCLUSIONS

This study will help better understand the pharmacokinetic properties of tucatinib with concurrent use with quercetin, and more clinical verifications were inspired to confirm whether this interaction has clinical significance in humans.

Studies on Chemical Characterization of Ginkgo Amillaria Oral Solution and Its Drug–Drug Interaction With Piceatannol 3′-O-β-D-Glucopyranoside for Injection

Ginkgo Amillaria oral solution (GAO) is commonly used for the treatment of cardiovascular and cerebrovascular diseases in China. Piceatannol-3′-O-β-D-glucopyranoside for injection (PGI) is mainly used for the prevention and treatment of ischemic cerebrovascular diseases. With the spread of cerebrovascular disease, the possibility of combining the two drugs has increased; however, there is no research on the drug–drug interaction (DDI) between these two medicines. In this paper, an ultrahigh-performance liquid chromatography/quadrupole–orbitrap mass spectrometry (UHPLC/Q-Orbitrap MS) method was established to characterize the chemical constituents of GAO first; 62 compounds were identified or tentatively identified based on their retention time (RT), MS, and MS/MS data. Nine main compounds were determined by ultrahigh-performance liquid chromatography/triple quadrupole mass spectrometry (UPLC-QQQ-MS). Furthermore, incubation with liver microsomes in vitro was fulfilled; the results showed that GAO had a significant inhibitory effect on UGT1A9 and UGT2B7 (p < 0.05), and PGI was mainly metabolized by UGT1A9. The identification results of in vivo metabolites of PGI showed that PGI mainly undergoes a phase II binding reaction mediated by UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) in vivo. Therefore, pharmacokinetic studies were performed to investigate the DDI between GAO and PGI. The results showed that the AUC (p < 0.05) and T_1/2 (p < 0.05) of PGI in vivo were significantly increased when administered together with GAO, whereas the CL was significantly decreased (p < 0.05). The exploration of in vitro and in vivo experiments showed that there was a DDI between GAO and PGI.

Protective effect of luteolin against chemical and natural toxicants by targeting NF-κB pathway

Humans are continuously exposed to environmental, occupational, consumer and household products, food, and pharmaceutical substances. Luteolin, a flavone from the flavonoids family of compounds, is found in different fruits and vegetables. LUT is a strong anti-inflammatory (via inhibition of NF-κB, ERK1/2, MAPK, JNK, IL-6, IL-8, and TNF-α) and antioxidant agent (reducing ROS and enhancement of endogenous antioxidants). LUT can chelate transition metal ions responsible for ROS generation and consequently repress lipoxygenase. It has been proven that NF-κB, as a commom cellular pathway plays a considerable role in the progression of inflammatory process and stimulates the expression of genes encoding inducible pro-inflammatory enzymes (iNOS and COX-2) and cytokines including IL-1β, IL-6, and TNF-α. This review summarizes the available literature discussing LUT and its potential protective role against pharmaceuticals-, metals-, and environmental compounds-induced toxicities. Furthermore, the review explains the involved protective mechanisms, especially inhibition of the NF-κB pathway.

Effects of the total flavonoid extracts and the monomers of Daphne genkwa on CYP2C8 activity

1. This study aimed to assess the effects of total flavonoid extracts (TFDG) and the monomers of Daphne genkwa on the CYP2C8 activity in vitro and in vivo.2. The 50% inhibitory concentration (IC₅₀) values were used to determine the inhibitory effect of TFDG and its four monomers for the CYP2C8 activity by recombinant human CYP2C8 (RHCYP2C8) yeast microsome system in vitro, and the volume per dose index (VDI) was predicted the potential inhibition in vivo. The effects of multiple-dose administration of TFDG on the pharmacokinetic parameters of rosiglitazone in rats were evaluated.3. The IC₅₀ values of apigenin, luteolin, hydroxy-genkwanin, genkwanin, and TFDG were 7.27μmol/L, 11.9μmol/L, 28.1μmol/L, 127μmol/L, and 13.4μg/mL, respectively. The VDI values of apigenin and TFDG were 2.15L and 6.60L. In vivo study, compared with the control group, the elimination phase half-life and mean residence time in the TFDG treatment group were significantly increased by 96.9% and 106.8% (p < 0.05), respectively.4. Apigenin showed a moderate inhibitory effect on the CYP2C8 activity in vitro, while the other three monomers were weak inhibitors. TFDG had a strong inhibitory effect on CYP2C8 in vitro and in vivo, and also inhibited the metabolism of rosiglitazone in rats.

Can nutraceuticals assist treatment and improve covid-19 symptoms?

Viral diseases have always played an important role in public and individual health. Since December 2019, the world is facing a pandemic of SARS-CoV-2, a coronavirus that results in a syndrome known as COVID-19. Several studies were conducted to implement antiviral drug therapy, until the arrival of SARS-CoV-2 vaccines. Numerous scientific investigations have considered some nutraceuticals as an additional treatment of COVID-19 patients to improve their clinical picture. In this review, we would like to emphasize the studies conducted to date about this issue and try to understand whether the use of nutraceuticals as a supplementary therapy to COVID-19 may be a valid and viable avenue. Based on the results obtained so far, quercetin, astaxanthin, luteolin, glycyrrhizin, lactoferrin, hesperidin and curcumin have shown encouraging data suggesting their use to prevent and counteract the symptoms of this pandemic infection.

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.

Ginkgo biloba L. flavonoids inhibit CYP 2A5; potential dietary supplement for nicotine replacement therapy enhancement

Smoking is a public health concern, and even though smoking cessation methods exist, nicotine replacement therapy (NRT) is often ineffective. Smoking behavior is related to the nicotine metabolizing enzyme (NME) P450 2A6 (mouse 2A5) polymorphisms. Accordingly, fast metabolizers are nicotine dependent, and have low quitting rates compared to slow metabolizers. In this study we examined the ability of Ginkgo biloba L (GB) and its constituents to inhibit the NME, using mouse liver microsomes containing the 2A5 enzyme. Our results indicate that GB can inhibit 2A5 (25% inhibition at 5%v/v), with the flavonoids quercetin, isorhamnetin, and kaempferol being responsible for this inhibition (23.5%, 10.7%, 25.2% inhibition at 60 ng/μL, respectively). Importantly, the flavonoids inhibited 2A5 via mechanism based inhibition (for quercetin 30 ng/μl inhibition increased from 20.8% to 26.9% within 15 minutes). Our results suggest that GB if consumed on a regular basis can help NRT enhancement particularly in fast nicotine metabolizers.

Hepatoprotective effect of kaempferol glycosides isolated from Cedrela odorata L. leaves in albino mice: involvement of Raf/MAPK pathway

Background and purpose:

Paracetamol is the most implicated xenobiotic in inducing hepatotoxicity. Our study aimed to determine the impact of some kaempferol glycosides isolated from the leaves of Cedrela odorata L. on paracetamol hepatotoxicity.

Experimental approach:

The methanolic extract of dried leaves of C. odorata L. was subjected to the combination of spectroscopic methods (¹H and ¹³CNMR). Six kaempferol glycosides were isolated: kaempferol-3-O-β-D-glycopyranoside (astragalin), kaempferol-3-O-β-L-rhamnopyranoside, kaempferol-3-O-β-D-rutinoside, kaempferide-3-O-β-D-rutinoside, kaempferide-3-O-β-Drutinosyl-7-O-β-D-rhamnopyranoside, and kaempferol-3-O-β-D- rutinosyl-7-O-a-D-arabinopyranoside. Fifty-four female Swiss Albino mice were divided randomly into 9 groups including (1) control negative (1 mL/kg saline; IP), (2) control positive (paracetamol 300 mg/kg; IP), (3) silymarin 50 mg/kg (IP). Animals of groups 4-9 were injected with 6 different samples of isolated compounds at 100 mg/kg (IP). One h later, groups 3-9 were injected with paracetamol (300 mg/kg IP). Two h later, tissue samples were taken from all animals to assess nitrotyrosine, c-Jun N-terminal protein kinase (c-JNK), Raf -1kinase, and oxidative stress biomarkers viz. reduced glutathione (GSH) and malondialdehyde (MDA).

Findings/Results:

Isolated glycosides had a prominent anti-apoptotic effect via inhibition of c-JNK and Raf-1 kinase. They also exerted a powerful antioxidant effect by modulating the oxidative stress induced by paracetamol via increasing GSH, reducing MDA and nitrotyrosine concentrations compared to positive control. The glycoside (1) showed a better effect than silymarin (standard) in ameliorating the formation of nitrotyrosine, Raf-1 kinase, c-JNK, and GSH.

Conclusion and implication:

Kaempferol glycosides isolated for the first time from C. odorata L. leaves exerted antioxidant and antiapoptotic effects via amelioration of oxidative stress and inhibition of Raf/MAPK pathway.

The Impact of Diet and Exercise on Drug Responses

It is well known that lifestyle changes can alter several physiological functions in the human body. For exercise and diet, these effects are used sensibly in basic therapies, as in cardiovascular diseases. However, the physiological changes induced by exercise and a modified diet also have the capacity to influence the efficacy and toxicity of several drugs, mainly by affecting different pharmacokinetic mechanisms. This pharmacological plasticity is not clinically relevant in all cases but might play an important role in altering the effects of very common drugs, particularly drugs with a narrow therapeutic window. Therefore, with this review, we provide insights into possible food–drug and exercise–drug interactions to sharpen awareness of the potential occurrence of such effects.

Protective Effect of Phoenix dactylifera L. Seeds against Paracetamol-Induced Hepatotoxicity in Rats: A Comparison with Vitamin C

Phoenix dactylifera L. (date palm) seeds have been mentioned in the Moroccan pharmacopoeia as efficient remedies against a wide range of diseases including hepatic and gastrointestinal disorders and countless infections. The current work was performed to assess the phenolic profile and hepatoprotective potential of two date seed varieties, locally known as Jihl and Majhoul, aqueous extracts against paracetamol- (PCM-) driven liver toxicity in 42 Wistar rats. The polyphenol profile was built by means of an HPLC analysis. Hepatic damage was provoked by exposing rats to PCM at a dose of 1.5 g/kg once a week. Besides PCM, Jihl and Majhoul date seed extracts (200 and 400 mg/kg) were administered orally in a day-to-day routine. Our findings showed that among the examined polyphenol compounds, p-coumaric acid, quercetin, caffeic acid, and rutin were the most abundant phytochemicals. Date pits significantly (p < 0.001) stabilized the PCM-driven alterations in liver function parameters (AST, ALT, ALP, LDH, total protein, direct bilirubin, and total bilirubin). Moreover, Phoenix dactylifera pits enhanced considerably (p < 0.001) the activities of antioxidant enzymes (SOD, CAT, and GPx) as well as the level of reduced glutathione (GSH). The established hepatoprotective effect may be due to the date seeds antioxidant effect and their ability to trap free radicals. The main outcomes of the present study could validate the traditional use of these date seeds to manage various health conditions.

Human Lanosterol 14-Alpha Demethylase (CYP51A1) Is a Putative Target for Natural Flavonoid Luteolin 7,3'-Disulfate

Widespread pathologies such as atherosclerosis, metabolic syndrome and cancer are associated with dysregulation of sterol biosynthesis and metabolism. Cholesterol modulates the signaling pathways of neoplastic transformation and tumor progression. Lanosterol 14-alpha demethylase (cytochrome P450(51), CYP51A1) catalyzes one of the key steps in cholesterol biosynthesis. The fairly low somatic mutation frequency of CYP51A1, its druggability, as well as the possibility of interfering with cholesterol metabolism in cancer cells collectively suggest the clinical importance of CYP51A1. Here, we show that the natural flavonoid, luteolin 7,3'-disulfate, inhibits CYP51A1 activity. We also screened baicalein and luteolin, known to have antitumor activities and low toxicity, for their ability to interact with CYP51A1. The Kd values were estimated using both a surface plasmon resonance optical biosensor and spectral titration assays. Unexpectedly, in the enzymatic activity assays, only the water-soluble form of luteolin-luteolin 7,3'-disulfate-showed the ability to potently inhibit CYP51A1. Based on molecular docking, luteolin 7,3'-disulfate binding suggests blocking of the substrate access channel. However, an alternative site on the proximal surface where the redox partner binds cannot be excluded. Overall, flavonoids have the potential to inhibit the activity of human CYP51A1 and should be further explored for their cholesterol-lowering and anti-cancer activity.

Drug-herb interactions between Scutellaria baicalensis and pharmaceutical drugs: Insights from experimental studies, mechanistic actions to clinical applications

Whilst the popular use of herbal medicine globally, it poses challenges in managing potential drug-herb interaction. There are two folds of the drug-herb interaction, a beneficial interaction that may improve therapeutic outcome and minimise the toxicity of drug desirably; by contrast, negative interaction may evoke unwanted clinical consequences, especially with drugs of narrow therapeutic index. Scutellaria baicalensis Georgi is one of the most popular medicinal plants used in Asian countries. It has been widely used for treating various diseases and conditions such as cancer, diabetes, inflammation, and oxidative stress. Studies on its extract and bioactive compounds have shown pharmacodynamic and pharmacokinetic interactions with a wide range of pharmaceutical drugs as evidenced by plenty of in vitro, in vivo and clinical studies. Notably, S. baicalensis and its bioactives including baicalein, baicalin and wogonin exhibited synergistic interactions with many pharmaceutical drugs to enhance their efficacy, reduce toxicity or overcome drug resistance to combat complex diseases such as cancer, diabetes and infectious diseases. On the other hand, S. baicalensis and its bioactives also affected the pharmacokinetic profile of many drugs in absorption, distribution, metabolism and elimination via the regulatory actions of the efflux pumps and cytochrome P450 enzymes. This review provides comprehensive references of the observed pharmacodynamic and pharmacokinetic drug interactions of Scutellaria baicalensis and its bioactives. We have elucidated the interaction with detailed mechanistic actions, identified the knowledge gaps for future research and potential clinical implications. Such knowledge is important for the practice of both conventional and complementary medicines, and it is essential to ensure the safe use of related herbal medicines. The review may be of great interest to practitioners, consumers, clinicians who require comprehensive information on the possible drug interactions with S. baicalensis and its bioactives.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Flavones as a Privileged Scaffold in Drug Discovery: Current Developments

BACKGROUND

Flavones are one of the main subclasses of flavonoids with diverse pharmacological properties. They have been reported to possess antimalarial, antimicrobial, anti-tuberculosis, anti-allergic, antioxidant, anti-inflammatory activities, among others.

OBJECTIVE

The present review summarizes the recent information on the pharmacological properties of naturally occurring and synthetic flavones.

METHODS

Scientific publications referring to natural and synthetic flavones in relation to their biological activities were hand-searched in databases such as SciFinder, PubMed (National Library of Medicine), Science Direct, Wiley, ACS, SciELO, Springer, among others.

RESULTS

As per the literature, seventy-five natural flavones were predicted as active compounds with reference to their IC50 (<20 µg/mL) in in vitro studies. Also, synthetic flavones were found active against several diseases.

CONCLUSION

As per the literature, flavones are important sources for the potential treatment of multifactorial diseases. However, efforts toward the development of flavone-based therapeutic agents are still needed. The appearance of new catalysts and chemical transformations is expected to provide avenues for the synthesis of unexplored flavones, leading to the discovery of flavones with new properties and biological activities.

Inhibitory Effects of Quercetin and Its Main Methyl, Sulfate, and Glucuronic Acid Conjugates on Cytochrome P450 Enzymes, and on OATP, BCRP and MRP2 Transporters

Quercetin is a flavonoid, its glycosides and aglycone are found in significant amounts in several plants and dietary supplements. Because of the high presystemic biotransformation of quercetin, mainly its conjugates appear in circulation. As has been reported in previous studies, quercetin can interact with several proteins of pharmacokinetic importance. However, the interactions of its metabolites with biotransformation enzymes and drug transporters have barely been examined. In this study, the inhibitory effects of quercetin and its most relevant methyl, sulfate, and glucuronide metabolites were tested on cytochrome P450 (CYP) (2C19, 3A4, and 2D6) enzymes as well as on organic anion-transporting polypeptides (OATPs) (OATP1A2, OATP1B1, OATP1B3, and OATP2B1) and ATP (adenosine triphosphate) Binding Cassette (ABC) (BCRP and MRP2) transporters. Quercetin and its metabolites (quercetin-3'-sulfate, quercetin-3-glucuronide, isorhamnetin, and isorhamnetin-3-glucuronide) showed weak inhibitory effects on CYP2C19 and 3A4, while they did not affect CYP2D6 activity. Some of the flavonoids caused weak inhibition of OATP1A2 and MRP2. However, most of the compounds tested proved to be strong inhibitors of OATP1B1, OATP1B3, OATP2B1, and BCRP. Our data demonstrate that not only quercetin but some of its conjugates, can also interact with CYP enzymes and drug transporters. Therefore, high intake of quercetin may interfere with the pharmacokinetics of drugs.

Kaempferol modulates TCDD- and t-BHQ-induced drug-metabolizing enzymes and luteolin enhances this effect

The expression of drug-metabolizing enzymes is deeply involved in chemical-induced cancer progression and prevention. The aryl hydrocarbon receptor (AhR) induces phase I, and certain phase II drug-metabolizing enzymes after the binding of ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We have previously demonstrated that luteolin inhibited TCDD-induced AhR transformation, and modulated the expression of drug-metabolizing enzymes through not only the AhR, but also the nuclear factor-erythroid-2-related factor 2 (Nrf2). We have examined the effect of kaempferol on the expression of drug-metabolizing enzymes through modulation of the AhR- and Nrf2-pathways, and the effect of co-treatment with kaempferol and luteolin. Kaempferol dose-dependently inhibited not only the TCDD-induced expression of phase I and phase II drug-metabolizing enzymes, but also the tertiary butylhydroquinone (t-BHQ)-induced expression of phase II drug-metabolizing enzymes, by modulating the AhR- and Nrf2-pathways. Co-treatment with kaempferol and luteolin enhanced the inhibitory effect on the expression of drug-metabolizing enzymes, compared with either kaempferol or luteolin alone. Moreover, co-treatment with kaempferol and luteolin increased the cellular levels of kaempferol without affecting the levels of luteolin. An in vivo study was also performed and the results demonstrated that co-treatment with kaempferol and luteolin enhanced the inhibition of benzo[a]pyrene-induced drug-metabolizing enzymes compared with either kaempferol or luteolin alone, in the liver of ICR mice. These results suggest that luteolin promoted the incorporation of kaempferol into hepatocytes and enhanced the inhibitory effect of kaempferol on chemical-induced drug-metabolizing enzymes. Thus, luteolin enhances the kaempferol-inhibited expression of drug-metabolizing enzymes.

Strong and Selective Inhibitory Effects of the Biflavonoid Selamariscina A against CYP2C8 and CYP2C9 Enzyme Activities in Human Liver Microsomes

Like flavonoids, biflavonoids, dimeric flavonoids, and polyphenolic plant secondary metabolites have antioxidant, antibacterial, antiviral, anti-inflammatory, and anti-cancer properties. However, there is limited data on their effects on cytochrome P450 (P450) and uridine 5'-diphosphoglucuronosyl transferase (UGT) enzyme activities. In this study we evaluate the inhibitory potential of five biflavonoids against nine P450 activities (P450s1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A) in human liver microsomes (HLMs) using cocktail incubation and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The most strongly inhibited P450 activity was CYP2C8-mediated amodiaquine N-dealkylation with IC50 ranges of 0.019~0.123 μM. In addition, the biflavonoids-selamariscina A, amentoflavone, robustaflavone, cupressuflavone, and taiwaniaflavone-noncompetitively inhibited CYP2C8 activity with respective K_i values of 0.018, 0.083, 0.084, 0.103, and 0.142 μM. As selamariscina A showed the strongest effects, we then evaluated it against six UGT isoforms, where it showed weaker inhibition (UGTs1A1, 1A3, 1A4, 1A6, 1A9, and 2B7, IC50 1.7 μM). Returning to the P450 activities, selamariscina A inhibited CYP2C9-mediated diclofenac hydroxylation and tolbutamide hydroxylation with respective K_i values of 0.032 and 0.065 μM in a competitive and noncompetitive manner. However, it only weakly inhibited CYP1A2, CYP2B6, and CYP3A with respective K_i values of 3.1, 7.9, and 4.5 μM. We conclude that selamariscina A has selective and strong inhibitory effects on the CYP2C8 and CYP2C9 isoforms. This information might be useful in predicting herb-drug interaction potential between biflavonoids and co-administered drugs mainly metabolized by CYP2C8 and CYP2C9. In addition, selamariscina A might be used as a strong CYP2C8 and CYP2C9 inhibitor in P450 reaction-phenotyping studies to identify drug-metabolizing enzymes responsible for the metabolism of new chemicals.

Hepatoprotective effect of essential oils of Nepeta cataria L. on acetaminophen-induced liver dysfunction

Nepeta cataria L. has long been used in folk food and medicine for several functions. Essential oils (EOs) were extracted from Nepeta cataria L. by supercritical fluid extraction. The results of animal experiments showed that EOs from Nepeta cataria L. significantly attenuated acetaminophen-induced liver damage. Further study confirmed that EOs were able to increase mRNA expression of uridine diphosphate glucuronosyltransferases (UGTs) and sulfotransferases (SULTs), as well as inhibit CYP2E1 activities, and thereby suppressed toxic intermediate formation. Nrf-2 activation might be involved in EOs-induced up-regulation of Phase II enzymes. Collectively, our data provide evidence that EOs protect the liver against acetaminophen-induced liver injury mainly by accelerating acetaminophen harmless metabolism, implying that EOs can be considered as a potential natural resource to develop hepatoprotective agent.

The Essential Oils and Eucalyptol From Artemisia vulgaris L. Prevent Acetaminophen-Induced Liver Injury by Activating Nrf2-Keap1 and Enhancing APAP Clearance Through Non-Toxic Metabolic Pathway

Artemisia has long been used in traditional medicine and as a food source for different functions in eastern Asia. Artemisia vulgaris L. (AV) is a species of the genus Artemisia. Essential oils (EOs) were extracted from AV by subcritical butane extraction. EO contents were detected by electronic nose and headspace solid-phase microextraction coupled with gas chromatography (HS-SPME-GC-MS). To investigate the hepatoprotective effects, mice subjected to liver injury were treated intragastrically with EOs or eucalyptol for 3 days. Acetaminophen (APAP) alone caused severe liver injury characterized by significantly increased serum AST and ALT levels, ROS and hepatic malondialdehyde (MDA), as well as liver superoxide dismutase (SOD) and catalase (CAT) depletions. EOs significantly attenuated APAP-induced liver damages. Further study confirmed that eucalyptol is an inhibitor of Keap1, the affinity K D of eucalyptol and Keap1 was 1.42 × 10-5, which increased the Nrf2 translocation from the cytoplasm into the mitochondria. The activated Nrf2 increased the mRNA expression of uridine diphosphate glucuronosyltransferases (UGTs) and sulfotransferases (SULTs), also inhibiting CYP2E1 activities. Thus, the activated Nrf2 suppressed toxic intermediate formation, promoting APAP hepatic non-toxicity, whereby APAP was metabolized into APAP-gluc and APAP-sulf. Collectively, APAP non-toxic metabolism was accelerated by eucalyptol in protecting the liver against APAP-induced injury, indicating eucalyptol or EOs from AV potentials as a natural source of hepatoprotective agent.

Safety investigation of Pulsatilla chinensis saponins from chronic metabonomic study of serum biomedical changes in oral treated rat

ETHNOPHARMACOLOGICAL RELEVANCE

Pulsatilla chinensis (Bunge) Regel is a valuable traditional Chinese medicine (TCM) which is widely used for the treatment of schistosomiasis, inflammatory, bacterial infections. In recent years, P chinensis has been reported to exhibit antitumor activities. However, the mechanisms underlying its toxic effects remain largely unresolved. This paper is designed to investigate the damage of long-term oral P. chinensis saponins (PRS) and to explore its potential damage mechanisms by serum metabonomics approach.

MATERIALS AND METHODS

The serum samples from control and PRS treated rats were analyzed by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) in positive ionization mode and negative ionization mode. Liver function index of ALT, AST and ALP, blood biochemistry and biomarkers were examined to identify specific changes of injury. Acquired data were subjected to principal component analysis (PCA) for differentiating the control and PRS treated groups. Then, serum metabolic profiling was analyzed and pathway analysis performed on the biomarkers reversed after PRS treated and further integration of metabolic networks.

RESULTS

The results suggested that serum liver function indexes of ALT had significantly changed and stage increased. AST, ALP detection content show volatility changes. Changes in the 15 biomarkers found in the serum, such as acetaminophen glucuronide, 9 E, 11 E-linoleic acid, chenodeoxycholic acid, monoacylglycerides, sphingomyelin (SM), 7-ketodeoxycholic acid and 12-keto-deoxycholic acid, which were closely related to changes in liver injury. It could be seen clearly that with the change of the dosing time, the biomarkers in the serum have undergone obvious, regular and progressive changes through the score plot and corresponding loading plot. The underlying regulations of PRS-perturbed metabolic pathways were discussed according to the identified metabolites.

CONCLUSION

The present study proves the potential of UPLC-QTOF-MS based metabonomics in mapping metabolic response. Long-term oral administration of P. chinensis saponins can cause chronic liver injury, and its safety needs further attention. It is of great significance in safeguarding human health to explore the damage mechanism of Pulsatilla chinensis saponins on liver by serum metabolomics.

Resveratrol glucuronidation in vitro: potential implications of inhibition by probenecid

OBJECTIVES

Resveratrol is a naturally occurring antioxidant with therapeutic potential in prevention and treatment of neoplastic disease and other human disorders. However, net clearance of resveratrol in humans is very high, mainly due to glucuronide conjugation. This leads to extensive presystemic extraction and low plasma concentrations after oral dosage. The present study evaluated the effect of probenecid, an inhibitor of glucuronide conjugation, on resveratrol metabolism in vitro.

METHODS

Biotransformation of resveratrol to its 3-O-glucuronide and 4'-O-glucuronide conjugates was studied in vitro using human liver microsomal preparations. The mechanism and inhibitory potency of probenecid were evaluated based on a mixed competitive-noncompetitive inhibition model.

KEY FINDINGS

Probenecid inhibition of resveratrol 3-O-glucuronidation was predominantly noncompetitive, with an inhibition constant (K_i ) averaging 3.1 mm.

CONCLUSIONS

The ratio of in vivo maximum concentration of probenecid [I] during usual clinical use to the in vitro K_i value ([I]/K_i ) exceeds the boundary value of 0.1, used by regulatory agencies to identify the possibility of clinical drug interactions. This finding, together with the known property of probenecid as an inhibitor of glucuronide conjugation in humans, suggests that probenecid could serve as a pharmacokinetic boosting agent to enhance systemic exposure to resveratrol in humans.

Luteolin-Mediated Inhibition of Hepatic Stellate Cell Activation via Suppression of the STAT3 Pathway

Hepatic stellate cell (HSC) activation is responsible for hepatic fibrogenesis and is associated with an overexpression of transcription 3 (STAT3). Luteolin, a common dietary flavonoid with potent anti-inflammatory properties, has previously demonstrated antifibrogenic properties in HSCs but the mechanism has not been fully elucidated. Activated human and rat hepatic stellate cell lines LX-2 and HSC-T6 were used to study the effects of luteolin on HSCs. Cellular proteins were determined by western blot and immunofluorescence. Cell proliferation was assessed with Alamar Blue assay. Luteolin significantly decreased LX-2 and HSC-T6 cell viability in a time-and-dose-dependent manner, as well as decreased HSC end-products α-smooth muscle actin (α-SMA), collagen I, and fibronectin. Luteolin decreased levels of total and phosphorylated STAT3, suppressed STAT3 nuclear translocation and transcriptional activity, and attenuated expression of STAT3-regulated proteins c-myc and cyclin D1. STAT3 specific inhibitors stattic and SH-4-54 demonstrated similar effects on HSC viability and α-SMA production. In LX-2 and HSC-T6 cells, luteolin demonstrates a potent ability to inhibit hepatic fibrogenesis via suppression of the STAT3 pathway. These results further elucidate the mechanism of luteolin as well as the effect of the STAT3 pathway on HSC activation.

Mechanism of in-vitro inhibition of UGT1A1 by paritaprevir

OBJECTIVES

The direct-acting protease inhibitor paritaprevir is a new pharmaco-logic option available for treatment of chronic hepatitis C (HCV). Paritaprevir is reported to inhibit human UGT 1A1, but the mechanism of inhibition and its possible clinical consequences are not established. Our objective was to evaluate the in-vitro metabolic interaction between paritaprevir and the oral contraceptive steroid ethinyl estradiol (EE), a UGT 1A1 substrate.

METHODS

Enzyme kinetic parameters were determined using human liver microsomes for the biotransformation of EE to its glucuronide metabolites, and the potency and mechanism of inhibition by paritaprevir. Probenecid was used as a reference inhibitor for purposes of assay validation.

KEY FINDINGS

The underlying pattern of EE kinetics was complex, with evidence of substrate inhibition. The in-vitro inhibition constant (K_i ) value for paritaprevir vs EE on average was 20 μm and was consistent with a competitive inhibition mechanism. The ratio of in-vivo maximum plasma concentration of paritaprevir to in-vitro K_i was <0.1.

CONCLUSIONS

Paritaprevir is an in-vitro inhibitor of UGT 1A1. However, the in-vitro K_i value relative to maximum clinical plasma concentrations is below the threshold to trigger a recommendation for pharmacokinetic drug interaction studies.