Effects of myricetin, an antioxidant, on the pharmacokinetics of losartan and its active metabolite, EXP-3174, in rats: possible role of cytochrome P450 3A4, cytochrome P450 2C9 and P-glycoprotein inhibition by myricetin

Evaluation of pharmacokinetic herb-drug interaction of diabecon and losartan by UHPLC-MS/MS

The diabecon is an ayurvedic herbal formulation that contains a mixture of herbs traditionally used as antidiabetic which is reported in the ayurvedic pharmacopeia of India and Indian Materia medica. The diabetic population has a common co-morbidity of hypertension for which losartan drug is commonly used for the treatment of hypertension. However, there is a lack of research on the pharmacokinetics interaction between diabecon and losartan. This research aims to investigate the influence of diabecon on the pharmacokinetics of losartan drugs in rats by establishing a highly sensitive ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometry (UHPLC-MS/MS) method. The method was validated according to the USFDA guidelines and was applied for the pharmacokinetic study. The lowest concentration of losartan detection in rat plasma was found to be 1 ng/mL and the accuracy and precision were within the linear range (1-1500 ng/mL). The results revealed that after 28 days of dosing diabecon, it has altered the pharmacokinetic parameters like area under the curve (AUC0-t), drug clearance (Cl/F), and rate of elimination (Ke) of losartan, which may happen due to enzyme induction. Although there was a change in the pharmacokinetic parameters of losartan when administered in the presence of diabecon, it was found to be nonsignificant in rats (p > 0.05). According to the best of our knowledge, this is the first article that discusses the pharmacokinetic herb-drug interaction between diabecon and losartan.

Effects of bergapten on the pharmacokinetics of macitentan in rats both in vitro and in vivo

Macitentan was approved by the United States Food and Drug Administration (FDA) in 2013 for the treatment of pulmonary arterial hypertension (PAH). Bergapten is a furanocoumarin that is abundant in Umbelliferae and Rutaceae plants and is widely used in many Chinese medicine prescriptions. Considering the possible combination of these two compounds, this study is aimed to investigate the effects of bergapten on the pharmacokinetics of macitentan both in vitro and in vivo. Rat liver microsomes (RLMs), human liver microsomes (HLMs), and recombinant human CYP3A4 (rCYP3A4) were used to investigate the inhibitory effects and mechanisms of bergapten on macitentan in vitro. In addition, pharmacokinetic parameters were also studied in vivo. Rats were randomly divided into two groups (six rats per group), with or without bergapten (10 mg/kg), and pretreated for 7 days. An oral dose of 20 mg/kg macitentan was administered to each group 30 min after bergapten or 0.5% CMC-Na administration on day 7. Blood was collected from the tail veins, and the plasma concentrations of macitentan and its metabolites were assessed by ultra-performance liquid chromatography - tandem mass spectrometer (UPLC-MS/MS). Finally, we analyzed the binding force of the enzyme and two small ligands by in silico molecular docking to verify the inhibitory effects of bergapten on macitentan. The in vitro results revealed that the IC₅₀ values for RLMs, HLMs, and rCYP3A4 were 3.84, 17.82 and 12.81 μM, respectively. In vivo pharmacokinetic experiments showed that the AUC_(0-t), AUC_(0-∞), and C_max of macitentan in the experimental group (20,263.67 μg/L*h, 20,378.31 μg/L*h and 2,999.69 μg/L, respectively) increased significantly compared with the control group (7,873.97 μg/L*h, 7,897.83 μg/L*h and 1,339.44 μg/L, respectively), while the CL_z/F (1.07 L/h/kg) of macitentan and the metabolite-parent ratio (MR) displayed a significant decrease. Bergapten competitively inhibited macitentan metabolism in vitro and altered its pharmacokinetic characteristics in vivo. Further molecular docking analysis was also consistent with the experimental results. This study provides a reference for the combined use of bergapten and macitentan in clinical practice.

Myricetin: A Significant Emphasis on Its Anticancer Potential via the Modulation of Inflammation and Signal Transduction Pathways

Cancer is a major public health concern worldwide and main burden of the healthcare system. Regrettably, most of the currently used cancer treatment approaches such as targeted therapy, chemotherapy, radiotherapy and surgery usually cause adverse complications including hair loss, bone density loss, vomiting, anemia and other complications. However, to overcome these limitations, there is an urgent need to search for the alternative anticancer drugs with better efficacy as well as less adverse complications. Based on the scientific evidences, it is proven that naturally occurring antioxidants present in medicinal plants or their bioactive compounds might constitute a good therapeutic approach in diseases management including cancer. In this regard, myricetin, a polyhydroxy flavonol found in a several types of plants and its role in diseases management as anti-oxidant, anti-inflammatory and hepato-protective has been documented. Moreover, its role in cancer prevention has been noticed through modulation of angiogenesis, inflammation, cell cycle arrest and induction of apoptosis. Furthermore, myricetin plays a significant role in cancer prevention through the inhibition of inflammatory markers such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (Cox-2). Moreover, myricetin increases the chemotherapeutic potential of other anticancer drugs through modulation of cell signaling molecules activity. This review elaborates the information of myricetin role in cancer management through modulating of various cell-signaling molecules based on in vivo and in vitro studies. In addition, synergistic effect with currently used anticancer drugs and approaches to improve bioavailability are described. The evidences collected in this review will help different researchers to comprehend the information about its safety aspects, effective dose for different cancers and implication in clinical trials. Moreover, different challenges need to be focused on engineering different nanoformulations of myricetin to overcome the poor bioavailability, loading capacity, targeted delivery and premature release of this compound. Furthermore, some more derivatives of myricetin need to be synthesized to check their anticancer potential.

Phytochemicals That Interfere With Drug Metabolism and Transport, Modifying Plasma Concentration in Humans and Animals

Phytochemicals (Pch) present in fruits, vegetables and other foods, are known to inhibit or induce drug metabolism and transport. An exhaustive search was performed in five databases covering from 2000 to 2021. Twenty-one compounds from plants were found to modulate CYP3A and/or P-gp activities and modified the pharmacokinetics and the therapeutic effect of 27 different drugs. Flavonols, flavanones, flavones, stilbenes, diferuloylmethanes, tannins, protoalkaloids, flavans, hyperforin and terpenes, reduce plasma concentration of cyclosporine, simvastatin, celiprolol, midazolam, saquinavir, buspirone, everolimus, nadolol, tamoxifen, alprazolam, verapamil, quazepam, digoxin, fexofenadine, theophylline, indinavir, clopidogrel. Anthocyanins, flavonols, flavones, flavanones, flavonoid glycosides, stilbenes, diferuloylmethanes, catechin, hyperforin, alkaloids, terpenes, tannins and protoalkaloids increase of plasma concentration of buspirone, losartan, diltiazem, felodipine, midazolam, cyclosporine, triazolam, verapamil, carbamazepine, diltiazem, aripiprazole, tamoxifen, doxorubicin, paclitaxel, nicardipine. Interactions between Pchs and drugs affect the gene expression and enzymatic activity of CYP3A and P-gp transporter, which has an impact on their bioavailability; such that co-administration of drugs with food, beverages and food supplements can cause a subtherapeutic effect or overdose. Therefore, it is important for the clinician to consider these interactions to obtain a better therapeutic effect.

Formulation and Pharmacokinetic Evaluation of Ethyl Cellulose/HPMC-Based Oral Expandable Sustained Release Dosage of Losartan Potassium

Prolonged retention of losartan potassium in the upper gastrointestinal tract is anticipated to increase its absorption and exposure to CYP450 enzyme subfamilies, undertaking its conversion to more potent (10-40 times) active metabolite, losartan carboxylic acid (LCA). Consistent with this, hydroxypropyl methylcellulose K4M/ethyl cellulose-based novel expandable films (EFs) containing losartan potassium (LP) suitable for prolonged retention in the stomach were developed. The films were prepared by solvent casting method. USP type II dissolution apparatus (0.1 N HCl, 37°C, 100 rpm) was used to perform the dissolution testing (drug release, unfolding behavior, film integrity, erosion, and water uptake) of the films. In vivo pharmacokinetic studies were carried out in rabbits. An HPLC-UV method was used for the quantification of the drug and its active metabolite in plasma. These folded films placed inside hard gelatin capsule shells unfolded to full dimensions in dissolution medium and provided sustained drug release throughout 12 h. The plasma drug concentration-time curves obtained from the in vivo studies were used to determine pharmacokinetic parameters, such as area under the plasma drug concentration-time curve (AUC), area under first moment curve (AUMC), mean residence time (MRT), C_max, T_max, t_1/2, k_e, and F_r in comparison with that of the market formulation, Cozaar^®. The novel EFs significantly changed the pharmacokinetic parameters of the drug and its active metabolite. The apparent elimination rate constant (k_e) significantly decreased, while MRT and elimination half-life (t_1/2) increased in both cases. The relative bioavailabilities (F_r) of both LP and E3174 using the novel formulation were higher than that of Cozaar^®.

Effect of Myricetin on CYP2C8 Inhibition to Assess the Likelihood of Drug Interaction Using In Silico, In Vitro, and In Vivo Approaches

Myricetin, a bioflavonoid, is widely used as functional food/complementary medicine and has promising multifaceted pharmacological actions against therapeutically validated anticancer targets. On the other hand, CYP2C8 is not only crucial for alteration in the pharmacokinetics of drugs to cause drug interaction but also unequivocally important for the metabolism of endogenous substances like the formation of epoxyeicosatrienoic acids (EETs), which are considered as signaling molecules against hallmarks of cancer. However, there is hardly any information known to date about the effect of myricetin on CYP2C8 inhibition and, subsequently, the CYP2C8-mediated drug interaction potential of myricetin at the preclinical/clinical level. We aimed here to explore the CYP2C8 inhibitory potential of myricetin using in silico, in vitro, and in vivo investigations. In the in vitro study, myricetin showed a substantial effect on CYP2C8 inhibition in human liver microsomes using CYP2C8-catalyzed amodiaquine-N-deethylation as an index reaction. Considering the Lineweaver-Burk plot, the Dixon plot, and the higher α-value, myricetin is found to be a mixed type of CYP2C8 inhibitor. Moreover, in vitro-in vivo extrapolation data suggest that myricetin is likely to cause drug interaction at the hepatic level. The molecular docking study depicted a strong interaction between myricetin and the active site of the human CYP2C8 enzyme. Moreover, myricetin caused considerable elevation in the oral exposure of amodiaquine as a CYP2C8 substrate via a slowdown of amodiaquine clearance in the rat model. Overall, the potent action of myricetin on CYP2C8 inhibition indicates that there is a need for further exploration to avoid drug interaction-mediated precipitation of obvious adverse effects as well as to optimize anticancer therapy.

A randomized, double-blind, placebo-controlled, single, and multiple dose-escalation Phase I clinical trial to investigate the safety, pharmacokinetic, and pharmacodynamic profiles of oral S086, a novel angiotensin receptor-neprilysin inhibitor, in healthy Chinese volunteers

BACKGROUND

This study evaluated the safety, pharmacokinetic (PK), and pharmacodynamic (PD) profiles of single ascending doses (SAD) and multiple ascending doses (MAD) of S086 in healthy Chinese volunteers.

RESEARCH DESIGN AND METHODS

This randomized, double-blind, placebo-controlled, Phase I clinical trial enrolled 113 subjects, including 65 subjects in the SAD (60-1080 mg) study and 48 subjects in the MAD study (180-720 mg). The safety, PK (sacubitril, LBQ657, and EXP3174) and PD (MAD study: blood pressure, pulse) of S086 were assessed.

RESULTS

There were no deaths, serious adverse events, or discontinuations due to TEAEs, and there were no significant safety concerns associated with S086. PK parameters for sacubitril, LBQ657, and EXP3174 increased in a dose-dependent manner after single oral doses of S086. Plasma concentrations of sacubitril, LBQ657, and EXP3174 were maintained at steady state within 5 days of once-daily oral administration of S086. In the MAD study, S086 administration was associated with a dose-dependent decrease in mean diastolic and systolic blood pressure compared to baseline.

CONCLUSIONS

The safety and PK profile profiles of S086 support the use of S086 240 mg once daily in a future Phase II study in patients with heart failure.

TRIAL REGISTRATION

The trial is registered at chinadrugtrials.org.cn (CT.gov identifier: CTR20182350 and CTR20182351).

Myricetin: A comprehensive review on its biological potentials

Myricetin is a critical nutritive component of diet providing immunological protection and beneficial for maintaining good health. It is found in fruits, vegetables, tea, and wine. The families Myricaceae, Polygonaceae, Primulaceae, Pinaceae, and Anacardiaceae are the richest sources of myricetin. Different researchers explored the therapeutic potential of this valuable constituent such as anticancer, antidiabetic, antiobesity, cardiovascular protection, osteoporosis protection, anti-inflammatory, and hepatoprotective. In addition to these, the compound has been tested for cancer and diabetic mellitus during clinical trials. Health benefits of myricetin are related to its impact on different cell processes, such as apoptosis, glycolysis, cell cycle, energy balance, lipid level, serum protein concentrations, and osteoclastogenesis. This review explored the potential health benefits of myricetin with a specific emphasis on its mechanism of action, considering the most updated and novel findings in the field.

Pharmacokinetics of a Fixed-Dose Combination of Amlodipine/Losartan and Chlorthalidone Compared to Concurrent Administration of the Separate Components

Hypertension is more effectively treated with coadministration of 2 or more antihypertensive drugs than with high-dose monotherapy. Therefore, calcium channel blockers, angiotensin II receptor blockers, and thiazides are coadministered to treat hypertension. The objective of this study was to compare the pharmacokinetic (PK) profiles of HCP1401, a fixed-dose combination of amlodipine 5 mg, losartan 100 mg, and chlorthalidone 25 mg, with the separate components (loose combination) of amlodipine/losartan 5/100 mg and chlorthalidone 25 mg. A randomized, open-label, single-dose, 2-way crossover study was conducted. Blood samples for amlodipine and chlorthalidone were collected for up to 144 hours after dosing, whereas those for losartan were collected up to 48 hours after dosing. The PK parameters of these drugs were calculated using a noncompartmental method. Sixty subjects completed the study. The geometric mean ratios and 90% confidence intervals of maximum plasma concentration and area under the concentration-time curve to the last measurable point for amlodipine, losartan, and chlorthalidone were within the conventional bioequivalence range of 0.80 to 1.25. There were no clinically significant changes in safety assessments, and the treatments were well tolerated. The PK characteristics and tolerability profiles of a single oral FDC of amlodipine, losartan, and chlorthalidone were equivalent to those of individual tablets in a loose combination.

Enhancement of glioblastoma multiforme therapy through a novel Quercetin-Losartan hybrid

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor. Maximal surgical resection followed by radiotherapy and concomitant chemotherapy with temozolomide remains the first-line therapy, prolonging the survival of patients by an average of only 2.5 months. There is therefore an urgent need for novel therapeutic strategies to improve clinical outcomes. Reactive oxygen species (ROS) are an important contributor to GBM development. Here, we describe the rational design and synthesis of a stable hybrid molecule tethering two ROS regulating moieties, with the aim of constructing a chemopreventive and anticancer chemical entity that retains the properties of the parent compounds. We utilized the selective AT₁R antagonist losartan, leading to the inhibition of ROS levels, and the antioxidant flavonoid quercetin. In GBM cells, we show that this hybrid retains the binding potential of losartan to the AT₁R through competition-binding experiments and simultaneously exhibits ROS inhibition and antioxidant capacity similar to native quercetin. In addition, we demonstrate that the hybrid is able to alter the cell cycle distribution of GBM cells, leading to cell cycle arrest and to the induction of cytotoxic effects. Last, the hybrid significantly and selectively reduces cancer cell proliferation and angiogenesis in primary GBM cultures with respect to the isolated parent components or their simple combination, further emphasizing the potential utility of the current hybridization approach in GBM.

Effects of Xuesaitong on the Pharmacokinetics of Losartan: An In Vivo UPLC-MS/MS Study

The aim of this study was to examine whether Xuesaitong, a multiherbal formulation for coronary heart disease, alters the pharmacokinetics of losartan. Adult male Sprague Dawley rats randomly received losartan (10 mg/kg) or losartan plus Xuesaitong (10 mg/kg) through an oral gavage (n = 6). Multiple blood samples were obtained for up to 36 h to determine the concentrations of losartan and its active metabolite, EXP3174, through ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Pharmacokinetics were estimated using a noncompartmental model. The half-life (t_1/2) of losartan was decreased by Xuesaitong (4.26 ± 1.51 vs. 6.35 ± 2.10 h; P < 0.05). The apparent volume of distribution (V_d) of losartan was also decreased by the combination of losartan and Xuesaitong (4.41 ± 1.61 vs. 7.20 ± 2.41 mL; P < 0.05). The time to maximum concentration (T_max) of losartan was increased by Xuesaitong (1.06 ± 1.04 vs. 0.13 ± 0.05 h; P < 0.05). Xuesaitong also decreased the t_1/2 of EXP3174 (8.22 ± 1.41 vs. 6.29 ± 1.38 h; P < 0.05). These results suggest that there is a complex interaction between losartan and Xuesaitong. In addition to enhanced elimination of losartan and EXP3174, Xuesaitong may also decrease the absorption rate and V_d of losartan.

Interaction of soy isoflavones and their main metabolites with hOATP2B1 transporter

Membrane organic anion-transporting polypeptides (OATPs) are responsible for the drug transmembrane transport within the human body. The function of OATP2B1 transporter can be inhibited by various natural compounds. Despite increased research interest in soya as a part of human diet, the effect of its active components to interact with hOATP2B1 has not been elucidated in a complex extent. This in vitro study examined the inhibitory effect of main soy isoflavones (daidzin, daidzein, genistin, genistein, glycitin, glycitein, biochanin A, formononetin) and their metabolites formed in vivo (S-equol, O-desmethylangolensin) towards human OATP2B1 transporter. MDCKII cells overexpressing hOATP2B1 were employed to determine quantitative inhibitory parameters of the tested compounds and to analyze mechanism/s of the inhibitory interaction. The study showed that aglycones of soy isoflavones and the main biologically active metabolite S-equol were able to significantly inhibit hOATP2B1-mediated transport. The Ki values for most of aglycones range from 1 to 20 μM. In contrast, glucosides did not exhibit significant inhibitory effect. The kinetic analysis did not indicate a uniform type of inhibition towards the hOATP2B1 although predominant mechanism of inhibition seemed to be competitive. These findings may suggest that tested soy isoflavones and their metabolites might affect transport of xenobiotics including drugs across tissue barriers via hOATP2B1.

Electronic states of Myricetin. UV-Vis polarization spectroscopy and quantum chemical calculations

Myricetin (3,3',4',5,5',7'-hexahydroxyflavone) was investigated by linear dichroism spectroscopy on molecular samples partially aligned in stretched poly(vinyl alcohol) (PVA). At least five electronic transitions in the range 40,000-20,000cm^-1 were characterized with respect to their wavenumbers, relative intensities, and transition moment directions. The observed bands were assigned to electronic transitions predicted with TD-B3LYP/6-31+G(d,p).

An update on the role of intestinal cytochrome P450 enzymes in drug disposition

Oral administration is the most commonly used route for drug treatment. Intestinal cytochrome P450 (CYP)-mediated metabolism can eliminate a large proportion of some orally administered drugs before they reach systemic circulation, while leaving the passage of other drugs unimpeded. A better understanding of the ability of intestinal P450 enzymes to metabolize various clinical drugs in both humans and preclinical animal species, including the identification of the CYP enzymes expressed, their regulation, and the relative importance of intestinal metabolism compared to hepatic metabolism, is important for improving bioavailability of current drugs and new drugs in development. Here, we briefly review the expression of drug-metabolizing P450 enzymes in the small intestine of humans and several preclinical animal species, and provide an update of the various factors or events that regulate intestinal P450 expression, including a cross talk between the liver and the intestine. We further compare various clinical and preclinical approaches for assessing the impact of intestinal drug metabolism on bioavailability, and discuss the utility of the intestinal epithelium–specific NADPH-cytochrome P450 reductase-null (IECN) mouse as a useful model for studying in vivo roles of intestinal P450 in the disposition of orally administered drugs.

Negligible Pharmacokinetic Interaction of Red Ginseng and Losartan, an Antihypertensive Agent, in Sprague-Dawley Rats

Red ginseng (RG) is one of the top selling herbal medicines in Korea, but is not recommended in hypertensive patients. In this study, the pharmacokinetic (PK) interaction between RG and losartan, an antihypertensive drug, was examined. RG was orally administered for 2 wk to male Sprague-Dawley (S-D) rats at either control (0), 0.5, 1, or 2 g/kg/d for 2 wk. After the last administration of RG and 30 min later, all animals were treated with 10 mg/kg losartan by oral route. In addition, some S-D rats were administered RG orally for 21 d at 2 g/kg followed by losartan intravenously (iv) at 10 mg/kg/d. Post losartan administration, plasma samples were collected at 5, 15, and 30 min and 1, 1.5, 2, 3, 6, 12, and 24 h. Plasma concentrations of losartan and E-3174, the active metabolite of losartan, were analyzed by a high-pressure liquid chromatography-tandem mass spectrometer system (LC-MS/MS). Oral losartan administration showed dose-dependent pharmacokinetics (PK) increase with time to maximum plasma, but this was not significant between different groups. There was no significant change in tmax with E-3174 PK. With iv losartan, pharmacokinetics showed elevation of area under the plasma concentration-time curve from time zero extrapolated to infinitity. There was not a significant change in AUCinf with E-3174 PK. Therefore, RG appeared to interfere with biotransformation of losartan, as RG exerted no marked effect on E-3174 PK in S-D rats. Data demonstrated that oral or iv treatment with losartan in rats pretreated with RG for 2 wk showed that losartan PK was affected but E-3174 PK remained unchanged among different dose groups. These results suggested that RG induces negligible influence on losartan and E-3174 PK in rats.

Recent trends in preclinical drug-drug interaction studies of flavonoids--Review of case studies, issues and perspectives

Because of health benefits that are manifested across various disease areas, the consumption of herbal products and/or health supplements containing different kinds of flavonoids has been on the rise. While the drug-drug interaction potential between flavonoids and co-ingested drugs still remain an issue, opportunities exist for the combination of flavonoids with suitable anti-cancer drugs to enhance the bioavailability of anti-cancer drugs and thereby reduce the dose size of the anti-cancer drugs and improve its therapeutic index. In recent years, scores of flavonoids have undergone preclinical investigation with variety of drugs encompassing therapeutic areas such as oncology (etoposide, doxorubicin, paclitaxel, tamoxifen etc.), immunosuppression (cyclosporine) and hypertension (losartan, felodipine, nitrendipine etc.). The review provides examples of the recent trends in the preclinical investigation of 14 flavonoids (morin, quercetin, silibinin, kaempferol etc.) with various co-administered drugs. The relevance of combination of flavonoids with anti-cancer drugs and a framework to help design the in vitro and in vivo preclinical studies to gain better mechanistic insights are discussed. Also, concise discussions on the various physiological factors that contribute for the reduced bioavailability of flavonoids along with the significant challenges in the data interpretation are provided.

Phloridzin-sensitive transport of echinacoside and acteoside and altered intestinal absorption route after application of Cistanche tubulosa extract

Objectives

The objective of this study was to address the beneficial effects of Cistanche tubulosa extract on improving the low intestinal permeability of echinacoside (ECH) and acteoside (ACT).

Methods

Absorption of ECH and ACT in C. tubulosa extract was characterized using human intestinal Caco-2 cell monolayers with intact compounds. Glucose transporter-dependent absorption of ECH and ACT was confirmed by an in-situ intestinal perfusion technique.

Key findings

The apparent permeability (Papp) was not significantly different between intact ECH and intact ACT. In the presence of phloridzin, the Papp of the ECH and ACT at a high dose was reduced to 20% of the respective non-treatment, but was not altered by phloretin and verapamil. C. tubulosa extract at low and high doses enhanced the Papp of ECH and ACT (both by threefold), resulting in their large participation in sodium-dependent glucose transporter-independent absorption. At a low concentration, concomitant ECH and ACT levels in portal blood were significantly suppressed by phloridzin.

Conclusion

The dietary and medicinal C. tubulosa extract enhancing the intestinal absorption of ECH and ACT may serve to better manage human health, although the involvement of phloridzin-sensitive transport should be reduced.

Effects of licochalcone A on the bioavailability and pharmacokinetics of nifedipine in rats: possible role of intestinal CYP3A4 and P-gp inhibition by licochalcone A

The purpose of this study was to investigate the possible effects of licochalcone A (a herbal medicine) on the pharmacokinetics of nifedipine and its main metabolite, dehydronifedipine, in rats. The pharmacokinetic parameters of nifedipine and/or dehydronifedipine were determined after oral and intravenous administration of nifedipine to rats in the absence (control) and presence of licochalcone A (0.4, 2.0 and 10 mg/kg). The effect of licochalcone A on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity was also evaluated. Nifedipine was mainly metabolized by CYP3A4. Licochalcone A inhibited CYP3A4 enzyme activity in a concentration-dependent manner with a 50% inhibition concentration (IC50 ) of 5.9 μm. In addition, licochalcone A significantly enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp. The area under the plasma concentration-time curve from time 0 to infinity (AUC) and the peak plasma concentration (Cmax ) of oral nifedipine were significantly greater and higher, respectively, with licochalcone A. The metabolite (dehydronifedipine)-parent AUC ratio (MR) in the presence of licochalcone A was significantly smaller compared with the control group. The above data could be due to an inhibition of intestinal CYP3A4 and P-gp by licochalcone A. The AUCs of intravenous nifedipine were comparable without and with licochalcone A, suggesting that inhibition of hepatic CYP3A4 and P-gp was almost negligible.

In vivo and in vitro addition of dried olive extract in poultry

A freeze-dried powder from organic olive (Olea europaea) juice extract, contains 8.82% polyphenols and a minimum of 2.5% hydroxytyrosol (3,4-dihydroxyphenylethanol), an effective free radical scavenger and the major antioxidant in the byproduct (dried olive extract, DOE). Myricetin, a bioflavonoid extract from the bark powder of the bayberry tree (Myrica cerifera), also has many beneficial biological properties and antioxidative capacity. While well-known as antioxidants, the capacity of these compounds to retard lipid oxidation in foods containing unsaturated fatty acids has not been widely evaluated. Thus, a study was conducted to assess the capacity of DOE to (1) enhance the growth of poultry, (2) determine the effectiveness of DOE (administered in vivo) as an antioxidant in post-mortem tissue and further processed meat, and (3) compare the in vitro antioxidative capacity of hydroxytyrosol and myricetin. DOE was administered ad libitum in water at 6 and 12 mg per bird per day for 6 weeks in a factorial design: 3 diets (control plus two treatment levels) × 2 blocks × 2 replications. There was no enhancement of feed consumption, body weight (BW), or feed conversion by DOE; overall means for these measurements were 5.49 kg per bird, 3.32 kg per bird, and 1.65 g feed per g live BW, respectively. Diagnostic examinations of two birds per pen at the end of the study revealed no adverse effects due to consumption of DOE, a generally recognized as safe substance. The byproduct, administered in vivo, did not retard lipid oxidation in fresh, heated, or NaCl (1.0% w/w)/heated/stored meat as assessed by absorbance values for thiobarbituric acid reactive substances at 532 nm and 2,2-diphenylpicrylhydrazyl at 517 nm. Both the byproduct and hydroxytyrosol are highly water-soluble and may have been unavailable as an antioxidant in the tissue of broilers that did not consume water for 4-6 h prior to processing. As an additive in processed thigh meat, 6 and 12 mg of DOE (2.5% hydroxytyrosol) per 3 mg of meat, although not as effective as myricetin (95% purity), reduced oxidation. Further assessment revealed that hydroxytyrosol from the DOE, added at (1)/38 the concentration of myricetin, was almost 50% as effective.

Modulation of CYP2D6 and CYP3A4 metabolic activities by Ferula asafetida resin

Present study investigated the potential effects of Ferula asafetida resin on metabolic activities of human drug metabolizing enzymes: CYP2D6 and CYP3A4. Dextromethorphan (DEX) was used as a marker to assess metabolic activities of these enzymes, based on its CYP2D6 and CYP3A4 mediated metabolism to dextrorphan (DOR) and 3-methoxymorphinan (3-MM), respectively. In vitro study was conducted by incubating DEX with human liver microsomes and NADPH in the presence or absence of Asafetida alcoholic extract. For clinical study, healthy human volunteers received a single dose of DEX alone (phase-I) and repeated the same dose after a washout period and four-day Asafetida treatment (phase-II). Asafetida showed a concentration dependent inhibition on DOR formation (in vitro) and a 33% increase in DEX/DOR urinary metabolic ratio in clinical study. For CYP3A4, formation of 3-MM in microsomes was increased at low Asafetida concentrations (10, 25 and 50 μg/ml) but slightly inhibited at the concentration of 100 μg/ml. On the other hand, in vivo observations revealed that Asafetida significantly increased DEX/3-MM urinary metabolic ratio. The findings of this study suggest that Asafetida may have a significant effect on CYP3A4 metabolic activity. Therefore, using Ferula asafetida with CYP3A4 drug substrates should be cautioned especially those with narrow therapeutic index such as cyclosporine, tacrolimus and carbamazepine.

Effect of Garden Cress Seeds Powder and Its Alcoholic Extract on the Metabolic Activity of CYP2D6 and CYP3A4

The powder and alcoholic extract of dried seeds of garden cress were investigated for their effect on metabolic activity of CYP2D6 and CYP3A4 enzymes. In vitro and clinical studies were conducted on human liver microsomes and healthy human subjects, respectively. Dextromethorphan was used as a common marker for measuring metabolic activity of CYP2D6 and CYP3A4 enzymes. In in vitro studies, microsomes were incubated with NADPH in presence and absence of different concentrations of seeds extract. Clinical investigations were performed in two phases. In phase I, six healthy female volunteers were administered a single dose of dextromethorphan and in phase II volunteers were treated with seeds powder for seven days and dextromethorphan was administered with last dose. The O-demethylated and N-demethylated metabolites of dextromethorphan were measured as dextrorphan (DOR) and 3-methoxymorphinan (3-MM), respectively. Observations suggested that garden cress inhibits the formation of DOR and 3-MM metabolites. This inhibition of metabolite level was attributed to the inhibition of CYP2D6 and CYP3A4 activity. Garden cress decreases the level of DOR and 3-MM in urine and significantly increases the urinary metabolic ratio of DEX/DOR and DEX/3-MM. The findings suggested that garden cress seeds powder and ethanolic extract have the potential to interact with CYP2D6 and CYP3A4 substrates.

Influence of compound danshen tablet on the pharmacokinetics of losartan and its metabolite EXP3174 by liquid chromatography coupled with mass spectrometry

Losartan is an effective anti-hypotension drug frequently used in clinic. Compound danshen tablet (CDST) is an important traditional Chinese multiherbal formula composed of Danshen, Sanqi and Bingpian, which is widely used for the treatment of cardiovascular and cerebrovascular diseases in China. More often, losartan and CDST are simultaneously used for the treatment of anti-hypertension in the clinic. The aim of this study was to compare the pharmacokinetics of losartan and EXP3174 after oral administration of single losartan and both losartan and CDST, and to investigate the influence of CDST on the pharmacokinetics of losartan and its metabolite EXP3174. Male Sprague-Dawley rats were randomly assigned to two groups: a losartan-only group and a losartan and CDST group. Plasma concentrations of losartan and EXP3174 were determined by LC-MS at designated points after drug administration, and the main pharmacokinetic parameters were estimated. It was found that there were significant differences (p < 0.05) between the pharmacokinetic parameters of losartan and EXP3174, which showed that CDST influenced the metabolism and excretion of losartan in vivo. The result could be used for clinical medication guidance of losartan and CDST to avoid the occurrence of adverse reactions.

Pharmacokinetic interaction between losartan and Rhodiola rosea in rabbits

AIM

The study investigates the potential interaction of the herbal medicinal product of Rhodiola rosea on the pharmacokinetics of losartan and its active metabolite EXP3174 after concurrent oral administration to rabbits.

MATERIALS AND METHODS

We conducted a randomized, single-dose, two-treatment, two-period, two-sequence, cross-over pharmacokinetic study on 6 healthy female New Zealand rabbits, after concurrent oral administration of losartan (5 mg/kg) and the herbal medicinal product of R. rosea (50 mg/kg). Quantification of losartan and its main active metabolite EXP3174 was achieved using a validated HPCL/UV method. Pharmacokinetic and statistical analysis was performed using the EquivTest/PK software.

OBSERVATIONS

Administration of the herbal medicinal product of R. rosea resulted in a statistically significant increase of the following pharmacokinetic parameters for losartan: the maximum plasma concentration (C(max)), the area under the curve (AUC) and the apparent total body clearance (CL/F). An almost 2-fold increase in the AUC of losartan was observed after concurrent administration of the herbal medicinal product of R. rosea. No statistically significant alteration was observed in the pharmacokinetic parameters of the active metabolite of losartan EXP3174.

CONCLUSION

The data of this study suggest that R. rosea significantly alters the pharmacokinetic properties of losartan after concurrent oral administration to rabbits. A study in humans should be conducted to assess the clinical significance of a possible herb-drug interaction between the herbal medicinal products of R. rosea and drugs such as losartan, which are substrates of both CYPs and P-gp.

Inhibitory effects of cytochrome P450 enzymes CYP2C8, CYP2C9, CYP2C19 and CYP3A4 by Labisia pumila extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Labisa pumila (LP), popularly known with its local name, Kacip Fatimah, is a well known herb grown in Indochina and Southeast Asia and is traditionally used to regain energy after giving birth in women. The propensity of LP to cause drug-herb interaction via cytochrome P450 (CYP) enzyme system has not been investigated.

AIM OF THE STUDY

To evaluate the in vitro inhibitory effects of various LP extracts (aqueous, ethanol, dichloromethane (DCM) and hexane) on cytochrome P450 2C8 (CYP2C8), CYP2C9, CYP2C19 and CYP3A4 activities.

MATERIALS AND METHODS

Probe substrate-based high performance liquid chromatography (HPLC) methods were established for CYP2C9, CYP2C19 and CYP3A4 whereas a fluorescence-based enzyme assay was established for CYP2C8. The metabolite formations were examined after incubation of probe substrate with respective CYP isoform in the present or absent of LP extracts. The inhibitory effect of LP was characterized with kinetic parameters IC(50) and K(i) values.

RESULTS

LP extracts showed differential effect of CYP activities with the order of inhibitory potency as follows: dichloromethane>hexane>ethanol>aqueous. This differential effect was only observed in CYP2C isoforms but not CYP3A4. Both the hexane and DCM extracts exhibited moderate to potent inhibition towards CYP2C activities in different modes including non-competitive, competive and mixed-type. The DCM effect was notably strong for CYP2C8 and CYP2C9 showing K(i) values of below 1 μg/ml. The selectivity of LP for CYP2C isoforms rather than CYP3A4 may be attributed to the presence of relatively small, lipophilic yet slightly polar compounds within the LP extracts.

CONCLUSIONS

The results of our study revealed that phytoconstituents contained in LP, particularly in hexane and dichloromethane extracts, were able to selectively inhibit CYP2C isoforms. The inactivation was characterized by low K(i) values, in particular, in CYP2C8 and CYP2C9. These in vitro data indicate that LB preparations contain constituents that can potently inhibit CYP2C activities and suggest that this herb should be examined for potential pharmacokinetic drug interactions in vivo.

Effects of ticlopidine on pharmacokinetics of losartan and its main metabolite EXP-3174 in rats

AIM

Losartan and antiplatelet agent ticlopidine can be prescribed concomitantly for prevention or therapy of cardiovascular diseases. Hence, the effects of ticlopidine on the pharmacokinetics of losartan and its active metabolite EXP-3174 were evaluated in rats.

METHODS

Ticlopidine (4 or 10 mg/kg po) was administered 30 min before administration of losartan (9 mg/kg po or 3 mg/kg iv). The activity of human CYP2C9 and 3A4 were measured using the CYP inhibition assay kit. The activity of P-gp was evaluated using rhodamine-123 retention assay in MCF-7/ADR cells.

RESULTS

Ticlopidine (10 mg/kg) significantly increased the areas under the plasma concentration-time curves (AUCs) and peak plasma concentration (C(max)) of oral losartan (9 mg/kg), as well as the AUCs of the active metabolite EXP-3174. Ticlopidine (10 mg/kg) did not significantly change the pharmacokinetics of intravenous losartan (3 mg/kg). Ticlopidine inhibited CYP2C9 and 3A4 with IC₅₀ values of 26.0 and 32.3 μmol/L, respectively. The relative cellular uptake of rhodamine-123 was unchanged.

CONCLUSION

The significant increase in the AUC of losartan (9 mg/kg) by ticlopidine (10 mg/kg) could be attributed to the inhibition of CYP2C9- and 3A4-mediated losartan metabolism in small intestine and/or in liver. The inhibition of P-gp in small intestine and reduction of renal elimination of losartan by ticlopidine are unlikely to be causal factors.

Effects of myricetin, an anticancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its main metabolite, 4-hydroxytamoxifen, in rats

This study examined the effect of myricetin, an anticancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, in rats. The effect of myricetin on P-glycoprotein (P-gp), cytochrome P450 (CYP)3A4 and 2C9 activity was evaluated. Myricetin inhibited CYP3A4 and 2C9 activity with IC(50) values of 7.81 and 13.5 μM, respectively, and significantly inhibited P-gp activity in a concentration-dependent manner. Pharmacokinetic parameters of tamoxifen and 4-hydroxytamoxifen were determined in rats after oral (10 mg/kg) and intravenous (2 mg/kg) administration of tamoxifen in the presence and absence of myricetin (0.4, 2, and 8 mg/kg). Compared with the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve (AUC(0-∞)) and the peak plasma concentration (C (max)) of tamoxifen were significantly (P < 0.05, 2 mg/kg; P < 0.01, 8 mg/kg) increased by 41.8-74.4 and 48.4-81.7%, respectively. Consequently, the absolute bioavailability (AB) of tamoxifen with myricetin (2 and 8 mg/kg) was 29.0-35.7%, which was significantly enhanced (P < 0.05 for 2 mg/kg, P < 0.01 for 8 mg/kg) compared with the oral control group (20.4%). Moreover, the relative bioavailability (RB) of tamoxifen was 1.14- to 1.74-fold greater than that of the control group. The metabolite-parent AUC ratio (MR) was significantly reduced (P < 0.05, 8 mg/kg), implying that the formation of 4-hydroxytamoxifen was considerably affected by myricetin. The enhanced bioavailability of tamoxifen might be mainly due to inhibition of the CYP3A4- and CYP2C9-mediated metabolism of tamoxifen in the small intestine and/or in the liver, and inhibition of P-gp efflux pump in the small intestine by myricetin.