Herb-drug interactions: Focus on metabolic enzymes and transporters

Analysis of the chemical constituents and their metabolites in Orthosiphon stamineus Benth. via UHPLC-Q exactive orbitrap-HRMS and AFADESI-MSI techniques

BACKGROUND

Known for its strong diuretic properties, the perennial herbaceous plant Orthosiphon stamineus Benth. is believed to preserve the kidney disease. This study compared the boiling water extract with powdered Orthosiphon stamineus Benth. and used a highly sensitive and high resolution UHPLC-Q-Exactive-Orbitrap-HRMS technology to evaluate its chemical composition.

RESULTS

Furthermore, by monitoring the absorption of prototype components in rat plasma following oral treatment, the beneficial ingredients of the Orthosiphon stamineus Benth. decoction was discovered. Approximately 92 substances underwent a preliminary identification utilizing relevant databases, relevant literature, and reference standards. As the compound differences between the powdered Orthosiphon stamineus Benth. and its water decoction were analyzed, it was found that boiling produced additional compounds, 48 of which were new. 45 blood absorption prototype components and 49 OS metabolites were discovered from rat serum, and a kidney tissue homogenate revealed an additional 28 prototype components. Early differences in the distribution of ferulic acid, cis 4 coumaric acid, and rosmarinic acid were shown using spatial metabolomics. It was elucidated that the renal cortex region is where rosmarinic acid largely acts, offering a theoretical foundation for further studies on the application of OS in the prevention and treatment of illness as well as the preservation of kidney function.

SIGNIFICANCE

In this study, UHPLC-Q Exactive Orbitrap-HRMS was employed to discern OS's chemical composition, and a rapid, sensitive, and broad-coverage AFADESI-MSI method was developed to visualize the spatial distribution of compounds in tissues.

A Review on Berry Seeds—A Special Emphasis on Their Chemical Content and Health-Promoting Properties

Berries are important components of the human diet, valued for their high content of nutrients and active compounds. Berry seeds are also important objects of scientific investigation as, in some cases, they can have a higher concentration of certain phytochemicals than other parts of the fruit. Moreover, they are often byproducts of the food industry that can be reused to make oil, extracts, or flour. We have reviewed available literature related to the chemical content and biological activity of seeds from five different berry species—red raspberry (Rubus idaeus L. and Rubus coreanus Miq.), strawberry (Fragaria x ananassa), grape (Vitis vinifera L.), sea buckthorn (Hippophae rhamnoides L.), and cranberry (Vaccinium macrocarpon Ait.). We have searched various databases, including PubMed, Web of Knowledge, ScienceDirect, and Scopus. Last search was conducted on 16.01.2023. Various preparations from berry seeds are valuable sources of bioactive phytochemicals and could be used as functional foods or to make pharmaceuticals or cosmetics. Some products, like oil, flour, or extracts, are already available on the market. However, many preparations and compounds still lack appropriate evidence for their effectiveness in vivo, so their activity should first be assessed in animal studies and clinical trials.

Pharmacokinetic Differences of Wuji Pill Components in Normal and Chronic Visceral Hypersensitivity Irritable Bowel Syndrome Rats Attributable to Changes in Tight Junction and Transporters

The Wuji pill, also called Wuji Wan (WJW), is an effective traditional medicine for the clinical treatment of irritable bowel syndrome (IBS). It is principally composed of Rhizoma Coptidis, Fructus Evodiae Rutaecarpae, and Radix Paeoniae Alba. There have been no reports on the pharmacokinetics of WJW on IBS. Because it is more meaningful to study pharmacokinetics in relation to specific pathological conditions, our study investigated the pharmacokinetic differences of five representative components (berberine, palmatine, evodiamine, rutaecarpine, and paeoniflorin) in normal rats and chronic visceral hypersensitivity IBS (CVH-IBS) model rats after single dose and multiple doses of WJW using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Transmission electron microscopy, immunohistochemistry, and immunofluorescence were used to explore mechanisms behind the pharmacokinetic differences in terms of tight junction proteins (Occludin and ZO-1), myosin light chain kinase (MLCK), and transporters including P-glycoprotein (P-gp), multidrug resistance associated protein 1 (MRP1), and multidrug resistance associated protein 2 (MRP2) in rat colons. After a single dose, for all components except rutaecarpine, significant differences were observed between normal and model groups. Compared with normal group, T_1/2 and AUC_0-t of berberine and palmatine in model group increased significantly (562.5 ± 237.2 vs. 1,384.9 ± 712.4 min, 733.8 ± 67.4 vs. 1,532.4 ± 612.7 min; 5,443.0 ± 1,405.8 vs. 9,930.8 ± 2,304.5 min·ng/ml, 2,365.5 ± 410.6 vs. 3,527.0 ± 717.8 min·ng/ml), while Cl/F decreased (840.7 ± 250.8 vs. 397.3 ± 142.7 L/h/kg, 427.7 ± 89.4 vs. 288.9 ± 114.4 L/h/kg). C_max and AUC_0-t of evodiamine in model group increased significantly (1.4 ± 0.6 vs. 2.4 ± 0.7 ng/ml; 573 ± 45.3 vs. 733.9 ± 160.2 min·ng/ml), while T_1/2, T_max, Cl/F, and Vd/F had no significant difference. T_max and AUC_0-t of paeoniflorin in model group increased significantly (21.0 ± 8.2 vs. 80.0 ± 45.8 min; 15,428.9 ± 5,063.6 vs. 33,140.6 ± 5,613.9 min·ng/ml), while Cl/F decreased (110.5 ± 48.1 vs. 43.3 ± 9.5 L/h/kg). However, after multiple doses, all five components showed significant differences between normal and model groups. Moreover, these differences were related to tight junction damage and the differential expression of transporters in the colon, suggesting that dose adjustment might be required during administration of WJW in the clinical treatment of IBS.

Acute Developmental Toxicity of Panax notoginseng in Zebrafish Larvae

OBJECTIVE

To evaluate toxicity of raw extract of Panax notoginseng (rPN) and decocted extract of PN (dPN) by a toxicological assay using zebrafish larvae, and explore the mechanism by RNA sequencing assay.

METHODS

Zebrafish larvae was used to evaluate acute toxicity of PN in two forms: rPN and dPN. Three doses (0.5, 1.5, and 5.0 µ g/mL) of dPN were used to treat zebrafishes for evaluating the developmental toxicity. Behavior abnormalities, body weight, body length and number of vertebral roots were used as specific phenotypic endpoints. RNA sequencing (RNA-seq) assay was applied to clarify the mechanism of acute toxicity, followed by real time PCR (qPCR) for verification. High performance liquid chromatography analysis was performed to determine the chemoprofile of this herb.

RESULTS

The acute toxicity result showed that rPN exerted higher acute toxicity than dPN in inducing death of larval zebrafishes (P<0.01). After daily oral intake for 21 days, dPN at doses of 0.5, 1.5 and 5.0 µ g/mL decreased the body weight, body length, and vertebral number of larval zebrafishes, indicating developmental toxicity of dPN. No other adverse outcome was observed during the experimental period. RNA-seq data revealed 38 genes differentially expressed in dPN-treated zebrafishes, of which carboxypeptidase A1 (cpa1) and opioid growth factor receptor-like 2 (ogfrl2) were identified as functional genes in regulating body development of zebrafishes. qPCR data showed that dPN significantly down-regulated the mRNA expressions of cpa1 and ogfrl2 (both P<0.01), verifying cpa1 and ogfrl2 as target genes for dPN.

CONCLUSION

This report uncovers the developmental toxicity of dPN, suggesting potential risk of its clinical application in children.

Pharmacokinetic interaction between peimine and paeoniflorin in rats and its potential mechanism

CONTEXT

Peimine and paeoniflorin can be combined for the treatment of cough in paediatrics. The interaction during the co-administration could dramatically affect the bioavailability of drugs.

OBJECTIVE

The interaction between peimine and paeoniflorin was investigated in this study.

MATERIALS AND METHODS

The pharmacokinetics of paeoniflorin (20 mg/kg) with or without the coadministration of peimine (5 mg/kg for 10 days before paeoniflorin) was orally investigated in Sprague-Dawley rats (n = 6). The group without the peimine was set as the control group. The metabolic stability of paeoniflorin was studied in rat liver with microsomes. The effect of peimine on the absorption of paeoniflorin was investigated with Caco-2 cell monolayers.

RESULTS

The C_max (244.98 ± 10.95 vs. 139.18 ± 15.14 μg/L) and AUC_(0-t) (3295.92 ± 263.02 vs. 139.18 ± 15.14 h·μg/L) of paeoniflorin was increased by peimine. The t_1/2 was prolonged from 5.33 ± 1.65 to 14.21 ± 4.97 h and the clearance was decreased from 15.43 ± 1.75 to 4.12 ± 0.57 L/h/kg. Consistently, peimine increased the metabolic stability of paeoniflorin with rat liver microsomes with the increased t_1/2 (56.78 ± 2.62 vs. 26.33 ± 3.15 min) and the decreased intrinsic clearance (24.42 ± 3.78 vs. 52.64 ± 4.47 μL/min/mg protein). Moreover, the transportation of paeoniflorin was also inhibited by peimine as the efflux ratio decreased from 3.06 to 1.63.

DISCUSSION AND CONCLUSIONS

Peimine increased the systemic exposure of paeoniflorin through inhibiting the activity of CYP3A4 and P-gp. These results provide a reference for further in vivo studies in a broader population.

Extract from Dioscorea bulbifera L. rhizomes aggravate pirarubicin-induced cardiotoxicity by inhibiting the expression of P-glycoprotein and multidrug resistance-associated protein 2 in the mouse liver

Chinese herbal medicine is widely used because it has a good safety profile and few side effects. However, the risk of adverse drug reactions caused by herb-drug interactions (HDIs) is often overlooked. Therefore, the task of identifying possible HDIs and elucidating their mechanisms is of great significance for the prevention and treatment of HDI-related adverse reactions. Since extract from Dioscorea bulbifera L. rhizomes (DB) can cause various degrees of liver damage, it is speculated that HDIs may occur between DB extract and chemicals metabolized or excreted by the liver. Our study revealed that the cardiotoxicity of pirarubicin (THP) was increased by co-administration of DB, and the expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (Mrp2) in the liver was inhibited by DB extract, which led to the accumulation of THP in heart tissue. In conclusion, there are risks of the co-administration of DB extract and THP. The mechanism of HDIs can be better revealed by targeting the efflux transporters.

UPLC-MS/MS method for the simultaneous quantification of pravastatin, fexofenadine, rosuvastatin, and methotrexate in a hepatic uptake model and its application to the possible drug-drug interaction study of triptolide

A rapid and specific UPLC-MS/MS method with a total run time of 3.5 min was developed for the determination of pravastatin, fexofenadine, rosuvastatin, and methotrexate in rat primary hepatocytes. After protein precipitation with 70% acetonitrile (containing 30% H2 O), these four analytes were separated under gradient conditions with a mobile phase consisting of 0.03% acetic acid (v/v) and methanol at a flow rate of 0.50 mL/min. The linearity, recovery, matrix effect, accuracy, precision, and stability of the method were well validated. We evaluated drug-drug interactions based on these four compounds in freshly suspended hepatocytes. The hepatic uptake of pravastatin, fexofenadine, rosuvastatin, and methotrexate at 4°C was significantly lower than that at 37°C, and the hepatocytes were saturable with increased substrate concentration and culture time, suggesting that the rat primary hepatocyte model was successfully established. Triptolide showed a significant inhibitory effect on the hepatic uptake of these four compounds. In conclusion, this method was successfully employed for the quantification of pravastatin, fexofenadine, rosuvastatin, and methotrexate and was used to verify the rat primary hepatocyte model for Oatp1, Oatp2, Oatp4, and Oat2 transporter studies. Then, we applied this model to explore the effect of triptolide on these four transporters.

Glabrone as a specific UGT1A9 probe substrate and its application in discovering the inhibitor glycycoumarin

UDP-glucuronosyltransferase 1A9 (UGT1A9) is one of the most important UGT isoforms, and plays an important role in the metabolic elimination of therapeutic drugs via glucuronidation. Herbal medicines affecting the activity of UGT1A9 may influence the metabolism of related drugs, thus causing herb-drug interactions and even adverse effects. However, few methods are available to evaluate the activity of UGT1A9. In this study, a natural product glabrone was discovered as an isoform-specific probe substrate for UGT1A9. The V_max and K_m values of glabrone were 362.6 nmol/min/mg protein and 17.2 μM for human liver microsomes (HLMs), and 382.3 nmol/min/mg protein and 16.6 μM for recombinant human UGT1A9, respectively. Glabrone 7-O-glucuronide, the UGT1A9 metabolite of glabrone, was prepared by using a plant glucuronosyltransferase UGT88D1, and the structure was identified by NMR spectroscopy. Using glabrone as a probe, we established a rapid HPLC method to screen UGT1A9 inhibitors from 54 natural products isolated from the Chinese herbal medicine licorice. Among them, glycycoumarin was found as a potent UGT1A9 inhibitor with an IC₅₀ value of 6.04 μM. In rats, the pretreatment of glycycoumarin (4 mg/kg, i.p.) for 3 days could remarkably increase the plasma concentrations of dapagliflozin while decrease the concentrations of dapagliflozin-O-glucuronide after administration of dapagliflozin (1 mg/kg, i.v.), which is mainly metabolized by UGT1A9. The results indicated the potential risk of herb-drug interactions between licorice and UGT1A9-metabolizing drugs.

Research Progress of Herbal Medicines on Drug Metabolizing Enzymes: Consideration Based on Toxicology

The clinical application of herbal medicines is increasing, but there is still a lack of comprehensive safety data and in-depth research into mechanisms of action. The composition of herbal medicines is complex, with each herb containing a variety of chemical components. Each of these components may affect the activity of metabolizing enzymes, which may lead to herb-drug interactions. It has been reported that the combined use of herbs and drugs can produce some unexpected interactions. Therefore, this study reviews the progress of research on safety issues caused by the effects of herbs on metabolizing enzymes with reference to six categories of drugs, including antithrombotic drugs, non-steroidal anti-inflammatory drugs, anti-diabetic drugs, statins lipid-lowering drugs, immunosuppressants, and antineoplastic drugs. Understanding the effects of herbs on the activity of metabolizing enzymes could help avoid the toxicity and adverse drug reactions resulting from the co-administration of herbs and drugs, and help doctors to reduce the risk of prescription incompatibility.

Development and Validation of Liquid Chromatography-mass Spectrometry Method for the Determination of Intracellular Concentration of Ginkgolide A, B, C, and Bilobalide in Transporter-Expressing Cells

Background:

Terpene lactones are major components of ginkgo biloba extract which are used in cardiovascular and degenerative diseases. To study the involvement of transporters in the transport/disposition of ginkgolides A, B, C, and bilobalide, a bioanalytical assay was developed by LCMS/ MS system for the quantitation of intracellular levels of terpene lactones in cells expressing organic cation transporter 2 (OCT2).

Methods:

The assay involved an optimized simple sample handling with methyl tert-butyl ether for liquid-liquid extraction and reconstitution in modified dissolution solution. Pretreatment of samples with 50 μM ascorbic acid and the addition of ascorbic acid and formic acid in dissolution solution significantly reduced matrix effect and stabilized the postpreparative samples. Separations were performed by Zobrax RRHD column (extend-C18 1.8μm, 3.0 x 100mm) and acetonitrile gradient elution. The analysis was carried out in the negative ion scan mode using multiple reaction monitoring.

Results:

The method was validated for linearity (concentration range of 20-5000nM), accuracy (±13.1%), precision (<11.0%), recovery (94.31–105.9%), matrix effect (93.8-111.0%) and stability. Finally, the method was applied in the determination of intracellular concentrations of ginkgolides A, B, C, and bilobalide in Madin-Darby canine kidney (MDCK-mock) and MDCK-OCT2 cells in uptake study.

Conclusion:

The developed method was successfully validated. Results suggest that OCT2 is involved in the renal disposition of ginkgolide A, B, and bilobalide. This method would foster the study of transport mediated activity via the interaction of ginkgolides and bilobalide with cellular systems.

Inhibitory Effect of Lygodium Root on the Cytochrome P450 3A Enzyme in vitro and in vivo

Purpose

The aim of the present study was to investigate the interactions of the main components of Lygodium root (ie, p-coumaric acid, acacetin, apigenin, buddleoside and Diosmetin-7-O-β-D-glucopyranoside) with cytochrome P450 3A enzyme activity both in vitro and in vivo.

Methods

In vitro inhibition of drugs was assessed by incubating rat liver microsomes (RLMs) with a typical P450 3A enzyme substrate, midazolam, to determine their 50% inhibitory concentration (IC50) values. For the in vivo study, healthy male Sprague Dawley rats were consecutively administered acacetin or apigenin for 7 days at the dosage of 5 mg/kg after being randomly divided into 3 groups: Group A (control group), Group B (acacetin group) and Group C (apigenin group).

Results

Among the five main components of Lygodium root, only acacetin and apigenin showed inhibitory effects on the cytochrome P450 3A enzyme in vitro. The IC50 values of acacetin and apigenin were 58.46 μM and 8.20 μM, respectively. Additionally, the in vivo analysis results revealed that acacetin and apigenin could systemically inhibit midazolam metabolism in rats. The T_max, AUC_(0-t) and C_max of midazolam in group B and group C were significantly increased (P<0.05), accompanied by a significant decrease in V_z/F and CL_z/F (P<0.05).

Conclusion

Acacetin and apigenin could inhibit the activity of the cytochrome P450 3A enzyme in vitro and in vivo, indicating that herbal drug interactions might occur when taking Lygodium root and midazolam synchronously.

Evaluation of potential herbal-drug interactions of a standardized propolis extract (EPP-AF®) using an in vivo cocktail approach

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis has been employed extensively in many cultures since ancient times as antiseptic, wound healing, anti-pyretic and others due to its biological and pharmacological properties, such as immunomodulatory, antitumor, anti-inflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities. But despite its broad and traditional use, there is little knowledge about its potential interaction with prescription drugs.

AIM OF THE STUDY

The main objective of this work was to study the potential herbal-drug interactions (HDIs) of EPP-AF® using an in vivo assay with a cocktail approach.

MATERIALS AND METHODS

Subtherapeutic doses of caffeine, losartan, omeprazole, metoprolol, midazolam and fexofenadine were used. Sixteen healthy adult volunteers were investigated before and after exposure to orally administered 125 mg/8 h (375 mg/day) EPP-AF® for 15 days. Pharmacokinetic parameters were calculated based on plasma concentration versus time (AUC) curves.

RESULTS

After exposure to EPP-AF®, it was observed decrease in the AUC^0-∞ of fexofenadine, caffeine and losartan of approximately 18% (62.20 × 51.00 h.ng/mL), 8% (1085 × 999 h.ng/mL) and 13% (9.01 × 7.86 h.ng/mL), respectively, with all 90% CIs within the equivalence range of 0.80-1.25. On the other hand, omeprazole and midazolam exhibited an increase in AUC^0-∞ of, respectively, approximately 18% (18.90 × 22.30 h.ng/mL) and 14% (1.25 × 1.43 h.ng/mL), with the upper bounds of 90% CIs slightly above 1.25. Changes in pharmacokinetics of metoprolol or its metabolite α-hydroxymetoprolol were not statistically significant and their 90% CIs were within the equivalence range of 0.80-1.25.

CONCLUSIONS

In conclusion, our study shows that EPP-AF® does not clinically change CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A activities, once, despite statistical significant, the magnitude of the changes in AUC values after EPP-AF® were all below 20% and therefore may be considered safe regarding potential interactions involving these enzymes. Besides, to the best of our knowledge this is the first study to assess potential HDIs with propolis.

Mucoadhesive effect of Curcuma longa extract and curcumin decreases the ranitidine effect, but not bismuth subsalicylate on ethanol-induced ulcer model

The study of pharmacological interactions between herbal remedies and conventional drugs is important because consuming traditional herbal remedies as supplements or alternative medicine is fairly common and their concomitant administration with prescribed drugs could either have a favorable or unfavorable effect. Therefore, this work aims to determine the pharmacological interactions of a turmeric acetone extract (TAE) and its main metabolite (curcumin) with common anti-ulcer drugs (ranitidine and bismuth subsalicylate), using an ethanol-induced ulcer model in Wistar rats. The analysis of the interactions was carried out via the Combination Index-Isobologram Equation method. The combination index (CI) calculated at 0.5 of the affected fraction (fa) indicated that the TAE or curcumin in combination with ranitidine had a subadditive interaction. The results suggest that this antagonistic mechanism is associated to the mucoadhesion of curcumin and the TAE, determined by rheological measurements. Contrastingly, both the TAE and curcumin combined with bismuth subsalicylate had an additive relationship, which means that there is no pharmacological interaction. This agrees with the normalized isobolograms obtained for each combination. The results of this study suggest that mucoadhesion of curcumin and the TAE could interfere in the effectiveness of ranitidine, and even other drugs.

Effect of Naoxintong Capsules on the Activities of CYP450 and Metabolism of Metoprolol Tartrate in Rats Evaluated by Probe Cocktail and Pharmacokinetic Methods

Naoxintong capsule (NXT), a prescribed Chinese medicine, has been used clinically for more than 20 years and is widely received by patients. We determined five probe drugs, namely, omeprazole (CYP2C19), midazolam (CYP3A4), phenacetin (CYP1A2), tolbutamide (CYP2C9), and dextromethorphan (CYP2D6) to study the potential influences of NXT on the activities of CYP enzymes and assessed the pharmacokinetics effect of NXT on metoprolol tartrate in rat plasma. The study showed that AUC_(0–24) and AUC_(0–∞) of midazolam (CYP3A4) in NXT coadministration group (283.7 ± 65.2 h·ng·mL⁻¹ and 292.0 ± 75.1 h·ng·mL⁻¹ in group B; 295.7 ± 62.7 h·ng·mL⁻¹ and 299.5 ± 60.0 h·ng·mL⁻¹ in group C) were significantly decreased as compared to another group (416.8 ± 82.3 h·ng·mL⁻¹ and 424.9 ± 77.9 h·ng·mL⁻¹ in group A), while that of dextromethorphan (CYP2D6) showed an opposite tendency (540.7 ± 119.7 h·ng·mL⁻¹ and 595.3 ± 122.2 h·ng·mL⁻¹ in group A, 760.6 ± 184.9 h·ng·mL⁻¹ and 788.7 ± 211.0 h·ng·mL⁻¹ in group B, and 734.3 ± 118.5 h·ng·mL⁻¹ and 757.2 ± 105.4 h·ng·mL⁻¹ in group C). Moreover, NXT preadministration can enhance the metabolism of metoprolol tartrate and reduce the metabolism of O-demethylmetoprolol. The results indicated that NXT had potential effects in inducing CYP3A4 and inhibiting CYP2D6 in the metabolism of metoprolol tartrate. It suggests that patients who coadministered NXT and metoprolol tartrate should be advised of potential herb-drug interactions (HDIs) to reduce therapeutic failure or accelerated toxicity of conventional drug treatment.

Influence of organic anion transporter 1/3 on the pharmacokinetics and renal excretion of ginkgolides and bilobalide

ETHNOPHARMACOLOGICAL RELEVANCE

The major terpene lactones of ginkgo biloba extract (GBE) include ginkgolide A, B, C and bilobalide are used for the protection of cardiovascular, cerebrovascular and neurodegenerative diseases. Terpene lactones are orally bioavailable and predominantly eliminated via the renal pathway. However, information on the transporters involved in the pharmacokinetics (PK) and renal excretion of terpene lactones is limited.

AIM OF THE STUDY

The objective of this study is to assess the role of OAT1/3 which are important transporters in the human kidney in the PK and renal excretion ginkgolide A, B, C and bilobalide.

MATERIALS AND METHODS

Uptake of ginkgolide A, B, C and bilobalide in Madin-Darby Canine Kidney (MDCK) and human embryonic kidney 293 (HEK293) cells overexpressing OAT1 or OAT3, respectively were studied. To verify the result from in vitro cell models, the studies on PK, kidney accumulation and urinary excretion of ginkgolide A, B, C and bilobalide were carried out in rats.

RESULTS

The result showed that ginkgolide A, B, C and bilobalide are low-affinity substrates of OAT1/3. Following co-administration with probenecid, a typical inhibitor of OAT1/3, the rat plasma concentrations of ginkgolide A, B, C and bilobalide increased significantly. AUC showed a significant increase in the probenecid-treated rats compared to control rats (893.48 vs. 1123.85, 314.91 vs. 505.74, and 2724.97 vs. 3096.40 μg/L*h for ginkgolide A, B and bilobalide, respectively), while the clearance of these compounds significantly decreased. The accumulation of ginkgolide A, B and bilobalide in the kidney of the probenecid-treated rats was reduced by 1.8, 2.4, and 1.5-fold, respectively; further reducing the cumulative urinary recovery of these compounds.

CONCLUSION

The findings indicated that ginkgolide A, B and bilobalide are excreted via OAT1/3-mediated transport in the kidney and OAT1/3 inhibitor significantly influence the PK ginkgolides and bilobalide.

Reviewing the mechanisms of natural product-drug interactions involving efflux transporters and metabolic enzymes

The World Health Organization (WHO) and other worldwide health agencies have recently taken initiatives to encourage the use of traditional medicine and/or complementary/alternative medicine in order to promote well-being and public health. In this way, one of the WHO's concerns is the safe use of these therapies. Phytotherapy is a strategy consisting of the use of medicinal plants (MP) and/or herbal medicinal products (HMP) for medicinal purposes. The use of phytotherapy concomitantly with drugs may cause interactions compromising the expected pharmacological action or generating toxic effects. These interactions are complex processes that may occur with multiple medications targeting different metabolic pathways, and involving different compounds present in MP and HMP. Thus, the aim of this review was to summarize the main MP- and HMP-drug interactions that involve specific transporters (P-glycoprotein and BCRP) and CYP450 enzymes (CYP3A4 and CYP2D6), which play relevant roles in the mechanisms of interactions. Firstly, multiple databases were used to search studies describing in vitro or in vivo MP and HMP-drug interactions and, after that, a systematic note-taking and appraisal of the literature was conducted. It was observed that several MP and HMP, metabolic pathways and transcription factors are involved in the transporters and enzymes expression or in the modulation of their activity having the potential to provide such interactions. Thus, the knowledge of MP- and HMP-drug interaction mechanisms could contribute to prevent harmful interactions and can ensure the safe use of these products to help the establishment of the therapeutic planning in order to certify the best treatment strategy to be used.

Lonicera japonica extract increases metformin distribution in the liver without change of systemic exposed metformin in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Flower and flower bud of Lonicera japonica, Lonicerae Flos, have been popularly used as medicinal plant for the treatment of clearing heat and thirst, thereby improving diabetic or diabetic associated symptoms (thirst and poor eyesight).

AIM OF THE STUDY

Organic cation transporters (OCTs) and multi-drug and toxin extrusion proteins (MATEs) are known to play important roles in metformin transport in the liver and kidneys. Thus, there might be interactions between Lonicerae Flos and metformin via OCTs and MATEs. Also treatment period has been issued in transporter-mediated drug interactions. The objective of this study was to determine the effect of Lonicerae Flos ethanol extract (LJ) on metformin pharmacokinetics and its glucose lowering activity in different treatment periods.

MATERIALS AND METHODS

Effect of LJ on metformin uptake was evaluated in vitro HEK-293 cells expressing human OCTs or MATEs. Treatment period-dependent impact of LJ on systemic exposure and hepatic distribution of metformin as well as its glucose tolerance activity were assessed in in vivo rats.

RESULTS

LJ substantially inhibited MATE1-mediated metformin uptake in vitro. In evaluating treatment period effects of LJ and metformin, 1-, 7-, and 28-day co-treatments of LJ with metformin did not change systemic exposure of metformin compared to those in metformin alone. Whereas, 28-day co-treatment of LJ with metformin increased metformin concentration in liver as a pharmacological target site of metformin. It could be due to the reduced MATE1-mediated metformin efflux from hepatocytes to bile by MATE1 inhibition in liver. Glucose tolerance activity was also enhanced by 28-day co-treatment of LJ and metformin compared to metformin alone.

CONCLUSIONS

In 28-day co-treatment of LJ and metformin, LJ increased metformin concentration in liver and improved glucose tolerance activity without systemic exposure change of metformin, suggesting the importance to consider treatment period effect and both systemic exposure and tissue distribution in drug interactions.

Development of Caco-2 cells-based gene reporter assays and evaluation of herb-drug interactions involving CYP3A4 and CYP2D6 gene expression

The indiscriminate use of medicinal plants and herbal medicinal products concomitantly with conventional drugs may result in herb-drug interactions that may lead to fluctuations in drug bioavailability, therapeutic failure, and/or toxic effects. CYP450 enzymes play an important role in drug biotransformation and herb-drug interactions. Thus, the aim of this study was to develop and apply Caco-2 cells-based gene reporter assays to study in vitro the potential occurrence of CYP3A4 and CYP2D6 gene expression modulation by standardized extracts of selected medicinal plants. Reporter cell lines developed showed a significant increase in CYP3A4 and CYP2D6 reporter fluorescent emission, 4 and 16-fold respectively, when compared to the controls. The standardized extracts of Cecropia glaziovii, Bauhinia forficata and Echinacea sp. significantly increased CYP3A4 reporter fluorescence, and those of Ilex paraguariensis, Bauhinia forficata and Echinacea sp. significantly decreased CYP2D6 reporter fluorescence in Caco-2 cells-based gene reporter assays. The data obtained suggest that CYP3A4 and CYP2D6 gene expression seem to be modulated by the extracts tested. In addition, the reporter cell lines developed are functional assays that could be used to study drug-drug and herb-drug interactions during the research and development of new drugs.

In Vivo Modulation of Rat Liver Microsomal Cytochrome P450 Activity by Antimalarial, Anti-HIV, and Antituberculosis Plant Medicines

Drug interactions are key reasons for adverse drug reactions and attrition from market. Major infectious diseases causing morbidity/mortality in Ghana are malaria, tuberculosis, and HIV/AIDS. In this study, plant medicines commonly used to treat/manage these diseases in Ghana were investigated for their potential to modulate rat cytochrome P450 enzyme activities. Fluorescence and high-performance liquid chromatography-based assays were used to assess effects of antimalarial plant medicines, Fever (FEV), Mal-TF (MAL), and Kantinka terric (KT); anti-TB medicines, Chestico (CHES), CA + ST Pains + HWNT (TF), and Kantinka herbatic (KHB); and anti-HIV/AIDS medicines, Wabco (WAB), AD + T/AD (LIV) and Kantinka BA (KBA) on rat liver microsomal cytochrome P450 enzyme activities. Effects of medicines on rat biochemical and hematological parameters were also assessed. Generally, the medicines altered microsomal CYP1A1/1A2, CYP2B1/2B2, CYP2C9, and CYP2D6 activities. Only KBA elicited an increase (80%) in CYP1A1/1A2 activity. FEV, MAL, CHES, WAB, and LIV strongly inhibited the enzyme activity. All the medicines significantly inhibited CYP2C9 (24%-80%) activity. CYP2D6 activity increased after treatment with MAL, KBA, LIV, and TF. Also, MAL, WAB, LIV, KHB, and CHES increased CYP2B1/2B2 activity, while KT decrease the activity. Generally, the medicines altered liver function in the rats. Cholesterol levels declined after KBA treatment only. White and red blood cell counts, hemoglobin and hematocrit levels were significantly reduced in KT- and KBA-treated rats. Our results suggest that use of the medicines could have implications for drug interactions and safety, particularly if the medicines are administered over prolonged periods. Further investigations are imperative to establish clinical relevance of these results.

Effects of Panax Notoginseng Saponins on Esterases Responsible for Aspirin Hydrolysis In Vitro

Herb–drug interactions strongly challenge the clinical combined application of herbs and drugs. Herbal products consist of complex pharmacological-active ingredients and perturb the activity of drug-metabolizing enzymes. Panax notoginseng saponins (PNS)-based drugs are often combined with aspirin in vascular disease treatment in China. PNS was found to exhibit inhibitory effects on aspirin hydrolysis using Caco-2 cell monolayers. In the present study, a total of 22 components of PNS were separated and identified by UPLC-MS/MS. Using highly selective probe substrate analysis, PNS exerted robust inhibitory potency on human carboxylesterase 2 (hCE2), while had a minor influence on hCE1, butyrylcholinesterase (BChE) and paraoxonase (PON). These effects were also verified through molecular docking analysis. PNS showed a concentration-dependent inhibitory effect on hydrolytic activity of aspirin in HepaRG cells. The protein level of hCE2 in HepaRG cells was suppressed after PNS treatment, while the level of BChE or PON1 in the extracellular matrix were elevated after PNS treatment. Insignificant effect was observed on the mRNA expression of the esterases. These findings are important to understand the underlying efficacy and safety of co-administration of PNS and aspirin in clinical practice.

Eugenia jambolana extract reduces the systemic exposure of Sitagliptin and improves conditions associated with diabetes: A pharmacokinetic and a pharmacodynamic herb-drug interaction study

Eugenia jambolana (EJ) is an Indian traditional herb widely used for the treatment of diabetes mellitus. This herb is globally marketed as single or multi herb formulations. Many diabetes patients consume EJ extract oral hypoglycemic drugs together. This calls for a need to assess risks versus benefit of this co-administration.

In present investigation, pharmacodynamic and pharmacokinetic interactions of aqueous extract of EJ seeds at the dose of 400 mg/kg are studied with 10 mg/kg of oral hypoglycaemic drug sitagliptin (SITA) by co-administrating them for 28 days in streptozotocin (STZ) induced diabetic rats. The pharmacokinetic parameters of SITA were determined using HPLC-ESI-MS/MS and it was found that the combination treatment reduces the systemic exposure of SITA by showing 38.70% reduction in concentration maximum (Cmax) and 22.40% reduction in area under curve (AUC). Despite low levels of SITA, the combination demonstrated a significant reduction in blood glucose level when compared with individual drug and individual extract administered groups during pharmacodynamic study. In addition, the liver function, the kidney function and the lipid parameters were found to be significantly improved and beneficial effects were found with respect to food intake and water intake and urine output in case of combination treatment groups when compared with individual treatment groups. Histopathological examination of pancreatic tissue suggests its significant recovery of having normal acinus with better cell protection in combination treatment. In conclusion, the combination treatment demonstrated reduced systemic exposure of SITA without compromising on its antihyperglycemic activity and improvement in conditions associated with diabetes.

Herbal beverages: Bioactive compounds and their role in disease risk reduction - A review

There is a renewed interest in non-nutritive bioactive compounds of foods and beverages as 'lifespan nutrients' in the risk reduction of non-communicable diseases. Herbal beverages, consumed as part of a balanced diet, may improve the antioxidant status and enhance the overall health status. Herbal teas/beverages are rich sources of natural bioactive compounds such as carotenoids, phenolic acids, flavonoids, coumarins, alkaloids, polyacetylenes, saponins and terpenoids, among others. A wealth of available scientific evidence demonstrates that natural bioactive compounds render a number of diversified biological effects, such as antioxidant, antibacterial, antiviral, antiinflammatory, antiallergic, antithrombotic and vasodilatory actions, as well as antimutagenicity, anticarcinogenicity and antiaging effects. A number of herbal beverages are consumed globally and some beverages have gained more popularity than others depending on their geographical origin. However, in the era of globalization, ethnic barriers have gradually been removed and such commodities although from different areas, are now universally available as international health-pro products.

Daikenchuto (TU-100) alters murine hepatic and intestinal drug metabolizing enzymes in an in vivo dietary model: effects of gender and withdrawal

Herbal medicines and natural products used for maintenance of health or treatment of diseases have many biological effects, including altering the pharmacokinetics and metabolism of other medications. Daikenchuto (TU‐100), an aqueous extract of ginger, ginseng, and Japanese green pepper fruit, is a commonly prescribed Kampo (Japanese herbal medicine) for postoperative ileus or bloating. The effects of TU‐100 on drug metabolism have not been investigated. In this study, we analyzed the effect of TU‐100 on expression of key drug‐metabolizing enzymes (DMEs) and drug transporters (DTs) in murine liver and gastrointestinal tract using a dietary model. Liver, jejunum, and proximal colon were analyzed for phase I and II DMEs and DT mRNA expression by reverse transcription (RT) first by nonquantitative and followed by quantitative polymerase chain reaction (PCR) and protein expression. Liver, jejunum, and proximal colon expressed some identical but also unique DMEs and DTs. TU‐100 increased the greatest changes in cytochrome (Cyp) 2b10 and Cyp3a11 and Mdr1a. Basal and TU‐100 stimulated levels of DME and DT expression were gender‐dependent, dose‐dependent and reversible after cessation of TU‐100 supplementation, except for some changes in the intestine. Quantitative Western blot analysis of protein extracts confirmed the quantitative PCR results.

Enzyme Kinetics and Molecular Docking Studies on Cytochrome 2B6, 2C19, 2E1, and 3A4 Activities by Sauchinone

Sauchinone, an active lignan isolated from the aerial parts of Saururus chinensis (Saururaceae), exhibits anti-inflammatory, anti-obesity, anti-hyperglycemic, and anti-hepatic steatosis effects. As herb–drug interaction (HDI) through cytochrome P450s (CYPs)-mediated metabolism limits clinical application of herbs and drugs in combination, this study sought to explore the enzyme kinetics of sauchinone towards CYP inhibition in in vitro human liver microsomes (HLMs) and in vivo mice studies and computational molecular docking analysis. In in vitro HLMs, sauchinone reversibly inhibited CYP2B6, 2C19, 2E1, and 3A4 activities in non-competitive modes, showing inhibition constant (K_i) values of 14.3, 16.8, 41.7, and 6.84 μM, respectively. Also, sauchinone time-dependently inhibited CYP2B6, 2E1 and 3A4 activities in vitro HLMs. Molecular docking study showed that sauchinone could be bound to a few key amino acid residues in the active site of CYP2B6, 2C19, 2E1, and 3A4. When sibutramine, clopidogrel, or chlorzoxazone was co-administered with sauchinone to mice, the systemic exposure of each drug was increased compared to that without sauchinone, because sauchinone reduced the metabolic clearance of each drug. In conclusion, when sauchinone was co-treated with drugs metabolized via CYP2B6, 2C19, 2E1, or 3A4, sauchinone–drug interactions occurred because sauchinone inhibited the CYP-mediated metabolic activities.

Assessment of cytochrome P450 inhibition and induction potential of lupeol and betulin in rat liver microsomes

BACKGROUND

Lupeol and betulin are triterpenoids that are majorly found in dietary substances. The aim of present study was to investigate the inhibition and induction potential of lupeol and betulin on cytochrome P450 (CYP)1A2, CYP2C11, CYP2D6 and CYP3A2 activities in rat liver microsomes.

METHODS

The inhibition and induction studies were conducted using ethoxy resorufin-O-deethylase (CYP1A2), tolbutamide hydroxylase (CYP2C9), and midazolam hydroxylase (CYP3A4) activity assays. In vitro inhibition study was evaluated by incubating lupeol and betulin (1, 3, 10, 30 and 100 μM) with rat liver microsomes, and the metabolite formation was analyzed by high-performance liquid chromatography. The induction study was conducted by administering lupeol (20 mg/kg) and betulin (50 mg/kg) intraperitoneally for 14 days to rats followed by liver isolation and microsome preparation.

RESULTS

The IC50 values in inhibition studies were found to be 59.42 μM (CYP1A2), >100 μM (CYP2C11, CYP2D6, CYP3A2) for lupeol, 52.24 μM (CYP1A2), and >100 μM (CYP2C9, CYP2D6, CYP3A2) for betulin. There was no significant modification observed in the CYP450 isoforms, indicating neither inhibition nor induction potential of lupeol and betulin.

CONCLUSIONS

Lupeol and betulin have very low propensity to interact with CYP enzyme, suggesting no CYP inhibitory and inducing potential in rat liver microsomes.

Quality Assessment of Gentiana rigescens from Different Geographical Origins Using FT-IR Spectroscopy Combined with HPLC

Gentiana rigescens is a precious herbal medicine in China because of its liver-protective and choleretic effects. A method for the qualitative identification and quantitative evaluation of G. rigescens from Yunnan Province, China, has been developed employing Fourier transform infrared (FT-IR) spectroscopy and high performance liquid chromatography (HPLC) with the aid of chemometrics such as partial least squares discriminant analysis (PLS-DA) and support vector machines (SVM) regression. Our results indicated that PLS-DA model could efficiently discriminate G. rigescens from different geographical origins. It was found that the samples which could not be determined accurately were in the margin or outside of the 95% confidence ellipses. Moreover, the result implied that geographical origins variation of root samples were more obvious than that of stems and leaves. The quantitative analysis was based on gentiopicroside content which was the main active constituent in G. rigescens. For the prediction of gentiopicroside, the performances of model based on the parameters selected through grid search algorithm (GS) with seven-fold cross validation were better than those based on genetic algorithm (GA) and particle swarm optimization algorithm (PSO). For the SVM-GS model, the result was satisfactory. FT-IR spectroscopy coupled with PLS-DA and SVM-GS can be an alternative strategy for qualitative identification and quantitative evaluation of G. rigescens.

Chromatographic fingerprinting as a strategy to identify regulated plants in illegal herbal supplements

Erectile dysfunction (ED) is a sexual disorder characterized by the inability to achieve or maintain a sufficiently rigid erection. Despite the availability of non-invasive oral treatment options, many patients turn to herbal alternatives. Furthermore, herbal supplements are increasingly gaining popularity in industrialized countries and, as a consequence, quality control is a highly important issue. Unfortunately, this is not a simple task since plants are often crushed and mixed with other plants, which complicates their identification by usage of classical approaches such as microscopy. The aim of this study was to explore the potential use of chromatographic fingerprinting to identify plants present in herbal preparations intended for the treatment of ED. To achieve this goal, a HPLC-PDA and a HPLC-MS method were developed, using a full factorial experimental design in order to acquire characteristic fingerprints of three plants which are potentially beneficial for treating ED: Epimedium spp., Pausinystalia yohimbe and Tribulus terrestris. The full factorial design demonstrated that for all three plant references a C8 column (250mm×4.6mm; 5µm particle size) is best suited; methanol and an ammonium formate buffer (pH 3) were found to be the best constituents for the mobile phase. The suitability of this strategy was demonstrated by analysing several self-made triturations in three different botanical matrices, which mimic the influential effects that could be expected when analysing herbal supplements. To conclude, this study demonstrates that chromatographic fingerprinting could provide a useful means to identify plants in a complex herbal mixture.

Glycyrrhetinic acid might increase the nephrotoxicity of bakuchiol by inhibiting cytochrome P450 isoenzymes

Background

Licorice, a popular traditional Chinese medicine (TCM), is widely used to moderate the effects (detoxification) of other herbs in TCM and often combined with Fructus Psoraleae. However, the classical TCM book states that Fructus Psoraleae is incompatible with licorice; the mechanism underlying this incompatibility has not been identified. Glycyrrhetinic acid (GA), the active metabolite of licorice, may increase the toxicity of bakuchiol (BAK), the main chemical ingredient in Psoralea corylifolia, by inhibiting its detoxification enzymes CYP450s.

Methods

The effect of concomitant GA administration on BAK-induced nephrotoxicity was investigated, and the metabolic interaction between BAK and GA was further studied in vitro and in vivo. The cytotoxicity was assessed using an MTT assay in a co-culture model of HK-2 cell and human liver microsomes (HLMs). The effect of GA on the metabolism of BAK, and on the activities of CYP isoforms were investigated in HLMs. The toxicokinetics and tissue exposure of BAK as well as the renal and hepatic functional markers were measured after the administration of a single oral dose in rats.

Results

In vitro studies showed that the metabolic detoxification of BAK was significantly reduced by GA, and BAK was toxic to HK-2 cells, as indicated by 25∼40% decreases in viability when combined with GA. Further investigation revealed that GA significantly inhibited the metabolism of BAK in HLMs in a dose-dependent manner. GA strongly inhibits CYP3A4 and weakly inhibits CYP2C9 and CYP1A2; these CYP isoforms are involved in the metabolism of BAK. In vivo experiment found that a single oral dose of BAK combined with GA or in the presence of 1-aminobenzotriazole (ABT), altered the toxicokinetics of BAK in rats, increased the internal exposure, suppressed the elimination of BAK prototype, and therefore may have enhanced the renal toxicity.

Conclusion

The present study demonstrated that GA inhibits CYP isoforms and subsequently may increase the nephrotoxicity of BAK, which underlie one of the possible mechanisms responsible for the incompatibility of Licorice with Fructus Psoraleae.

Comparison of mercury sulfides with mercury chloride and methylmercury on hepatic P450, phase-2 and transporter gene expression in mice

Zuotai (mainly β-HgS) and Zhusha (also called as cinnabar, mainly α-HgS) are used in traditional medicines in combination with herbs or even drugs in the treatment of various disorders, while mercury chloride (HgCl2) and methylmercury (MeHg) do not have known medical values but are highly toxic. This study aimed to compare the effects of mercury sulfides with HgCl2 and MeHg on hepatic drug processing gene expression. Mice were orally administrated with Zuotai (β-HgS, 30mg/kg), α-HgS (HgS, 30mg/kg), HgCl2 (33.6mg/kg), or MeHg (3.1mg/kg) for 7days, and the expression of genes related to phase-1 drug metabolism (P450), phase-2 conjugation, and phase-3 (transporters) genes were examined. The mercurials at the dose and duration used in the study did not have significant effects on the expression of cytochrome P450 1-4 family genes and the corresponding nuclear receptors, except for a slight increase in PPARα and Cyp4a10 by HgCl2. The expressions of UDP-glucuronosyltransferase and sulfotransferase were increased by HgCl2 and MeHg, but not by Zuotai and HgS. HgCl2 decreased the expression of organic anion transporter (Oatp1a1), but increased Oatp1a4. Both HgCl2 and MeHg increased the expression of multidrug resistance-associated protein genes (Mrp1, Mrp2, Mrp3, and Mrp4). Zuotai and HgS had little effects on these transporter genes. In conclusion, Zuotai and HgS are different from HgCl2 and MeHg in hepatic drug processing gene expression; suggesting that chemical forms of mercury not only affect their disposition and toxicity, but also affect their effects on the expression of hepatic drug processing genes.

Regulation of drug-metabolizing enzymes and efflux transporters by Astragali radix decoction and its main bioactive compounds: Implication for clinical drug-drug interactions

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali radix ("Huang Qi" in Chinese, HQ) is a well-known traditional Chinese herbal medicine that possesses various biological functions. Astragaloside IV (AS-IV), calycosin (CS), and formononetin (FMNT) are the three main bioactive compounds of HQ that are responsible for its pharmacological activities and therapeutic efficacy.

AIM OF THE STUDY

This study aims to investigate the effects of HQ, AS-IV, CS, and FMNT on major human drug-metabolizing enzymes (DMEs), including CYP3A4, CYP2B6, CYP2E1, UGT1A, UGT1A6, SULT1A1, and SULT1A3, as well as efflux transporters (ETs), including P-gp, MRP2, BCRP, MRP1, and MRP3, by using HepG2 cell line. Results would provide beneficial information for the proper clinical application of HQ.

MATERIALS AND METHODS

HepG2 cells were treated with HQ, AS-IV, CS, and FMNT for 96h. Cell viability was examined by MTT assay. The protein and mRNA levels of DMEs and ETs were measured using Western blot and real-time PCR, respectively.

RESULTS

Compared with the control group, HQ considerably increased the expression levels of CYP3A4, CYP2B6, CYP2E1, UGT1A, P-gp, MRP2, BCRP, and MRP3 in a dose-dependent manner. Inversely, HQ significantly decreased the protein levels of UGT1A6, SULT1A1, and MRP1. Exposure to AS-IV induced the protein levels of UGT1A, P-gp, MRP1, and MRP3, but produced inhibitory effects on CYP3A4, CYP2B6, and BCRP. The expression levels of CYP3A4, UGT1A, SULT1A1, P-gp, MRP2, and MRP3 were remarkably increased in the CS-treated cells, whereas the protein levels of SULT1A3 and BCRP were decreased. FMNT treatment induced the protein levels towards CYP3A4, CYP2B6, UGT1A, P-gp, MRP1, MRP2, and MRP3, but inhibited the expression of CYP2E1, SULT1A1, and SULT1A3.

CONCLUSIONS

HQ and its main bioactive compounds, including AS-IV, CS, and FMNT significantly regulated the expression of the major DMEs and ETs. HQ produced stronger regulations (induction or inhibition) on DMEs and ETs than AS-IV, CS, or FMNT alone. The results indicate that potential drug-drug interactions might exist when the tested drugs, specifically HQ, are co-administered with other substrate drugs that are metabolized or transported via the studied DMEs or ETs. This study provides beneficial information for appropriate use of HQ for clinical therapy.

The Effect of Vinpocetine on Human Cytochrome P450 Isoenzymes by Using a Cocktail Method

Vinpocetine is a derivative of the alkaloid vincamine, which had been prescribed for chronic cerebral vascular ischemia and acute ischemic stroke or used as a dietary supplement for its several different mechanisms of biological activities. However, information on the cytochrome P450 (CYP) enzyme-mediated drug metabolism has not been previously studied. The present study was performed to investigate the effects of vinpocetine on CYPs activity, and cocktail method was used, respectively. To evaluate the effects of vinpocetine on the activity of human CYP3A4, CYP2C9, CYP2C19, CYP2D6, and CYP2E1, human liver microsomes were utilized to incubate with the mixed CYPs probe substrates and the target components. The results indicate that vinpocetine exhibited weak inhibitory effect on the CYP2C9, where the IC₅₀ value is 68.96 μM, whereas the IC₅₀ values for CYP3A4, CYP2C19, CYP2D6, and CYP2E1 were all over range of 100 μM, which showed that vinpocetine had no apparent inhibitory effects on these CYPs. In conclusion, the results indicated that drugs metabolized by CYP2C9 coadministrated with vinpocetine may require attention or dose adjustment.

An ex vivo approach to botanical-drug interactions: a proof of concept study

ETHNOPHARMACOLOGICAL RELEVANCE

Botanical medicines are frequently used in combination with therapeutic drugs, imposing a risk for harmful botanical-drug interactions (BDIs). Among the existing BDI evaluation methods, clinical studies are the most desirable, but due to their expense and protracted time-line for completion, conventional in vitro methodologies remain the most frequently used BDI assessment tools. However, many predictions generated from in vitro studies are inconsistent with clinical findings. Accordingly, the present study aimed to develop a novel ex vivo approach for BDI assessment and expand the safety evaluation methodology in applied ethnopharmacological research.

MATERIALS AND METHODS

This approach differs from conventional in vitro methods in that rather than botanical extracts or individual phytochemicals being prepared in artificial buffers, human plasma/serum collected from a limited number of subjects administered botanical supplements was utilized to assess BDIs. To validate the methodology, human plasma/serum samples collected from healthy subjects administered either milk thistle or goldenseal extracts were utilized in incubation studies to determine their potential inhibitory effects on CYP2C9 and CYP3A4/5, respectively. Silybin A and B, two principal milk thistle phytochemicals, and hydrastine and berberine, the purported active constituents in goldenseal, were evaluated in both phosphate buffer and human plasma based in vitro incubation systems.

RESULTS

Ex vivo study results were consistent with formal clinical study findings for the effect of milk thistle on the disposition of tolbutamide, a CYP2C9 substrate, and for goldenseal׳s influence on the pharmacokinetics of midazolam, a widely accepted CYP3A4/5 substrate. Compared to conventional in vitro BDI methodologies of assessment, the introduction of human plasma into the in vitro study model changed the observed inhibitory effect of silybin A, silybin B and hydrastine and berberine on CYP2C9 and CYP3A4/5, respectively, results which more closely mirrored those generated in clinical study.

CONCLUSIONS

Data from conventional buffer-based in vitro studies were less predictive than the ex vivo assessments. Thus, this novel ex vivo approach may be more effective at predicting clinically relevant BDIs than conventional in vitro methods.

Pharmacokinetic interactions of herbs with cytochrome p450 and p-glycoprotein

The concurrent use of drugs and herbal products is becoming increasingly prevalent over the last decade. Several herbal products have been known to modulate cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp) which are recognized as representative drug metabolizing enzymes and drug transporter, respectively. Thus, a summary of knowledge on the modulation of CYP and P-gp by commonly used herbs can provide robust fundamentals for optimizing CYP and/or P-gp substrate drug-based therapy. Herein, we review ten popular medicinal and/or dietary herbs as perpetrators of CYP- and P-gp-mediated pharmacokinetic herb-drug interactions. The main focus is placed on previous works on the ability of herbal extracts and their phytochemicals to modulate the expression and function of CYP and P-gp in several in vitro and in vivo animal and human systems.

The effects of milk thistle (Silybum marianum) on human cytochrome P450 activity

Milk thistle (Silybum marianum) extracts are widely used as a complementary and alternative treatment of various hepatic conditions and a host of other diseases/disorders. The active constituents of milk thistle supplements are believed to be the flavonolignans contained within the extracts. In vitro studies have suggested that some milk thistle components may significantly inhibit specific cytochrome P450 (P450) enzymes. However, determining the potential for clinically significant drug interactions with milk thistle products has been complicated by inconsistencies between in vitro and in vivo study results. The aim of the present study was to determine the effect of a standardized milk thistle supplement on major P450 drug-metabolizing enzymes after a 14-day exposure period. CYP1A2, CYP2C9, CYP2D6, and CYP3A4/5 activities were measured by simultaneously administering the four probe drugs, caffeine, tolbutamide, dextromethorphan, and midazolam, to nine healthy volunteers before and after exposure to a standardized milk thistle extract given thrice daily for 14 days. The three most abundant falvonolignans found in plasma, following exposure to milk thistle extracts, were silybin A, silybin B, and isosilybin B. The concentrations of these three major constituents were individually measured in study subjects as potential perpetrators. The peak concentrations and areas under the time-concentration curves of the four probe drugs were determined with the milk thistle administration. Exposure to milk thistle extract produced no significant influence on CYP1A2, CYP2C9, CYP2D6, or CYP3A4/5 activities.

Evaluation of the transporter-mediated herb-drug interaction potential of DA-9801, a standardized dioscorea extract for diabetic neuropathy, in human in vitro and rat in vivo

Background

Drug transporters play important roles in the absorption, distribution, and elimination of drugs and thereby, modulate drug efficacy and toxicity. With a growing use of poly pharmacy, concurrent administration of herbal extracts that modulate transporter activities with drugs can cause serious adverse reactions. Therefore, prediction and evaluation of drug-drug interaction potential is important in the clinic and in the drug development process. DA-9801, comprising a mixed extract of Dioscoreae rhizoma and Dioscorea nipponica Makino, is a new standardized extract currently being evaluated for diabetic peripheral neuropathy in a phase II clinical study.

Method

The inhibitory effects of DA-9801 on the transport functions of organic cation transporter (OCT)1, OCT2, organic anion transporter (OAT)1, OAT3, organic anion transporting polypeptide (OATP)1B1, OATP1B3, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP) were investigated in HEK293 or LLC-PK1 cells. The effects of DA-9801 on the pharmacokinetics of relevant substrate drugs of these transporters were also examined in vivo in rats.

Results

DA-9801 inhibited the in vitro transport activities of OCT1, OCT2, OAT3, and OATP1B1, with IC₅₀ values of 106, 174, 48.1, and 273 μg/mL, respectively, while the other transporters were not inhibited by 300 μg/mL DA-9801. To investigate whether this inhibitory effect of DA-9801 on OCT1, OCT2, and OAT3 could change the pharmacokinetics of their substrates in vivo, we measured the pharmacokinetics of cimetidine, a substrate for OCT1, OCT2, and OAT3, and of furosemide, a substrate for OAT1 and OAT3, by co-administration of DA-9801 at a single oral dose of 1,000 mg/kg. Pre-dose of DA-9801 5 min or 2 h prior to cimetidine administration decreased the C_max of cimetidine in rats. However, DA-9801 did not affect the elimination parameters such as half-life, clearance, or amount excreted in the urine, suggesting that it did not inhibit elimination process of cimetidine, which is governed by OCT1, OCT2, and OAT3. Moreover, DA-9801 did not affect the pharmacokinetic characteristics of furosemide, as evidenced by its unchanged pharmacokinetic parameters.

Conclusion

Inhibitory effects of DA-9801 on OCT1, OCT2, and OAT3 observed in vitro may not necessarily translate into in vivo herb-drug interactions in rats even at its maximum effective dose.

Case report: boldo (Peumus boldus) and tacrolimus interaction in a renal transplant patient

INTRODUCTION

Boldo is an extract of a Chilean tree leave (Peumus boldus mol) that have been traditionally employed in folk medicine. We have presented a case of subtherapeutic tacrolimus levels in a renal transplant patient while taking boldo. In the literature search, no interaction has been reported between boldo and tacrolimus.

CASE REPORT

A 78-year-old Hispanic man with history of diabetes mellitus, hypertension, and deceased donor renal transplant in 2005 presented to the renal clinic for regular follow-up on September 1, 2010. No complaints were reported and physical examination was unremarkable. Laboratory tests taken on July 26, 2010, were significant for tacrolimus level of <3 ng/mL (measured by liquid chromatography/tandem mass spectrometry) and serum creatinine of 1.2 mg/dL (106 μmol/L). Medications included tacrolimus 2 mg bid and mycophenolate 500 mg bid. On further inquiry, the patient admitted taking herbal medication, boldo 300 mg bid, for the last few weeks. There was no change in his regular medications. He was adherent to his medication. He had been taking tacrolimus from the same company and pharmacy since August 2009. The last dose of boldo was on September 1, 2010. One week after he stopped taking boldo, tacrolimus level was 6.1 ng/mL (9/8/2010) on the same tacrolimus dose of 2 mg bid. Tacrolimus dose was increased to 3 mg bid (9/9/2010), awaiting tacrolimus levels. Subsequent levels (ng/mL) were 8.6 and 9.5, which made us resume the prior tacrolimus dose (2 mg bid).

CONCLUSIONS

We have reported a case of an allograft renal transplant recipient who presented to the clinic with subtherapeutic levels of tacrolimus while taking the herbal remedy boldo. Tacrolimus levels rose to the intended target after discontinuation of boldo. Although it is a single case report, our observation suggests a possible herb-drug interaction.