Enhanced Oral Bioavailability of Diltiazem by the Influence of Gallic Acid and Ellagic Acid in Male Wistar Rats: Involvement of CYP3A and P-gp Inhibition

Strategy to Improve the Oral Pharmacokinetics of Cyclin-Dependent Kinase 4/6 Inhibitors: Enhancing Permeability and CYP450 Inhibition by a Natural Bioenhancer

Palbociclib and ribociclib an orally bioavailable, potent cyclin-dependent kinase 4/6 inhibitors, with low oral bioavailability due to substrate specificity towards CYP3A and P-glycoprotein. Thus, current research aims to examine the effect of a bioenhancer (naringin), on oral pharmacokinetics of palbociclib and ribociclib. Naringin's affinity for CYP3A4 and P-glycoprotein was studied using molecular docking; its impact on palbociclib/ribociclib CYP3A metabolism and P-glycoprotein-mediated efflux was examined using in vitro preclinical models; and its oral pharmacokinetics in rats were assessed following oral administration of palbociclib/ribociclib in presence of naringin (50 and 100 mg/kg). Naringin binds optimally to both proteins with the highest net binding energy of - 1477.23 and - 1607.47 kcal/mol, respectively. The microsomal intrinsic clearance of palbociclib and ribociclib was noticeably reduced by naringin (5-100 µM), by 3.0 and 2.46-folds, respectively. Similarly, naringin had considerable impact on the intestinal transport and efflux of both drugs. The pre-treatment with 100 mg/kg naringin increased significantly (p < 0.05) the oral exposure of palbociclib (2.0-fold) and ribociclib (1.95-fold). Naringin's concurrent administration of palbociclib and ribociclib increased their oral bioavailability due to its dual inhibitory effect on CYP3A4 and P-glycoprotein; thus, concurrent naringin administration may represent an innovative strategy for enhancing bioavailability of cyclin-dependent kinase inhibitors.

Effect of co-administration of gallic acid and quercetin or gallic acid and rutin on impaired spermatogenesis and oxidative damage in a busulfan-treated rat model

Gallic acid (GAL), rutin (RUT), and quercetin (QUE) are common antioxidant agents in fruits and vegetables with intriguing pharmacological effects. In the present study, we compared the therapeutic outcomes of GAL + QUE in comparison with GAL + RUT co-treatment in a busulfan (BUS) model of testicular injury in Wistar rats. BUS (4 mg kg-1 body weight (b.w) was injected intraperitoneally daily for 4 days. GAL + RUT or GAL + QUE (20 mg kg-1 b. w) was delivered by oral gavage for 52 days. Examination of the testes of BUS-treated rats both biochemically and under light microscopy revealed an increased level of lipid peroxidation, DNA fragmentation, glutathione-S-transferase, lactate dehydrogenase, gamma-glutamyl transpeptidase, alkaline phosphatase and acid phosphatase with a concomitant decrease in the level of antioxidants: glutathione, ascorbic acid, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, suggesting testicular injury. Tissue sections confirmed the testicular injury-induced by BUS, including diminished spermatogenesis score index, tubular diameter, gonado-somatic index, testis weight, epithelia thickness and higher percentage of aberrant tubules. GAL + QUE co-administration had better recovery effects than GAL + RUT on the biochemical markers and protected against BUS-induced testicular damage. GAL + QUE treatment regimen has better capacity to maintain the antioxidant capacity of the testes and is more potent at reducing BUS-induced oxidative damage compared to GAL + RUT.

Dietary gallic acid as an antioxidant: A review of its food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions

Gallic acid (GA), a dietary phenolic acid with potent antioxidant activity, is widely distributed in edible plants. GA has been applied in the food industry as an antimicrobial agent, food fresh-keeping agent, oil stabilizer, active food wrap material, and food processing stabilizer. GA is a potential dietary supplement due to its health benefits on various functional disorders associated with oxidative stress, including renal, neurological, hepatic, pulmonary, reproductive, and cardiovascular diseases. GA is rapidly absorbed and metabolized after oral administration, resulting in low bioavailability, which is susceptible to various factors, such as intestinal microbiota, transporters, and metabolism of galloyl derivatives. GA exhibits a tendency to distribute primarily to the kidney, liver, heart, and brain. A total of 37 metabolites of GA has been identified, and decarboxylation and dihydroxylation in phase I metabolism and sulfation, glucuronidation, and methylation in phase Ⅱ metabolism are considered the main in vivo biotransformation pathways of GA. Different types of nanocarriers, such as polymeric nanoparticles, dendrimers, and nanodots, have been successfully developed to enhance the health-promoting function of GA by increasing bioavailability. GA may induce drug interactions with conventional drugs, such as hydroxyurea, linagliptin, and diltiazem, due to its inhibitory effects on metabolic enzymes, including cytochrome P450 3A4 and 2D6, and transporters, including P-glycoprotein, breast cancer resistance protein, and organic anion-transporting polypeptide 1B3. In conclusion, in-depth studies of GA on food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions have laid the foundation for its comprehensive application as a food additive and dietary supplement.

The Use of an Antioxidant Enables Accurate Evaluation of the Interaction of Curcumin on Organic Anion-Transporting Polypeptides 4C1 by Preventing Auto-Oxidation

Flavonoids have garnered attention because of their beneficial bioactivities. However, some flavonoids reportedly interact with drugs via transporters and may induce adverse drug reactions. This study investigated the effects of food ingredients on organic anion-transporting polypeptide (OATP) 4C1, which handles uremic toxins and some drugs, to understand the safety profile of food ingredients in renal drug excretion. Twenty-eight food ingredients, including flavonoids, were screened. We used ascorbic acid (AA) to prevent curcumin oxidative degradation in our method. Twelve compounds, including apigenin, daidzein, fisetin, genistein, isorhamnetin, kaempferol, luteolin, morin, quercetin, curcumin, resveratrol, and ellagic acid, altered OATP4C1-mediated transport. Kaempferol and curcumin strongly inhibited OATP4C1, and the Ki values of kaempferol (AA(-)), curcumin (AA(-)), and curcumin (AA(+)) were 25.1, 52.2, and 23.5 µM, respectively. The kinetic analysis revealed that these compounds affected OATP4C1 transport in a competitive manner. Antioxidant supplementation was determined to benefit transporter interaction studies investigating the effects of curcumin because the concentration-dependent curve evidently shifted in the presence of AA. In this study, we elucidated the food-drug interaction via OATP4C1 and indicated the utility of antioxidant usage. Our findings will provide essential information regarding food-drug interactions for both clinical practice and the commercial development of supplements.

A review of recent progress in improving the bioavailability of nutraceutical-loaded emulsions after oral intake

Increasing awareness of the health benefits of specific constituents in fruits, vegetables, cereals, and other whole foods has sparked a broader interest in the potential health benefits of nutraceuticals. Many nutraceuticals are hydrophobic substances, which means they must be encapsulated in colloidal delivery systems. Oil-in-water emulsions are one of the most widely used delivery systems for improving the bioavailability and bioactivity of these nutraceuticals. The composition and structure of emulsions can be designed to improve the water dispersibility, physicochemical stability, and bioavailability of the encapsulated nutraceuticals. The nature of the emulsion used influences the interfacial area and properties of the nutraceutical-loaded oil droplets in the gastrointestinal tract, which influences their digestion, as well as the bioaccessibility, metabolism, and absorption of the nutraceuticals. In this article, we review recent in vitro and in vivo studies on the utilization of emulsions to improve the bioavailability of nutraceuticals. The findings from this review should facilitate the design of more efficacious nutraceutical-loaded emulsions with increased bioactivity.

Inhibitory effects of Triphala on CYP isoforms in vitro and its pharmacokinetic interactions with phenacetin and midazolam in rats

Context

Direct evidence of Triphala-drug interactions has not been provided to date.

Objective

This study was aimed to determine the effects of Triphala on cytochrome P450 (CYP) isoforms and P-glycoprotein (P-gp) in vitro, and to investigate pharmacokinetic interactions of Triphala with CYP-probes in rats.

Materials and methods

Effects of Triphala on the activities of CYP isoforms and P-gp were examined using human liver microsomes (HLMs) and Caco-2 cells, respectively. Pharmacokinetic interactions between Triphala and CYP-probes (i.e., phenacetin and midazolam) were further examined in rats.

Results

Triphala extract inhibited the activities of CYP isoforms in the order of CYP1A2>3A4>2C9>2D6 with the IC₅₀ values of 23.6 ± 9.2, 28.1 ± 9.8, 30.41 ± 16.7 and 93.9 ± 27.5 μg/mL, respectively in HLMs. It exhibited a non-competitive inhibition of CYP1A2 and 2C9 with the K_i values of 23.6 and 30.4 μg/mL, respectively, while its inhibition on CYP3A4 was competitive manner with the Ki values of 64.9 μg/mL. The inhibitory effects of Triphala on CYP1A2 and 3A4 were not time-dependent. Moreover, Triphala did not affect the P-gp activity in Caco-2 cells. Triphala, after its oral co-administration at 500 mg/kg, increased the bioavailabilities of phenacetin and midazolam by about 61.2% and 40.7%, respectively, in rats.

Discussion and conclusions

Increases observed in the bioavailabilities of phenacetin and midazolam after oral co-administration of Triphala in rats provided a direct line of evidence to show Triphala-drug interactions via inhibition of CYP1A and CYP3A activities, respectively. These results, together with the lack of time-dependency of CYP 1A2 and 3A4 inhibition in vitro, suggested that the inhibitory effect of Triphala is primarily reversible.

Intestinal metabolism and absorption mechanism of multi-components in Gaultheria leucocarpa var. yunnanensis - An assessment using in situ and in vitro models, comparing gut segments in pathological with physiological conditions

ETHNOPHARMACOLOGICAL RELEVANCE

Dianbaizhu (Gaultheria leucocarpa var. yunnanensis) as a Chinese folk medicine exerts significant treatment effects on rheumatoid arthritis (RA) with a long historical time. Our previous reports showed that the anti-rheumatic arthritis fraction (ARF) extracted and enriched from Dianbaizhu possessed good druggability, which was better than its single active ingredients. However, the intestinal transport characteristics and mechanism of ARF have not been elucidated to date.

AIM OF THE STUDY

In order to illustrate the role of active ingredients of ARF in alleviating RA and promoting the development of dosage forms, the intestinal metabolism, absorption properties and mechanism of ARF in vitro and in situ models were investigated.

MATERIALS AND METHODS

Firstly, after incubating with 4 intestinal segments (duodenum, jejunum, ileum, and colon), 7 key components in ARF, including MATG-B, (+)-catechin, MSTG-A, Gaultherin, chlorogenic acid, quercetin, and kaempferol were quantitatively analyzed by a high-performance liquid chromatography (HPLC). Secondly, combining the physiological and pathological rats, the in situ single-pass intestinal perfusion and in vitro everted gut sacs of rats were performed to investigate the absorption features and transport mechanisms of ARF using HPLC and HPLC-Q-TOF-MS/MS. Subsequently, in situ studies were employed to determine the effect of P-glycoprotein (P-gp) inhibitor (verapamil) on the transport characteristics of ARF in RA model rats.

RESULTS

Comparing the absorption parameters of ARF incubated in different intestinal segments, data showed that the absorption of ARF in the small intestine was significantly stronger than that of the colon (P < 0.01). The number of characterized prototype components was subjected to the incubation time, drug concentration and rat body condition, but not the intestinal segments. There were no significant differences in the number of metabolites among different intestinal segments, administration concentrations and incubation time. The best small intestinal absorption site of ARF was duodenum and ileum in normal and model rats, respectively. The P_eff values of 7 index compounds were all higher than 0.2 × 10^-4cm/s, and the F_a values of 7 index compounds were all greater than 20% in the in situ perfusion investigation. The results showed that MSTG-B, MSTG-A and Gaultherin were likely to be substrates of P-gp as verapamil significantly enhanced their P_eff and K_a values, while other ingredients were not P-gp substrates.

CONCLUSIONS

The intestinal membrane permeability of ARF was good. Its intestinal absorption mechanisms mainly involved active transportation processes and passive diffusion. Besides, this report provided data support and basis for clinical development, bioavailability improvement and formulation design.

Gallic acid for cancer therapy: Molecular mechanisms and boosting efficacy by nanoscopical delivery

Cancer is the second leading cause of death worldwide. Majority of recent research efforts in the field aim to address why cancer resistance to therapy develops and how to overcome or prevent it. In line with this, novel anti-cancer compounds are desperately needed for chemoresistant cancer cells. Phytochemicals, in view of their pharmacological activities and capacity to target various molecular pathways, are of great interest in the development of therapeutics against cancer. Plant-derived-natural products have poor bioavailability which restricts their anti-tumor activity. Gallic acid (GA) is a phenolic acid exclusively found in natural sources such as gallnut, sumac, tea leaves, and oak bark. In this review, we report on the most recent research related to anti-tumor activities of GA in various cancers with a focus on its underlying molecular mechanisms and cellular pathwaysthat that lead to apoptosis and migration of cancer cells. GA down-regulates the expression of molecular pathways involved in cancer progression such as PI3K/Akt. The co-administration of GA with chemotherapeutic agents shows improvements in suppressing cancer malignancy. Various nano-vehicles such as organic- and inorganic nano-materials have been developed for targeted delivery of GA at the tumor site. Here, we suggest that nano-vehicles improve GA bioavailability and its ability for tumor suppression.

Molecular dynamic mechanism(s) of inhibition of bioactive antiviral phytochemical compounds targeting cytochrome P450 3A4 and P-glycoprotein

P-glycoprotein (ABCB1) and cytochrome P450 3A4 (CYP3A4) metabolize almost all known human immunodeficiency virus' protease inhibitor drugs (PIs). Over induction of these proteins' activities has been linked to rapid metabolism of PIs which are then pumped out of the circulatory system, eventually leading to drug-resistance in HIV-positive patients. This study aims to determine, with the use of computational tools, the inhibitory potential of four phytochemical compounds (PCs) (epigallocatechin gallate (EGCG), kaempferol-7-glucoside (K7G), luteolin (LUT) and ellagic acid (EGA)) in inhibiting the activities of these drug-metabolizing proteins. The comparative analysis of the MM/GBSA results revealed that the binding affinity (ΔG_bind) of EGCG and K7G for CYP3A4 and ABCB1 are higher than LUT and EGA and fall between the ΔG_bind of the inhibitors of CYP3A4 and ABCB1 (Ritonavir (strong inhibitor) and Lopinavir (moderate inhibitor)). The structural analysis (RMSD, RMSF, RoG and protein-ligand interaction plots) also confirmed that EGCG and K7G showed similar inhibitory activities with the inhibitors. The study has shown that EGCG and K7G have inhibitory activities against the two proteins and assumes they could decrease intracellular efflux of PIs, consequently increasing the optimal concentration of PIs in the systemic circulation.Communicated by Ramaswamy H. Sarma.

Evaluation of the Role of P-glycoprotein (P-gp)-Mediated Efflux in the Intestinal Absorption of Common Substrates with Elacridar, a P-gp Inhibitor, in Rats

BACKGROUND AND OBJECTIVES

P-glycoprotein (P-gp) has been shown previously to contribute to the intestinal absorption of verapamil, diltiazem, tacrolimus, colchicine and indinavir in situ; however, its contribution in vivo is unknown. The present study aimed to evaluate the in vivo involvement of P-gp using elacridar as its inhibitor to distinguish the contribution of P-gp from cytochrome P450 (CYP) 3A.

METHODS

Fexofenadine (5 mg/kg) and buspirone (1 mg/kg) were used as probe substrates of P-gp and CYP3A, respectively. Each dual substrate (1 or 2 mg/kg) was orally administered to rats after elacridar pre-treatment (3 mg/kg). Additionally, verapamil, diltiazem or tacrolimus was orally co-administered with fexofenadine.

RESULTS

Elacridar drastically increased the area under the plasma concentration-time curve (AUC_0-t) of oral fexofenadine by 8.6-fold; however, it did not affect the AUC_0-t of oral buspirone. Therefore, elacridar inhibited P-gp without affecting CYP3A. The absorption of oral verapamil, diltiazem and tacrolimus was not influenced by elacridar pre-treatment, and the increase in the AUC_0-t of fexofenadine was approximately 3-fold when co-administered with each substrate; the minimal effect of elacridar was attributable to the limited contribution of P-gp but not to their self-inhibition against the transporter. Conversely, elacridar significantly increased the AUC_0-t of colchicine (5.3-fold) and indinavir (2.0-fold), indicating that P-gp contributes to their absorption.

CONCLUSIONS

Elacridar is useful for distinguishing the contribution of P-gp from CYP3A to the absorption of drugs in rats. The in vivo contribution of P-gp is minimal for high permeable compounds owing to their fraction absorbed of nearly 1.0.

Food-Drug Interaction between the Adlay Bran Oil and Drugs in Rats

Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) contains various phytonutrients for treating many diseases in Asia. To investigate whether orally administered adlay bran oil (ABO) can cause drug interactions, the effects of ABO on the pharmacokinetics of five cytochrome P450 (CYP) probe drugs were evaluated. Rats were given a single oral dose (2.5 mL/kg BW) of ABO 1 h before administration of a drug cocktail either orally or intravenously, and blood was collected at various time points. A single oral dose of ABO administration did not affect the pharmacokinetics of five probe drugs when given as a drug cocktail intravenously. However, ABO increased plasma theophylline (+28.4%), dextromethorphan (+48.7%), and diltiazem (+46.7%) when co-administered an oral drug cocktail. After 7 days of feeding with an ABO-containing diet, plasma concentrations of theophylline (+45.4%) and chlorzoxazone (+53.6%) were increased after the oral administration of the drug cocktail. The major CYP enzyme activities in the liver and intestinal tract were not affected by ABO treatment. Results from this study indicate that a single oral dose or short-term administration of ABO may increase plasma drug concentrations when ABO is given concomitantly with drugs. ABO is likely to enhance intestinal drug absorption. Therefore, caution is needed to avoid food–drug interactions between ABO and co-administered drugs.

Optimization of the traditional processing method for precision detoxification of CaoWu through biomimetic linking kinetics and human toxicokinetics of aconitine as toxic target marker

ETHNOPHARMACOLOGICAL RELEVANCE

CaoWu (Aconiti Kusnezoffii Radix), well known for its high toxicity leading to fatal ventricular arrhythmias, is detoxified by HeZi (Terminalia Chebula Retz) decoction to prepare ZhiCaoWu (Aconiti Kusnezoffii Radix Preparata) as one part of ingredients of NaRu-3 pill which is used for the treatment of rheumatoid arthritis (RA). Aconitine (AC) is a highly toxic alkaloid of CaoWu and it is used as toxic target marker for the quality control (QC) of ZhiCaoWu. In the traditional processing method, the vanish of astringent or spicy feeling in tongue is the important detoxification indicator of ZhiCaoWu. However, how CaoWu is detoxified to ZhiCaoWu and whether the appropriate content of AC in ZhiCaoWu can be efficiently perceived after the empirical detoxification still lack factual basis.

AIM OF THE STUDY

The present study aimed to optimize the traditional processing method for precision detoxification of CaoWu through biomimetic linking kinetics and human toxicokinetics (TK) of AC, with a view of providing insights into the changes of toxic target marker.

MATERIALS AND METHODS

CaoWu medicinal slices (Mes) and coarse powder (Cop) were processed by blank HeZi decoction through the soaking method for 7 days. High-performance liquid chromatography (HPLC) was used for the analysis of the samples. The acidity of blank HeZi decoction and HeZi processing decoction was directly determined by pH meter. The non-compartment analysis (NCA) was used to have an intuitive appreciation for AC and pH changes in HeZi processing decoction while the compartment model method was used to build the biomimetic linking kinetics model with the covariate. The inter-species scaling of animal TK parameters was conducted to predict human AC TK profiles. The possible uptake ways of AC (rapid-release or extended-release) for humans were attempted to assess the poisoning risk of AC in NaRu-3 pill. Based on the target content of AC in ZhiCaoWu, the biomimetic linking kinetics model was explored to optimize the traditional processing detoxification method of CaoWu. The assays of determining inflammatory cytokines in lipopolysaccharides (LPS)-induced RAW264.7 cells were performed to investigate the inflammatory modulation effects of AC in vitro.

RESULTS

ZhiCaoWu was prepared by eliminating redundant AC in CaoWu through the repeatable replacement of HeZi processing decoction in which its acidity (pH) was affected. AC-pH changes in HeZi processing decoction were adequately depicted by a biomimetic linking kinetics model whose predictive power was determined by comparing the predictions of AC in ZhiCaoWu with the reported data. Rapid-release AC at the converted dose of 111.1 and 417.6 μg (0.011 and 0.042% of AC in NaRu-3 pill) reached maximum blood concentrations of 26.1 and 98.1 ng/mL at 0.3 h, in comparison with minimum human lethal concentration (100 ng/mL). Achieving the target content of AC (0.04%) in ZhiCaoWu or AC (0.011%) in NaRu-3 pill to precisely control the poisoning risk, the potential optimized protocols were that the processing time at 0.2-0.8% of AC in CaoWu was 2.0-4.4 days for Cop and 2.7-6.2 days for Mes. Correspondingly, pH values in HeZi processing decoction were 3.95 and 3.77 for Cop and Mes, respectively. Meanwhile, Lipopolysaccharides (LPS)-induced RAW264.7 cells were exposed to 0, 20, and 200 μM of AC for 12 h and AC at 20 μM enhanced the levels of IL-6, IL-10 and TNF-α.

CONCLUSIONS

Thus, for the first time, a biomimetic linking kinetics model was built to optimize the traditional detoxification method. Moreover, pH changes could be developed as surrogate endpoint for guiding the processing detoxification of CaoWu. Notably, setting the content limit of AC (0.011%) was very rational to control the poisoning risk of NaRu-3 pill. In addition, it was possible that there existed the more complex mechanisms of AC for inflammatory modulation in vitro.

Enhanced oral bioavailability of linagliptin by the influence of gallic acid and ellagic acid in male Wistar albino rats: involvement of p-glycoprotein inhibition

Background Linagliptin is an antidiabetic drug used for the treatment of type-2 diabetes. The oral bioavailability of linagliptin is low (29.5%) due to its first pass metabolism in the intestine and liver. Gallic acid and ellagic acid are natural polyphenols which are widely distributed in fruits and medicinal plants. Gallic acid and ellagic acid have been reported to inhibit p-glycoprotein (p-gp) and enhance the bioavailability of p-gp substrate drugs. Hence, the purpose of the study was to evaluate the effect of gallic acid and ellagic acid on intestinal transport and bioavailability of linagliptin, a p-gp substrate in diabetic rats. Methods The intestinal transport of linagliptin was assessed by conducting an in situ single-pass intestinal perfusion study. The oral pharmacokinetics was evaluated by conducting oral bioavailability study in diabetic rats. Results After pretreatment with gallic acid and ellagic acid, no significant change in effective permeability of linagliptin was observed at the ileum part of the rat intestine. A significant improvement in the peak serum concentration (Cmax) and area under the serum concentration time profile (AUC), AUMC, AUCtotal and decrease in clearance were observed in rats pretreated with gallic acid and ellagic acid. Conclusions This study demonstrates that gallic acid and ellagic acids increase the bioavailability of oral linagliptin in rats due to the inhibition of p-gp. These animal data need to be confirmed in a clinical setting to determine whether linagliptin dosing should be adjusted when given concomitantly with these phytochemicals or gallic acid/ellagic acid-containing dietary supplements.

[Calcium channel blocker diltizem transiently inhibits migration and up-regulates metadherin expression in hepatocellular carcinoma cells in vitro]

OBJECTIVE

To investigate the effect of calcium channel blocker diltizem in reversing multi-drug resistance (MDR) and on metadherin expression in hepatocellular carcinoma cells and explore the molecular mechanism.

METHODS

Hepatocellular carcinoma MHCC97H and 7402 cells were treated with diltiazem hydrochloride, a calcium channel blocker (0, 25, 50, 100, 200, and 400 μmol/L), for 12, 24, or 48 h. Wound healing assay was employed to assess the changes in the mobility and migration of the cells following the treatments, and the changes in the expression levels of metadherin mRNA and protein and P-gp protein were determined using RT-PCR and immunocytochemistry.

RESULTS

Diltiazem hydrochloride could transiently inhibit the migration and movement of MHCC97H and 7402 cells in vitro in a time-and concentration-dependent manner (P < 0.05). Diltiazem hydrochloride at different concentrations also transiently up-regulated the expressions of metadherin mRNA and protein but did not inhibit the expression of P-gp protein in MHCC97H and 7402 cells.

CONCLUSIONS

Calcium channel blocker can transiently inhibit the migration of hepatocellular carcinoma cells in vitro and up-regulate the expression of metadherin mRNA and protein through a feedback mechanism, suggesting the potential risk of calcium channel blockers for promoting tumor progression during the treatment of malignant tumors.

Critical pharmacokinetic and pharmacodynamic drug-herb interactions in rats between warfarin and pomegranate peel or guava leaves extracts

BACKGROUND

In-depth information of potential drug-herb interactions between warfarin and herbal compounds with suspected anticoagulant blood thinning effects is needed to raise caution of concomitant administration. The current study aimed to investigate the impact of co-administration of pomegranate peel and guava leaves extracts, including their quality markers namely; ellagic acid and quercetin, respectively, on warfarin's in vivo dynamic activity and pharmacokinetic actions, in addition to potential in vitro cytochrome P450 enzymes (CYP) inhibition.

METHODS

Influence of mentioned extracts and their key constituents on warfarin pharmacodynamic and kinetic actions and CYP activity were evaluated. The pharmacodynamic interactions were studied in Sprague Dawley rats through prothrombin time (PT) and International Normalized Ratio (INR) measurements, while pharmacokinetic interactions were detected in vivo using a validated HPLC method. Furthermore, potential involvement in CYP inhibition was also investigated in vitro on isolated primary rat hepatocytes.

RESULTS

Preparations of pomegranate peel guava leaf extract, ellagic acid and quercetin in combination with warfarin were found to exert further significant increase on PT and INR values (p < 0.01) than when used alone (p < 0.05). Pomegranate peel extract showed insignificant effects on warfarin pharmacokinetics (p > 0.05), however, its constituent, namely, ellagic acid significantly increased warfarin Cmax (p < 0.05). Guava leaves extract and quercetin resulted in significant increase in warfarin Cmax when compared to control (p < 0.01). Furthermore, guava leaves extract showed a significant effect on changing the AUC, CL and Vz. Significant reduction in CYP2C8, 2C9, and 3A4 was seen upon concomitant use of warfarin with ellagic acid, guava leaves and quercetin, unlike pomegranate that insignificantly affected CYP activities.

CONCLUSION

All combinations enhanced the anticoagulant activity of warfarin as the results of in vivo and in vitro studies were consistent. The current investigation confirmed serious drug herb interactions between warfarin and pomegranate peel or guava leaf extracts. Such results might conclude a high risk of bleeding from the co-administration of the investigated herbal drugs with warfarin therapy. In addition, the results raise attention to the blood-thinning effects of pomegranate peel and guava leaves when used alone.

Drug Bioavailability Enhancing Agents of Natural Origin (Bioenhancers) that Modulate Drug Membrane Permeation and Pre-Systemic Metabolism

Many new chemical entities are discovered with high therapeutic potential, however, many of these compounds exhibit unfavorable pharmacokinetic properties due to poor solubility and/or poor membrane permeation characteristics. The latter is mainly due to the lipid-like barrier imposed by epithelial mucosal layers, which have to be crossed by drug molecules in order to exert a therapeutic effect. Another barrier is the pre-systemic metabolic degradation of drug molecules, mainly by cytochrome P450 enzymes located in the intestinal enterocytes and liver hepatocytes. Although the nasal, buccal and pulmonary routes of administration avoid the first-pass effect, they are still dependent on absorption of drug molecules across the mucosal surfaces to achieve systemic drug delivery. Bioenhancers (drug absorption enhancers of natural origin) have been identified that can increase the quantity of unchanged drug that appears in the systemic blood circulation by means of modulating membrane permeation and/or pre-systemic metabolism. The aim of this paper is to provide an overview of natural bioenhancers and their main mechanisms of action for the nasal, buccal, pulmonary and oral routes of drug administration. Poorly bioavailable drugs such as large, hydrophilic therapeutics are often administered by injections. Bioenhancers may potentially be used to benefit patients by making systemic delivery of these poorly bioavailable drugs possible via alternative routes of administration (i.e., oral, nasal, buccal or pulmonary routes of administration) and may also reduce dosages of small molecular drugs and thereby reduce treatment costs.

Inflammation and Oxidative Stress in an Obese State and the Protective Effects of Gallic Acid

Metabolic complications in an obese state can be aggravated by an abnormal inflammatory response and enhanced production of reactive oxygen species. Pro-inflammatory response is known to be associated with the formation of toxic reactive oxygen species and subsequent generation of oxidative stress. Indeed, adipocytes from obese individuals display an altered adipokine profile, with upregulated expression and secretion of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin (IL-6). Interestingly, natural compounds, including phenolic enriched foods are increasingly explored for their ameliorative effects against various metabolic diseases. Of interest is gallic acid, a trihydroxybenzoic acid that has progressively demonstrated robust anti-obesity capabilities in various experimental models. In addition to reducing excessive lipid storage in obese subjects, gallic acid has been shown to specifically target the adipose tissue to suppress lipogenesis, improve insulin signaling, and concomitantly combat raised pro-inflammatory response and oxidative stress. This review will revise mechanisms involved in the pathophysiological effects of inflammation and oxidative stress in an obese state. To better inform on its therapeutic potential and improvement of human health, available evidence reporting on the anti-obesity properties of gallic acid and its derivatives will be discussed, with emphases on its modulatory effect on molecular mechanisms involved in insulin signaling, inflammation and oxidative stress.