Effect of piperine on the steady-state pharmacokinetics of phenytoin in patients with epilepsy

Synthesis, characterization, and anti-inflammatory activity of tetrahydropiperine, piperic acid, and tetrahydropiperic acid via down regulation of NF-κB pathway

The present study describes the synthesis, characterization, and evaluation of tetrahydropiperine (THP), piperic acid (PA), and tetrahydropiperic acid (THPA) as anti-inflammatory agents. THPA demonstrated potent anti-inflammatory activity among all the compounds. The anti-inflammatory potential was investigated in both in-vitro and in-vivo experimental models. Our findings demonstrated that THPA effectively suppressed the production of pro-inflammatory mediators, including nitric oxide and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in both in vitro and in vivo. Additionally, THPA attenuated the expression of i-NOS and COX-2 in RAW 264.7 macrophages. The oral administration of THPA significantly reduced carrageenan induced paw edema thickness and alleviated liver, lung, and kidney injury induced by LPS. THPA also reduced the infiltration of inflammatory cells, prevented the occurrence of significant lesions, and mitigated tissue damage. Moreover, THPA significantly improved the survival rate of mice challenged with LPS. Our western blot studies also found that LPS induced NF-κB activation was downregulated by treatment with THPA in an in vivo system. These results collectively illustrated the potential of THPA as a therapeutic agent for treating inflammatory diseases.

Herb-drug interactions: A short review on central and peripheral nervous system drugs

Herbal medicines are widely perceived as natural and safe remedies. However, their concomitant use with prescribed drugs is a common practice, often undertaken without full awareness of the potential risks and frequently without medical supervision. This practice introduces a tangible risk of herb-drug interactions, which can manifest as a spectrum of consequences, ranging from acute, self-limited reactions to unpredictable and potentially lethal scenarios. This review offers a comprehensive overview of herb-drug interactions, with a specific focus on medications targeting the Central and Peripheral Nervous Systems. Our work draws upon a broad range of evidence, encompassing preclinical data, animal studies, and clinical case reports. We delve into the intricate pharmacodynamics and pharmacokinetics underpinning each interaction, elucidating the mechanisms through which these interactions occur. One pressing issue that emerges from this analysis is the need for updated guidelines and sustained pharmacovigilance efforts. The topic of herb-drug interactions often escapes the attention of both consumers and healthcare professionals. To ensure patient safety and informed decision-making, it is imperative that we address this knowledge gap and establish a framework for continued monitoring and education. In conclusion, the use of herbal remedies alongside conventional medications is a practice replete with potential hazards. This review not only underscores the real and significant risks associated with herb-drug interactions but also underscores the necessity for greater awareness, research, and vigilant oversight in this often-overlooked domain of healthcare.

Herb-drug Interactions in Neuropsychiatric Pharmacotherapy - A Review of Clinically Relevant Findings

The management of neuropsychiatric disorders relies heavily on pharmacotherapy. The use of herbal products as complimentary medicine, often concomitantly, is common among patients taking prescription neuropsychiatric drugs. Herb-drug interaction, a clinical consequence of this practice, may jeopardize the success of pharmacotherapy in neuropsychiatry. Besides the wellknown ability of phytochemicals to inhibit and/or induce drug-metabolizing enzymes and transport proteins, several phytoconstituents are capable of exerting pharmacological effects on the central nervous system. This study reviewed the relevant literature and identified 13 commonly used herbal products - celery, echinacea, ginkgo, ginseng, hydroxycut, kava, kratom, moringa, piperine, rhodiola, St. John's wort, terminalia/commiphora ayurvedic mixture and valerian - which have shown clinically relevant interactions with prescription drugs used in the management of neuropsychiatric disorders. The consequent pharmacokinetic and pharmacodynamic interactions with orthodox medications often result in deleterious clinical consequences. This underscores the importance of caution in herb-drug co-medication.

Calcium Ion-Sodium Alginate-Piperine-Based Microspheres: Evidence of Enhanced Encapsulation Efficiency, Bio-Adhesion, Controlled Delivery, and Oral Bioavailability of Isoniazid

Isoniazid (INH) is a first-line chemotherapeutic drug employed in the management of tuberculosis. However, its extensive first-pass metabolism, short-life life, and low oral bioavailability confined its medical application. Therefore, the calcium ion-alginate-piperine microspheres (INH-CaSP Ms) was prepared to enhance encapsulation efficiency, controlled delivery, and oral bioavailability of INH. The INH-CaSP Ms was developed using a modified emulsification method and optimized via Box-Behnken design (BBD). Optimized INH-CaSP Ms were characterized for encapsulation efficiency, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), bio-adhesion, in vitro dissolution, ex vivo permeation, and oral bioavailability studies. Characterization studies confirmed the formation of microspheres. The INH-CaSP Ms showed spherical microspheres with enhanced encapsulation efficiency (~ 93.03 ± 1.54% w/w). The optimized INH-CaSP Ms exhibited higher bio-adhesion around (~ 81.41 ± 1.31%). The INH-CaSP Ms enhanced the dissolution rate of INH (~ 57%) compared to pure INH (~ 57%) and INH-SA Ms (~ 81%) in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.4). The same formulations improved the permeation rate of INH (~ 90%) compared to pure INH (~ 55%) and INH-SA Ms (~ 80%). The oral bioavailability results indicated that INH-CaSP Ms appreciably improved the oral bioavailability of INH via increasing the Cmax, Tmax, t_1/2, and AUC parameters compared to pure INH. The study demonstrates that the development of INH-CaSP Ms via cross-linked coordinate bond interaction between divalent cation calcium ion-alginate complex and anion piperine bio-enhancer is an effective approach for enhancing the encapsulation efficiency, bio-adhesion, controlled release, and oral bioavailability of INH.

PLANT BASED BIOAVAILABILITY ENHANCERS

Many of the synthetic as well as herbal drugs despite of their notable in vitro finding demonstrate insignificant in vivo activity majority of times due to poor bioavailability. As per Biopharmaceutical Classification System (BCS) one of the main concern is low solubility and/or permeation of drugs resulting in reduced absorption and poor bioavailability. To overcome these issues the various strategies have been adopted including use of permeation enhancers which are also known as bioenhancers. Bioenhancers are synthetic or natural compounds that increases the bioavailability of drugs and nutrients such as vitamins, amino acids, minerals, etc. into the systemic circulation and at the site of action for exhibiting improved therapeutic action. By improving bioavailability, bioenhancers can lead to reduction in drug dose, decrease in the treatment period and can circumvent the problem of drug resistance. Numerous studies have reported application of synthetic bioenhancers. On the other hand, owing to the natural origin, plant based bioenhancer can serve as better alternative. Literature review have revealed that the plant-based bioenhancers have been used in with a wide varieties of drugs including antibiotics, antiviral and anti-cancer. These can be categorized based on their sources and the mechanism of activity. This review will provide a systematic and detailed overview of the various plant based bioenhancers and applications.

Therapeutic spectrum of piperine for clinical practice: a scoping review

Translation of traditional knowledge of herbs into a viable product for clinical use is still an uphill task. Piperine, a pungent alkaloid molecule derived from Piper nigrum and Piper longum possesses diverse pharmacological effects. Traditionally, pepper is used for arthritis, bronchitis, gastritis, diarrhea, snake bite, menstrual pain, fever, and bacterial infections, etc. The anti-inflammatory, antioxidant and immunomodulatory actions of piperine are the possible mechanisms behind its therapeutic potential. Various in-silico and experimental studies have shown piperine as a possible promising molecule in coronavirus disease (COVID-19), ebola, and dengue due to its immunomodulatory and antiviral activities. The other important clinical applications of piperine are due to its bio enhancing effect on drugs, by modulating, absorption in the gastrointestinal tract, altering activities of transporters like p-glycoprotein substrates, and modulating drug metabolism by altering the expression of cytochrome P450 or UDP-glucuronosyltransferase enzymes. Piperine attracted clinicians in treating patients with arthritis, metabolic syndrome, diabetes, skin infections, gastric and liver disorders. This review focused on systematic, evidence-based insight into the use of piperine in clinical settings and mechanistic details behind its therapeutic actions. Also, highlights a number of clinical trials of piperine at various stages exploring its clinical application in cancer, neurological, respiratory, and viral disease, etc.

Safety Aspects of the Use of Isolated Piperine Ingested as a Bolus

Piperine is a natural ingredient of Piper nigrum (black pepper) and some other Piper species. Compared to the use of pepper for food seasoning, piperine is used in food supplements in an isolated, concentrated form and ingested as a bolus. The present review focuses on the assessment of the possible critical health effects regarding the use of isolated piperine as a single ingredient in food supplements. In human and animal studies with single or short-term bolus application of isolated piperine, interactions with several drugs, in most cases resulting in increased drug bioavailability, were observed. Depending on the drug and extent of the interaction, such interactions may carry the risk of unintended deleteriously increased or adverse drug effects. Animal studies with higher daily piperine bolus doses than in human interaction studies provide indications of disturbance of spermatogenesis and of maternal reproductive and embryotoxic effects. Although the available human studies rarely reported effects that were regarded as being adverse, their suitability for detailed risk assessment is limited due to an insufficient focus on safety parameters apart from drug interactions, as well as due to the lack of investigation of the potentially adverse effects observed in animal studies and/or combined administration of piperine with other substances. Taken together, it appears advisable to consider the potential health risks related to intake of isolated piperine in bolus form, e.g., when using certain food supplements.

Impacts of Drug Interactions on Pharmacokinetics and the Brain Transporters: A Recent Review of Natural Compound-Drug Interactions in Brain Disorders

Natural compounds such as herbal medicines and/or phyto-compounds from foods, have frequently been used to exert synergistic therapeutic effects with anti-brain disorder drugs, supplement the effects of nutrients, and boost the immune system. However, co-administration of natural compounds with the drugs can cause synergistic toxicity or impeditive drug interactions due to changes in pharmacokinetic properties (e.g., absorption, metabolism, and excretion) and various drug transporters, particularly brain transporters. In this review, natural compound–drug interactions (NDIs), which can occur during the treatment of brain disorders, are emphasized from the perspective of pharmacokinetics and cellular transport. In addition, the challenges emanating from NDIs and recent approaches are discussed.

Awareness and current knowledge of epilepsy

Epilepsy is a severe neural disorder that affects approximately fifty million individuals globally. Despite the fact that for most of the people with epilepsy, convulsions are better controlled by current accessible antiepileptic medicines, yet there are more than 30% of individuals affected with medically intractable epilepsy and around 30-40% of all patients with epilepsy affected by many adverse reactions and convulsion resistance to the present antiepileptic drugs. Consequently, various scientists attempt to develop new strategies to treat epilepsy, for instance, to find out novel antiepileptic ingredients from traditional medicines. This work aims to present a complete summary of natural medicines prescribed as antiepileptic agents all over the world by ethnic groups and different tribes. We undertook an extensive bibliographic analysis by searching peer reviewed papers and classical textbooks and further consulting well accepted worldwide scientific databases. We carried out PubMed, EMbase and CENTRAL searches by means of terms such as "antiepileptic" and "anti-convulsant" activity of plants. Medicinal plants have been prescribed to treat epilepsy and have been recognized as antiepileptic medicines. In this review, a variety of herbs have been reviewed for thorough studies such as Cuminum cyminum, Butea monosperma, Solanum americanum, Anacyclus pyrethrum, Leonotis leonurus, Elaeocarpus ganitrus and Angelica archangelica. This paper shows that it was high time experimental studies are increased to obtain novel potential active principles from medicinal plants. Plant extracts and their chemical constituents should be further evaluated to clarify their mechanisms of action. This paper provides a solid base upon which to further investigate the clinical efficacy of medicinal plants that are both currently prescribed by physicians as traditional antiepileptic agents, but also could be effective as an antiepileptic drug with further research and study.

Piperine-A Major Principle of Black Pepper: A Review of Its Bioactivity and Studies

Piperine is the main compound present in black pepper, and is the carrier of its specific pungent taste, which is responsible for centuries of human dietary utilization and worldwide popularity as a food ingredient. Along with the application as a food ingredient and food preservative, it is used in traditional medicine for many purposes, which has in most cases been justified by modern scientific studies on its biological effects. It has been confirmed that piperine has many bioactive effects, such as antimicrobial action, as well as many physiological effects that can contribute to general human health, including immunomodulatory, hepatoprotective, antioxidant, antimetastatic, antitumor, and many other activities. Clinical studies demonstrated remarkable antioxidant, antitumor, and drug availability-enhancing characteristics of this compound, together with immunomodulatory potential. All these facts point to the therapeutic potential of piperine and the need to incorporate this compound into general health-enhancing medical formulations, as well as into those that would be used as adjunctive therapy in order to enhance the bioavailability of various (chemo)therapeutic drugs.

Insights about multi-targeting and synergistic neuromodulators in Ayurvedic herbs against epilepsy: integrated computational studies on drug-target and protein-protein interaction networks

Epilepsy, that comprises a wide spectrum of neuronal disorders and accounts for about one percent of global disease burden affecting people of all age groups, is recognised as apasmara in the traditional medicinal system of Indian antiquity commonly known as Ayurveda. Towards exploring the molecular level complex regulatory mechanisms of 63 anti-epileptic Ayurvedic herbs and thoroughly examining the multi-targeting and synergistic potential of 349 drug-like phytochemicals (DPCs) found therein, in this study, we develop an integrated computational framework comprising of network pharmacology and molecular docking studies. Neuromodulatory prospects of anti-epileptic herbs are probed and, as a special case study, DPCs that can regulate metabotropic glutamate receptors (mGluRs) are inspected. A novel methodology to screen and systematically analyse the DPCs having similar neuromodulatory potential vis-à-vis DrugBank compounds (NeuMoDs) is developed and 11 NeuMoDs are reported. A repertoire of 74 DPCs having poly-pharmacological similarity with anti-epileptic DrugBank compounds and those under clinical trials is also reported. Further, high-confidence PPI-network specific to epileptic protein-targets is developed and the potential of DPCs to regulate its functional modules is investigated. We believe that the presented schema can open-up exhaustive explorations of indigenous herbs towards meticulous identification of clinically relevant DPCs against various diseases and disorders.

Bioavailability Enhancement of Poorly Soluble Drugs: The Holy Grail in Pharma Industry

Background:

Bioavailability, one of the prime pharmacokinetic properties of a drug, is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation and is used to describe the systemic availability of a drug. Bioavailability assessment is imperative in order to demonstrate whether the drug attains the desirable systemic exposure for effective therapy. In recent years, bioavailability has become the subject of importance in drug discovery and development studies.

Methods:

A systematic literature review in the field of bioavailability and the approaches towards its enhancement have been comprehensively done, purely focusing upon recent papers. The data mining was performed using databases like PubMed, Science Direct and general Google searches and the collected data was exhaustively studied and summarized in a generalized manner.

Results:

The main prospect of this review was to generate a comprehensive one-stop summary of the numerous available approaches and their pharmaceutical applications in improving the stability concerns, physicochemical and mechanical properties of the poorly water-soluble drugs which directly or indirectly augment their bioavailability.

Conclusion:

The use of novel methods, including but not limited to, nano-based formulations, bio-enhancers, solid dispersions, lipid-and polymer-based formulations which provide a wide range of applications not only increases the solubility and permeability of the poorly bioavailable drugs but also improves their stability, and targeting efficacy. Although, these methods have drastically changed the pharmaceutical industry demand for the newer potential methods with better outcomes in the field of pharmaceutical science to formulate various dosage forms with adequate systemic availability and improved patient compliance, further research is required.

A census of P. longum's phytochemicals and their network pharmacological evaluation for identifying novel drug-like molecules against various diseases, with a special focus on neurological disorders

Piper longum (P. longum, also called as long pepper) is one of the common culinary herbs that has been extensively used as a crucial constituent in various indigenous medicines, specifically in traditional Indian medicinal system known as Ayurveda. For exploring the comprehensive effect of its constituents in humans at proteomic and metabolic levels, we have reviewed all of its known phytochemicals and enquired about their regulatory potential against various protein targets by developing high-confidence tripartite networks consisting of phytochemical—protein target—disease association. We have also (i) studied immunomodulatory potency of this herb; (ii) developed subnetwork of human PPI regulated by its phytochemicals and could successfully associate its specific modules playing important role in diseases, and (iii) reported several novel drug targets. P10636 (microtubule-associated protein tau, that is involved in diseases like dementia etc.) was found to be the commonly screened target by about seventy percent of these phytochemicals. We report 20 drug-like phytochemicals in this herb, out of which 7 are found to be the potential regulators of 5 FDA approved drug targets. Multi-targeting capacity of 3 phytochemicals involved in neuroactive ligand receptor interaction pathway was further explored via molecular docking experiments. To investigate the molecular mechanism of P. longum’s action against neurological disorders, we have developed a computational framework that can be easily extended to explore its healing potential against other diseases and can also be applied to scrutinize other indigenous herbs for drug-design studies.

Practical considerations when designing and conducting clinical pharmacokinetic herb–drug interaction studies

Pharmacokinetic herb–drug interaction (HDI) research has been ongoing for almost two decades and a significant body of information has been published on the subject, yet much of it is contradictory. Some of this disparity stems from the botanical dosage form itself, as product quality and dosage form performance can vary significantly among brands. Unless products are adequately characterized, HDI study results can be misleading. The purpose of this report is to identify several common weaknesses inherent in many prospective clinical HDI studies and to provide guidance in addressing these shortcomings. Topics such as study design, pharmacokinetic end points, product quality, dosage form performance, gauging clinical relevance, and efforts to minimize dietary influences while improving compliance are discussed.

Effect of piperine on CYP2E1 enzyme activity of chlorzoxazone in healthy volunteers

1. The purpose of the present study was to investigate the effect of piperine (PIP) on CYP2E1 enzyme activity and pharmacokinetics of chlorzoxazone (CHZ) in healthy volunteers. 2. An open-label, two period, sequential study was conducted in 12 healthy volunteers. A single dose of PIP 20 mg was administered daily for 10 days during treatment phase. A single dose of CHZ 250 mg was administered during control and after treatment phases under fasting conditions. The blood samples were collected at predetermined time intervals after CHZ dosing and analyzed by HPLC. 3. Treatment with PIP significantly enhanced maximum plasma concentration (C_max) (3.14-4.96 μg/mL)_, area under the curve (AUC) (10.46-17.78 μg h/mL), half life (T_1/2) (1.26-1.82 h) and significantly decreased elimination rate constant (K_el) (0.57-0.41 h ^- 1), apparent oral clearance (CL/F) (24.76-13.65 L/h) of CHZ when compared to control. In addition, treatment with PIP significantly decreased C_max (0.22-0.15 μg/mL), AUC (0.94-0.68 μg h/mL), T_1/2 (2.54-1.68 h) and significantly increased K_el (0.32-0.43 h ^- 1) of 6-hydroxychlorzoxazone (6-OHCHZ) as compared to control. Furthermore, treatment with PIP significantly decreased metabolite to parent (6-OHCHZ/CHZ) ratios of C_max, AUC, T_1/2 and significantly increased K_el ratio of 6-OHCHZ/CHZ, which indicate the decreased formation of CHZ to 6-OHCHZ. 4. The results suggest that altered pharmacokinetics of CHZ might be attributed to PIP mediated inhibition of CYP2E1 enzyme, which indicate significant pharmacokinetic interaction present between PIP and CHZ. The inhibition of CYP2E1 by PIP may represent a novel therapeutic benefit for minimizing ethanol induced CYP2E1 enzyme activity and results in reduced hepatotoxicity of ethanol.

Piperine metabolically regulates peritoneal resident macrophages to potentiate their functions against bacterial infection

Pepper, a daily-used seasoning for promoting appetite, is widely used in folk medicine for treating gastrointestinal diseases. Piperine is the major alkaloid in pepper and possesses a wide range of pharmacological activities. However, the mechanism for linking metabolic and medicinal activities of piperine remains unknown. Here we report that piperine robustly boosts mTORC1 activity by recruiting more system L1 amino acid transporter (SLC7A5/SLC3A2) to the cell membrane, thus promoting amino acid metabolism. Piperine-induced increase of mTORC1 activity in resident peritoneal macrophages (pMΦs) is correlated with enhanced production of IL-6 and TNF-α upon LPS stimulation. Such an enhancement of cytokine production could be abrogated by inhibitors of the mTOR signaling pathway, indicating mTOR's action in this process. Moreover, piperine treatment protected resident pMΦs from bacterium-induced apoptosis and disappearance, and increased their bacterial phagocytic ability. Consequently, piperine administration conferred mice resistance against bacterial infection and even sepsis. Our data highlight that piperine has the capacity to metabolically reprogram peritoneal resident macrophages to fortify their innate functions against bacterial infection.

Hot melt extrusion as an approach to improve solubility, permeability and oral absorption of a psychoactive natural product, piperine

OBJECTIVE

The aims of the current research project were to investigate the efficiency of various polymers to enhance the solubility and increase the systemic absorption of piperine using hot melt extrusion technology.

METHODS

Piperine 10-40% w/w and Eudragit(®) EPO/Kollidon(®) VA 64 or Soluplus(®) were mixed, and the resulting blends were extruded using a twin-screw extruder (Process 11, Thermo Fisher Scientific). Drug release profiles and piperine solubility studies of the extrudates were evaluated. A non-everted intestinal sac was employed for the most promising formulation, 10% w/w piperine/Soluplus(®) , and pure piperine to study the permeability characteristics.

KEY FINDINGS

Dissolution studies demonstrated enhancement in piperine per cent release of 10% and 20% w/w piperine/Soluplus(®) extrudates up to 95% and 74%, respectively. The solubility of 10% and 20% piperine/Soluplus(®) increased more than 160- and 45-fold in water, respectively. Furthermore, permeability studies demonstrated the enhancement in piperine absorption of 10% w/w piperine/Soluplus(®) extrudates up to 158.9 μg/5 ml compared with pure piperine at 1.3 μg/5 ml within 20 min.

CONCLUSION

These results demonstrated that increasing the bioavailability of piperine may be achieved as demonstrated by findings in this study.

Pharmacodynamic and pharmacokinetic interaction of Panchagavya Ghrita with phenytoin and carbamazepine in maximal electroshock induced seizures in rats

Introduction:

Traditionally, Panchagavya Ghrita (PG) has been used for the management of epilepsy, anxiety, fever and jaundice. It consists of five components of cow products namely, cow milk, clarified butter from cow milk, cow urine, curd from cow milk, and cow dung juice.

Aim:

To evaluate the effect of PG in maximal electroshock (MES) induced seizures model and its pharmacodynamic and pharmacokinetic interaction with phenytoin (PHT) and carbamazepine (CBZ) in rats.

Materials and Methods:

Male Wistar rats were administered PG 500, 1000, 2000, and 4000 mg/kg orally for 7 days and seizures were induced by MES. For interaction studies, PG (4000 mg/kg) was administered along with a sub-therapeutic dose of PHT (20 mg/kg, p.o.) and CBZ (10 mg/kg, p.o.). Behavioral parameters were assessed. Oxidative stress markers and serum levels of PHT and CBZ were estimated.

Results:

Tonic hind limb extension, cognitive impairment, and oxidative stress produced by MES were reversed by PG (4000 mg/kg). Co-administration of PG (4000 mg/kg) with a sub-therapeutic dose of PHT and CBZ potentiated antiepileptic effect and ameliorated cognitive impairment as well as oxidative stress. Although, there was a slight increase in serum levels of PHT and CBZ on co-administration with PG, it was statistically insignificant.

Conclusion:

Co-administration of PG with low doses of PHT and CBZ caused complete seizure protection. This suggests the potential of PG as an adjunct in epilepsy with improved efficacy and tolerability.

Lessons from black pepper: piperine and derivatives thereof

INTRODUCTION

Piperine is a simple and pungent alkaloid found in the seeds of black pepper (Piper nigrum). Following its isolation and full characterization, the biological properties of piperine have been extensively studied, and piperine-like derivatives have shown an interesting range of pharmacological activities. In this context, significant advances have been made in the discovery of new chemical entities based on the piperine scaffold endowed with therapeutic potential.

AREAS COVERED

The aim of this review is to provide a thorough inquiry on the therapeutic potential of piperine and related derivatives. It provides an overview of recent developments in patented processes and applications thereof between 2000 and 2015.

EXPERT OPINION

Cumulative evidence shows that piperine is currently paving its way to become a privileged scaffold for the development of bioactive compounds with therapeutic application in multiple human diseases. In particular, piperine derivatives were shown to modulate the activity of several targets related to neurological disorders, including epilepsy, Parkinson's disease, depression and pain related disorders. Moreover, the efflux pump inhibitory ability of piperine and its analogues tackles important drug resistance mechanisms and may improve the clinical efficacy of antibiotic and anticancer drugs. Although the use of piperine as a scaffold for bioactive compounds is still in its early stages, the continuous exploration of this structure may lead to remarkable advances in drug discovery programs.

Ayurveda and botanical drugs for epilepsy: Current evidence and future prospects

The understanding of epilepsy has progressed since its earliest impression as a disease associated with paranormal and superstitious beliefs. Landmark advances have been made in deciphering the pathophysiological substrates involved in the disease process, and treatment advances have contributed significantly to ameliorating the seizures. However, disease-modifying agents are yet to be discovered. Ayurveda is a system of medicine that stresses a holistic approach to disease, and treatment is focused on disease modification and symptom management. Herbs form the core of Ayurveda medicine; though many of them have been studied for their anticonvulsant activity, very few actually mention the reference of these herbs in Ayurveda literature. Other therapeutic interventions used in Ayurveda are relatively unexplored, and future research will need to focus on this. The current manuscript briefly discusses the understanding of epilepsy as per Ayurveda and reviews herbs that have been studied for their anticonvulsant activity mentioned in Ayurveda literature. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

Issues and promise in clinical studies of botanicals with anticonvulsant potential

Botanicals are increasingly used by people with epilepsy worldwide. However, despite abundant preclinical data on the anticonvulsant properties of many herbal remedies, there are very few human studies assessing safety and efficacy of these products in epilepsy. Additionally, the methodology of most of these studies only marginally meets the requirements of evidence-based medicine. Although the currently available evidence for the use of cannabinoids in epilepsy is similarly lacking, several carefully designed and well controlled industry-sponsored clinical trials of cannabis derivatives are planned to be completed in the next couple of years, providing the needed reliable data for the use of these products. The choice of the best botanical candidates with anticonvulsant properties and their assessment in well-designed clinical trials may significantly improve our ability to effectively and safely treat patients with epilepsy. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

Role of herbal bioactives as a potential bioavailability enhancer for Active Pharmaceutical Ingredients

The current review emphasizes on the herbal bioenhancers which themselves do not possess inherent pharmacological activity of their own but when co-administered with Active Pharmaceutical Ingredients (API), enhances their bioavailability and efficacy. Herbal bioenhancers play a crucial role in enhancing the bioavailability and bioefficacy of different classes of drugs, such as antihypertensives, anticancer, antiviral, antitubercular and antifungal drugs at low doses. This paper highlights various natural compounds that can be utilized as an efficient bioenhancer. Several herbal compounds including piperine, quercetin, genistein, naringin, sinomenine, curcumin, and glycyrrhizin have demonstrated capability to improve the pharmacokinetic parameters of several potent API. This article also focuses on various United States patents on herbal bioenhancers, which has proved to be beneficial in improving oral absorption of nutraceuticals like vitamins, minerals, amino acids and certain herbal compounds. The present paper also describes proposed mechanism of action, which mainly includes absorption process, drug metabolism, and action on drug target. The herbal bioenhancers are easily available, safe, free from side effects, minimizes drug toxicity, shortens the duration of treatment, lowers the drug resistance problems and minimizes the cost of treatment. Inspite of the fact that herbal bioenhancers provide an innovative concept for enhancing the bioavailability of several potent drugs, there are numerous bioenhancers of herbal origin that are yet to be explored in several vital areas. These bioenhancers must also be implied to enhance the bioavailability and bioefficacy through routes other than the oral route of drug delivery. There is a vast array of unexploited plants which can be investigated for their drug bioenhancing potency. The toxicity profiles of these herbal bioenhancers must not be overlooked. Researches must be carried out to solve these issues and to deliver a safe and effective dose of drugs to attain desired pharmacological response.

Enhanced oral bioavailability of piperine by self-emulsifying drug delivery systems: in vitro, in vivo and in situ intestinal permeability studies

The main purpose of this work was to develop and evaluate a self-emulsifying drug delivery system (SEDDS) of piperine to enhance its solubility and bioavailability. The formulation was optimized by solubility test and ternary phase diagrams. Then physiochemical properties and in vitro release of SEDDS were characterized. In vivo pharmacokinetics study and in situ single-pass intestinal perfusion were performed to investigate the effects of SEDDS on the bioavailability and intestinal absorption of piperine. The optimized formulation was composed of ethyl oleate, Tween 80 and Transcutol P (3:5.5:1.5, w/w), with the level of the piperine reached 2.5% (w/w). The in vitro dissolution rates of piperine SEDDS were significantly higher than the self-prepared capsules. In vivo pharmacokinetic study showed Cmax1, Cmax2 and area under the curve of piperine after oral administration of SEDDS in rats were 3.8-, 7.2- and 5.2-fold higher than the self-prepared capsules, respectively, and the relative bioavailability of SEDDS was 625.74%. The in situ intestinal absorption study revealed that the effective permeability and the effective absorption rate values of piperine for SEDDS were significantly improved comparing to solutions (p < 0.01). So SEDDS formulation could improve the oral bioavailability and intestinal absorption of piperine effectively.

The effect of piperine on midazolam plasma concentration in healthy volunteers, a research on the CYP3A-involving metabolism

Some studies showed that piperine (the alkaloid of piper nigrum) can change the activities of microsomal enzymes. Midazolam concentration is applied as a probe to determine the CYP3A enzyme activity. This study was done to determine piperine pretreatment role on midazolam plasma concentration.Twenty healthy volunteers (14 men and 6 women) received oral dose of piperine (15 mg) or placebo for three days as pretreatment and midazolam (10 mg) on fourth day of study and the blood samples were taken at 0.5, 2.5 and 5 h after midazolam administration. The midazolam plasma levels were assayed using HPLC method (C18 analytical column, 75:25 methanol:water as mobile phase, UV detector at 242 nm wavelength and diazepam as internal standard). Data were fit in a "one-compartment PK model" using P-Pharm 1.5 software and analyzed under statistical tests.The mean ±SD of the age and body mass index were 24.3 ± 1.83 years (range: 21-28 years) and 23.46± 2.85, respectively. The duration of sedation in piperine receiving group was greater that the placebo group (188±59 vs. 102±43 min, p<0.0001). Half-life and clearance of midazolam were higher in piperine pretreatment group compared to placebo [1.88±0.03 vs. 1.71± 0.04 h (p<0.0001) and 33.62 ± 0.4 vs. 37.09 ± 1.07 ml/min (p<0.0001), respectively].According to the results, piperine can significantly increases half-life and decreases clearance of midazolam compared to placebo. It is suggested that piperine can demonstrate those effects by inhibition CYP3A4 enzyme activity in liver microsomal system.

Adipogenic effects of piperlonguminine in 3T3-L1 cells and plasma concentrations of several amide constituents from Piper chaba extracts after treatment of mice

In our previous study, piperlonguminine from the fruit of Piper chaba was reported to promote adipogenesis in 3T3-L1 cells like the peroxisome proliferator-activated receptor-γ (PPARγ) agonist, troglitazone. In the present study, the mode of action of piperlonguminine in cells was examined. Piperlonguminine increased mRNA levels of adiponectin, glucose transporter 4, and fatty acid-binding protein (aP2). It also increased mRNA levels of PPARγ2 but, unlike troglitazone, piperlonguminine did not activate PPARγ directly in a nuclear receptor cofactor assay. Analyses of plasma from mice treated with piperlonguminine, piperine, and retrofractamide A, and an extract of the fruit, showed that concentrations of piperlonguminine were higher than those of piperine and retrofractamide A, and that the "area-under-the-curve" of piperine increased following in vivo administration of the extract.

Efficacy of Iranian traditional medicine in the treatment of epilepsy

Epilepsy is a brain disorder which affects about 50 million people worldwide. Ineffectiveness of the drugs in some cases and the serious side effects and chronic toxicity of the antiepileptic drugs lead to use of herbal medicine as a form of complementary and alternative medicine. In this review modern evidences for the efficacy of antiepileptic medicinal plants in Traditional Iranian Medicine (TIM) will be discussed. For this purpose electronic databases including PubMed, Scopus, Sciencedirect, and Google Scholar were searched for each of the antiepileptic plants during 1970-February 2013.Anticonvulsant effect of some of the medicinal plants mentioned in TIM like Anacyclus pyrethrum, Pimpinella anisum, Nigella sativa, and Ferula gummosa was studied with different models of seizure. Also for some of these plants like Nigella sativa or Piper longum the active constituent responsible for antiepileptic effect was isolated and studied. For some of the herbal medicine used in TIM such as Pistacia lentiscus gum (Mastaki), Bryonia alba (Fashra), Ferula persica (Sakbinaj), Ecballium elaterium (Ghesa-al Hemar), and Alpinia officinarum (Kholanjan) there is no or not enough studies to confirm their effectiveness in epilepsy. It is suggested that an evaluation of the effects of these plants on different epileptic models should be performed.

Piperine activates human pregnane X receptor to induce the expression of cytochrome P450 3A4 and multidrug resistance protein 1

Activation of the pregnane X receptor (PXR) and subsequently its target genes, including those encoding drug transporters and metabolizing enzymes, while playing substantial roles in xenobiotic detoxification, might cause undesired drug-drug interactions. Recently, an increased awareness has been given to dietary components for potential induction of diet-drug interactions through activation of PXR. Here, we studied, whether piperine (PIP), a major component extracted from the widely-used daily spice black pepper, could induce PXR-mediated expression of cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1). Our results showed that PIP activated human PXR (hPXR)-mediated CYP3A4 and MDR1 expression in human hepatocytes, intestine cells, and a mouse model; PIP activated hPXR by recruiting its coactivator SRC-1 in both cellular and cell-free systems; PIP bound to the hPXR ligand binding domain in a competitive ligand binding assay in vitro. The dichotomous effects of PIP on induction of CYP3A4 and MDR1 expression observed here and inhibition of their activity reported elsewhere challenges the potential use of PIP as a bioavailability enhancer and suggests that caution should be taken in PIP consumption during drug treatment in patients, particularly those who favor daily pepper spice or rely on certain pepper remedies.

Piper nigrum and piperine: an update

Black pepper (Piper nigrum L.) is a very widely used spice, known for its pungent constituent piperine. However, in addition to its culinary uses, pepper has important medicinal and preservative properties, and, more recently, piperine has been shown to have fundamental effects on p-glycoprotein and many enzyme systems, leading to biotransformative effects including chemoprevention, detoxification, and enhancement of the absorption and bioavailability of herbal and conventional drugs. Based on modern cell, animal, and human studies, piperine has been found to have immunomodulatory, anti-oxidant, anti-asthmatic, anti-carcinogenic, anti-inflammatory, anti-ulcer, and anti-amoebic properties. In this review, the chemical constituents, biological activities, effects of processing, and future potential of black pepper and piperine have been discussed thoroughly.

Effect of a herbal extract containing curcumin and piperine on midazolam, flurbiprofen and paracetamol (acetaminophen) pharmacokinetics in healthy volunteers

AIMS

Turmeric extract derived curcuminoids (curcumin, demethoxycurcumin and bisdemethoxycurcumin) are currently being evaluated for the treatment of cancer and Alzheimer's dementia. Previous in vitro studies indicate that curcuminoids and piperine (a black pepper derivative that enhances curcuminoid bioavailability) could inhibit human CYP3A, CYP2C9, UGT and SULT dependent drug metabolism. The aim of this study was to determine whether a commercially available curcuminoid/piperine extract alters the pharmacokinetic disposition of probe drugs for these enzymes in human volunteers.

METHODS

A randomized placebo-controlled six way crossover study was conducted in eight healthy volunteers. A standardized curcuminoid/piperine preparation (4 g curcuminoids plus 24 mg piperine) or matched placebo was given orally four times over 2 days before oral administration of midazolam (CYP3A probe), flurbiprofen (CYP2C9 probe) or paracetamol (acetaminophen) (dual UGT and SULT probe). Plasma and urine concentrations of drugs, metabolites and herbals were measured by HPLC. Subject sedation and electroencephalograph effects were also measured following midazolam dosing.

RESULTS

Compared with placebo, the curcuminoid/piperine treatment produced no meaningful changes in plasma C(max), AUC, clearance, elimination half-life or metabolite levels of midazolam, flurbiprofen or paracetamol (α = 0.05, paired t-tests). There was also no effect of curcuminoid/piperine treatment on the pharmacodynamics of midazolam. Although curcuminoid and piperine concentrations were readily measured in plasma following glucuronidase/sulfatase treatment, unconjugated concentrations were consistently below the assay thresholds (0.05-0.08 μM and 0.6 μM, respectively).

CONCLUSION

The results indicate that short term use of this piperine-enhanced curcuminoid preparation is unlikely to result in a clinically significant interaction involving CYP3A, CYP2C9 or the paracetamol conjugation enzymes.

A comprehensive review on pharmacotherapeutics of herbal bioenhancers

In India, Ayurveda has made a major contribution to the drug discovery process with new means of identifying active compounds. Recent advancement in bioavailability enhancement of drugs by compounds of herbal origin has produced a revolutionary shift in the way of therapeutics. Thus, bibliographic investigation was carried out by analyzing classical text books and peer-reviewed papers, consulting worldwide-accepted scientific databases from last 30 years. Herbal bioenhancers have been shown to enhance bioavailability and bioefficacy of different classes of drugs, such as antibiotics, antituberculosis, antiviral, antifungal, and anticancerous drugs at low doses. They have also improved oral absorption of nutraceuticals like vitamins, minerals, amino acids, and certain herbal compounds. Their mechanism of action is mainly through absorption process, drug metabolism, and action on drug target. This paper clearly indicates that scientific researchers and pharmaceutical industries have to give emphasis on experimental studies to find out novel active principles from such a vast array of unexploited plants having a role as a bioavailability and bioefficacy enhancer. Also, the mechanisms of action by which bioenhancer compounds exert bioenhancing effects remain to be explored.

Overview for various aspects of the health benefits of Piper longum linn. fruit

Herbal remedies have become popular, due in part to the lower risk of adverse reactions. Thousands of plants have been used traditionally to treat various diseases. Among them, species of the genus Piper are important medicinal plants used in various systems of medicine. The Piper longum fruit has been used in traditional medicine, including the Ayurvedic system of medicine. Although there are numerous indications for its use, controlled trials are needed to determine its efficacy. The primary constituents isolated from various parts of P. longum are piperine, piperlongumine, sylvatin, sesamin, diaeudesmin piperlonguminine, pipermonaline, and piperundecalidine. It is most commonly used to treat chronic bronchitis, asthma, constipation, gonorrhea, paralysis of the tongue, diarrhea, cholera, chronic malaria, viral hepatitis, respiratory infections, stomachache, bronchitis, diseases of the spleen, cough, and tumors. This study provides detailed information about the P. longum fruit, including phytochemistry, pharmacological profile and safety profile. In view of the commercial, economic, and medicinal importance of the P. longum plant, it is useful for researchers to study the plant in detail.

Dose and duration of nerve growth factor (NGF) administration determine the extent of behavioral recovery following peripheral nerve injury in the rat

Nerve growth factor (NGF) has been previously shown to support neuron survival and direct neurite outgrowth in vitro, and to enhance axonal regeneration in vivo. However, a systematic analysis of NGF dose and dose duration on behavioral recovery following peripheral nerve injury in rodents has not been previously investigated. Here, we show that NGF promotes a bell shaped dose-response, with an optimal threshold effect occurring at 800 pg/μl. High dose NGF inhibited regeneration. However, this effect could be reversed through functional blockade of p75 receptors, thus implicating these receptors as mediators of the inhibitory response. Longer term evaluation showed that animals administered NGF at 80 ng/day for 3 weeks had greater sensorimotor recovery compared to all other treatment groups. These animals made significantly fewer errors during skilled locomotion, and displayed both increased vertical and fore-aft ground reaction forces during flat surface locomotion. Furthermore, terminal electrophysiological and myological assessments (EMG, wet gastrocnemius muscle weights) corroborated the behavioral data. Overall, these data support the hypothesis that both appropriate dose and duration of NGF are important determinants of behavioral recovery following nerve injury in the rat.

Herb-drug pharmacokinetic interactions reviewed

IMPORTANCE OF THE FIELD

the global increase in the popularity of alternative medicines has raised renewed concerns regarding herb-drug interactions. These interactions are especially important for drugs with narrow therapeutic indices and may either be pharmacodynamic or pharmacokinetic in nature.

AREAS COVERED IN THIS REVIEW

pharmacokinetic interactions which may exist between herbs and drugs, and the mechanisms of these interactions with appropriate examples based on primary and secondary data in publications are discussed. The mechanisms covered include those that affect oral drug absorption (e.g., modulation of efflux and uptake transporters, complex formation, gastrointestinal motility and pH) and drug biotransformation (e.g., inhibition or induction of enzymes).

WHAT THE READER WILL GAIN

knowledge on the mechanisms of herb-drug pharmacokinetic interactions supported by an extended list of these types of interactions for quick reference. A critical evaluation of certain herb-drug pharmacokinetic interactions reported in the scientific literature.

TAKE HOME MESSAGE

as the incidence and severity of herb-drug pharmacokinetic interactions increase due to a worldwide rise in the use of herbal preparations, more clinical data regarding herb-drug pharmacokinetic interactions are needed to make informed decisions regarding patient safety.

Clinically based evidence of drug-herb interactions: a systematic review

IMPORTANCE OF THE FIELD

Healthcare practitioners are deeply concerned about drug-herb interactions and how concurrent administration may affect both the safety and effectiveness of prescribed drugs. Interactions between botanical medicines and synthetic drugs can be clinically relevant and it is important to understand what kinds of interactions are possible. Better knowledge in this area will help avoid negative interactions and may also help enable synergistic interactions.

AREAS COVERED IN THIS REVIEW

Includes articles related to the investigation of Western botanicals or whole herbal extracts in human subjects, investigating either the impact on Cytochrome P450 isoenzymes or an assessment of specific drug-herb interactions within a clinical trial. Searches were conducted in both Pubmed and EMBASE from inception to March 2009.

WHAT THE READER WILL GAIN

Knowledge regarding specific interactions to consider in clinical practice. The reader will also gain an appreciation of the complexities associated with the area of drug-herb interactions. Summary tables of relevant drug-herb interactions are presented both for the individual herbs included and at the level of the CYP450 enzymes.

TAKE HOME MESSAGE

Knowledge of drug-herb interactions is limited and much more research needs to be done to further document clinically relevant interactions. Even though preclinical data are often poorly generalizable to the human situation, caution must be taken in the absence of clinical evidence especially where drugs with narrow therapeutic windows are concerned.

Nanolipidic particles improve the bioavailability and alpha-secretase inducing ability of epigallocatechin-3-gallate (EGCG) for the treatment of Alzheimer's disease

Prevention of amyloidogenic processing of amyloid precursor protein with the use of natural phytochemicals capable of enhancing alpha-secretase activity may be a therapeutic approach for treatment of neurodegenerative diseases including Alzheimer's disease (AD) and HIV-associated dementia (HAD). We have recently shown promising preclinical results with the use of green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG) in mouse models of both diseases, however the translation into clinical use has been problematic primarily as a result of poor bioavailability and inefficient delivery to the central nervous system (CNS). While the antioxidant properties of EGCG are well known, we have shown that it is able to promote non-amyloidogenic processing of amyloid precursor protein (APP) by upregulating alpha-secretase, thus preventing brain beta amyloid plaque formation, a hallmark of AD pathology and common finding in HIV infection. In this preliminary study, we investigated the ability of one preformulation method to improve the oral bioavailability of EGCG. We found that forming nanolipidic EGCG particles improves the neuronal (SweAPP N2a cells) alpha-secretase enhancing ability in vitro by up to 91% (P<001) and it's oral bioavailability in vivo by more than two-fold over free EGCG.

Analysis by HPLC and LC/MS of pungent piperamides in commercial black, white, green, and red whole and ground peppercorns

Pepper plants accumulate pungent bioactive alkaloids called piperamides. To facilitate studies in this area, high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry methods were developed and used to measure the following piperamides in 10 commercial whole (peppercorns) and in 10 ground, black, white, green, and red peppers: piperanine, piperdardine, piperine, piperlonguminine, and piperettine. Structural identification of individual compounds in extracts was performed by associating the HPLC peak of each compound with the corresponding mass spectrum. The piperanine content of the peppers (in mg/g piperine equivalents) ranged from 0.3 for the ground white pepper to 1.4 in black peppercorns. The corresponding range for piperdardine was from 0.0 for seven samples to 1.8 in black peppercorns; for four isomeric piperines, from 0.7 for red to 129 in green peppercorns; for piperlonguminine, from 0.0 in red peppercorns to 1.0 in black peppercorns; and for piperyline, from 0.9 in ground black pepper to 5.9 for red peppercorn. Four well-separated stereoisomeric forms of piperettine with the same molecular weight were present in 19 peppers. The sums of the piperamides ranged from 6.6 for red to 153 for green peppercorns. In contrast to large differences in absolute concentrations among the peppers, the ratios of piperines to total piperamide were quite narrow, ranging from 0.76 for black to 0.90 for white peppercorns, with an average value of 0.84 +/- 0.04 ( n = 19). Thus, on average, the total piperamide content of the peppers consists of 84% piperines and 16% other piperamides. These results demonstrate the utility of the described extraction and analytical methods used to determine the wide-ranging individual and total piperamide contents of widely consumed peppers.

Curcuminoids inhibit multiple human cytochromes P450, UDP-glucuronosyltransferase, and sulfotransferase enzymes, whereas piperine is a relatively selective CYP3A4 inhibitor

Curcuminoid extract and piperine are being evaluated for beneficial effects in Alzheimer's disease, among other intractable disorders. Consequently, we studied the potential for herb-drug interactions involving cytochrome P450 (P450), UDP-glucuronosyltransferase (UGT), and sulfotransferase (SULT) enzymes. The curcuminoid extract inhibited SULT > CYP2C19 > CYP2B6 > UGT > CYP2C9 > CYP3A activities with IC(50) values ranging from 0.99 +/- 0.04 to 25.3 +/- 1.3 microM, whereas CYP2D6, CYP1A2, and CYP2E1 activities were less affected (IC(50) values > 60 microM). Inhibition of CYP3A activity by curcuminoid extract was consistent with competitive inhibition (K(i) = 11.0 +/- 1.3 microM), whereas inhibition of both CYP2C9 and CYP2C19 activities were consistent with mixed competitive-noncompetitive inhibition (10.6 +/- 1.1 and 7.8 +/- 0.9 microM, respectively). Piperine was a relatively selective noncompetitive inhibitor of CYP3A (IC(50) 5.5 +/- 0.7 microM, K(i) = 5.4 +/- 0.3 microM) with less effect on other enzymes evaluated (IC(50) > 29 microM). Curcuminoid extract and piperine inhibited recombinant CYP3A4 much more potently (by >5-fold) than CYP3A5. Pure synthetic curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) were also evaluated for their effects on CYP3A, CYP2C9, UGT, and SULT activities. All three curcuminoids had similar effects on CYP3A, UGT, and SULT activity, but demethoxycurcumin (IC(50) = 8.8 +/- 1.2 microM) was more active against CYP2C9 than either curcumin or bisdemethoxycurcumin (IC(50) > 50 microM). Based on these data and expected tissue concentrations of inhibitors, we predict that a p.o. administered curcuminoid/piperine combination is most likely to inhibit CYP3A, CYP2C9, UGT, and SULT metabolism within the intestinal mucosa.

Herbal medicine and epilepsy: proconvulsive effects and interactions with antiepileptic drugs

The use of complementary and alternative medicine is on the rise, including among patients with epilepsy. Herbal medicine, one of the most popular forms of CAM, is considered to be both safe and effective by most consumers. Yet many herbs may increase the risk for seizures, through intrinsic proconvulsant properties or contamination by heavy metals, as well as via effects on the cytochrome P450 enzymes and P-glycoproteins, altering antiepileptic drug (AED) disposition. Herb-drug interactions may be difficult to predict, especially since the quality and quantity of active ingredients are often unknown. Since most patients do not inform their physicians that they are taking herbal medicines, health care professionals must initiate a dialogue in order to prevent complications with the combined regimen. At the same time, further research is required regarding the effect of herbs on seizure activity and interactions with AED treatment.

Kinetics of light-induced cis-trans isomerization of four piperines and their levels in ground black peppers as determined by HPLC and LC/MS

The pungent compounds piperine and isomers thereof, secondary metabolites present in black and white pepper fruit, undergo light-induced isomerizations. To facilitate studies in this area, an HPLC method has been developed for analysis and isolation of the following four possible piperine-derived photoinduced isomers: piperine, isopiperine, chavicine, and isochavicine. The limits of detection (LOD) estimated from calibration plots were approximately 15-30 ng for each isomer. Reproducibilities of the analyses were excellent, and recoveries of spiked samples were as follows (average +/- SD; n = 3): chavicine, 98.4 +/- 2.1%; isopiperine, 96.2 +/- 3.2%; piperine, 104 +/- 3.8%; isochavicine, 98.9 +/- 3.0%. To determine the kinetics of these isomerizations, fluorescent light, sunlight, and UV radiation at 254 nm was used to induce cis-trans geometric isomerization as a function of light intensities and time of exposure determined with the aid of high-performance liquid chromatography (HPLC) and liquid chromatography with diode array UV detection-mass spectrometry (LC-DAD/MS). HPLC was also used to determine the distribution of the isomers in four commercial ground black pepper products used as spices in culinary practice. Isomerization increased with light intensities and time of exposure and leveled off at the so-called photostationary phases. The piperine levels of the four products were quite similar, ranging (in wt %) from 10.17 to 11.68. The amounts of the other three isomers ranged from 0.01 to 0.07 of the total for chavicine; from 0.15 to 0.23 for isopiperine; and from 0.37 to 0.42 for isochavicine. The results establish the utility of the HPLC method for simultaneous analysis of the four isomers both in pure form and in black pepper extracts. The dietary significance of the results is discussed.