Piperoylpiperidine (Piperine): A Comprehensive Reference
1. Identity
Chemical and Botanical Names
Piperoylpiperidine is the systematic chemical name for the natural alkaloid more widely known as piperine. Piperine is the trans-trans stereoisomer of 1-piperoylpiperidine, also known as (E,E)-1-piperoylpiperidine and (E,E)-1-[5-(1,3-benzodioxol-5-yl)-1-oxo-2,4-pentadienyl]piperidine. Its molecular formula is C17H19NO3. Additional synonyms in chemical literature and regulatory databases include 1-piperylpiperidine, piperylpiperidine, Bioperine (a proprietary standardised extract), Piperin, and NSC 21727. The compound is registered under CAS number 94-62-2 and FEMA number 2909.
Natural Sources
Piperine is the predominant dietary alkaloid found in the fruits and roots of Piper nigrum L. (black pepper) and Piper longum L. (long pepper), species of the family Piperaceae. It is responsible for the characteristic pungency and biting taste of pepper. Black pepper, known as the "King of Spices," has an estimated worldwide production of approximately 0.75 million tonnes and is considered the major commercial source of piperine.
Piperine has also been found in other plants of the Piperaceae family; its content ranges from 2% to 7.4% depending on the variety, with literature reporting piperine levels of 4–5% in long pepper and up to 9% in black pepper. The piperine content in peppers depends greatly on climatic conditions, place of origin, and conditions of drying.
Physical and Chemical Properties
In pure form, piperine exists as a yellow to pale-yellow crystal, with a burning taste and pungent odour. Piperine forms monoclinic needles, is slightly soluble in water (40 mg/L at 18 °C), and more soluble in alcohol (1 g/15 mL), ether (1 g/36 mL), and chloroform (1 g/1.7 mL); a solution in alcohol has a pepper-like taste. Piperine can be hydrolyzed by alkali into piperidine and piperic acid.
Discovery and Isolation
Piperine was discovered in 1819 by Hans Christian Ørsted, who isolated it from the fruits of Piper nigrum, the source plant of both black and white pepper grains.
Common Forms and Preparations
Piperine is commercially available in several forms for dietary supplement and research applications:
- Standardised black pepper extract (BioPerine® and generics): These preparations may be obtained as an extract from the fruit of Piper nigrum comprising at least 98% piperine.
- Long pepper extract: Preparations may also be derived from an extract of the fruit of Piper longum.
- Synthetic piperine: Synthetically produced piperine is also used in research and supplement formulations.
- Nanoformulations: Emerging preparations include piperine nanoparticles and nanocomposites developed to address the compound's pharmacokinetic limitations.
2. Traditional and Historical Use
Indian Subcontinent: Ayurveda, Siddha, Unani
Black pepper and long pepper are widely used in the traditional Ayurveda, Siddha, Unani, and Tibetan systems of medicine, where piperine, the active alkaloid present in pepper species, is used as a bioenhancer. Long pepper is an important medicine in Indian systems of medicine including Ayurveda, Unani, and Siddha, and its medicinal use in Ayurveda is over 4,000 years old.
In Ayurvedic medicine, black pepper has been used to aid digestion, improve appetite, and treat coughs, colds, breathing and heart problems, colic, diabetes, anaemia, and piles; stomach ailments such as dyspepsia, flatulence, constipation, and diarrhoea are all treated with black pepper, which may be mixed with other substances such as castor oil, cow's urine, or ghee.
Black peppercorns feature as remedies in Ayurveda, Siddha, and Unani medicine in South Asia, where they are most frequently used as an appetizer and to treat problems associated with the digestive system, particularly to eradicate parasitic worms. In Unani medicine, black pepper has been described as an aphrodisiac and as a remedy to alleviate colic.
In traditional medicine, including Ayurveda, Unani, Siddha, and Naturopathy, black pepper (P. nigrum) is used to formulate medicines for treating cough, cold, fever, teeth-acne, pain, sore throat, inflammation, acute sinusitis, asthma, and bronchitis.
The Trikatu Formulation
"Trikatu" is a famous Ayurvedic formula combining black pepper (Piper nigrum), long pepper (Piper longum), and ginger (Zingiber officinale); this formula is used to stimulate circulation, digestion, and for lung problems accompanied by sticky mucus. The formulation has been used individually or collectively to enhance the bioavailability of a large number of nutrients, including ingredients of vasaka leaves, vasicine, and sulfadiazine, in both animal and human volunteers.
Respiratory Diseases
Long pepper has been used to treat chronic bronchitis, cough, cold, palsy, gout, rheumatism, and lumbago. Long pepper differs little in its medicinal values from P. nigrum, being less aromatic and more acrid, and is widely used in Siddha, Ayurveda, and Unani systems of medicine, particularly for diseases of the respiratory tract. A common use of the fruit in the Charaka Samhita tradition is in the prevention of recurrent attacks of bronchial asthma and in malaria.
3. Key Constituents and Active Compounds
Principal Alkaloid
Piperine is a type of amide alkaloid that exhibits pleiotropic properties, including antioxidant, anticancer, anti-inflammatory, antihypertensive, hepatoprotective, neuroprotective, and bioavailability-enhancing activities. Along with its isomer chavicine, piperine from black pepper and long pepper produces pungency effects via activation of TRPV1.
Related Piperamide Compounds
In addition to piperine, there is an orthologous enzyme with broader substrate specificity in Piper nigrum called a "piperamide synthase," which is responsible for the many piperamide compounds found in black pepper besides piperine itself.
Metabolic Pathway
Piperic acid, piperonyl alcohol, piperonal, piperonylic acid, and vanillic acid are the major constituents along with their conjugates identified during the metabolic pathway of piperine; hydrolysis in the liver produces piperic acid, which may undergo oxidation of its side chain to form piperonylic acid, with first absorption marked in the portal vein.
4. Mechanisms of Action
Bioavailability Enhancement
Piperine may enhance drug bioavailability by promoting rapid absorption by increasing blood supply to the gastrointestinal tract, decreasing hydrochloric acid secretion to prevent the breakdown of some drugs, increasing the emulsifying content of the gut, and increasing enzymes like γ-glutamyl transpeptidase, which participate in active and passive transport of nutrients to intestinal cells.
Piperine may act as a potent bioavailability enhancer by inhibiting the P-glycoprotein-mediated efflux mechanism; inhibition of piperine and P-glycoprotein efflux may be a potentially beneficial therapeutic effect for the intestinal absorption of drugs that are poorly absorbable. This results in a change of permeation properties of the intestine, enabling compounds with low bioavailability due to lower membrane crossing to be better absorbed; piperine may also directly increase the intestinal absorptive surface through induction of synthesis of proteins associated with cytoskeletal function of intestinal epithelial cells.
Inhibition of Drug-Metabolising Enzymes
Piperine (1-piperoylpiperidine) is reported to be an inhibitor of human CYP3A4 and MDR1, resulting in increased bioavailability of orally co-administered drugs that are CYP3A4 and MDR1 substrates. Piperine is a known inhibitor of glucuronidation in the liver and intestine. Piperine inhibits the CYP3A4-catalyzed formation of verapamil metabolites in human liver microsomes; this inhibition is relatively selective, being more potent against CYP3A4 with an IC50 of 2.12 µM compared to CYP1A2 and CYP2C9 with IC50 values of 14.19 and 89.62 µM, respectively.
TRPV1 Agonism
Piperine is known for its pungency and action on transient receptor potential vanilloid (TRPV) ion channels. TRPV1 is the same receptor activated by capsaicin from chili peppers, and piperine's agonism at this receptor underlies its pungent sensory properties and is proposed to contribute to thermogenesis, pain modulation, and other physiological effects.
Monoamine Oxidase (MAO) Inhibition
Research suggests that piperine possesses antidepressant-like properties that are mediated in part through the inhibition of MAO activity. MAO has two isoforms, -A and -B; selective inhibition of MAO-B offers a therapeutic benefit in Alzheimer's and Parkinson's disease treatment, while MAO-A inhibition provides benefits in depression and anxiety. Among all explored natural products, piperine has been extensively studied for MAO inhibition and has shown significant potential as a candidate for neurological disorders.
Anti-Inflammatory Mechanisms
Piperine inhibits the expression of IL-6 and MMP13, and reduces the production of PGE2 in a dose-dependent manner at concentrations of 10–100 µg/ml; production of PGE2 was significantly inhibited even at 10 µg/ml, and piperine inhibited the migration of activator protein 1 (AP-1), but not NF-κB, into the nucleus in IL-1β-treated synoviocytes. Piperine also modulates inflammatory and oxidative stress responses by inhibiting NF-κB and activating Nrf2/Keap1 signalling while reducing angiogenesis via Src/EGFR-IL-8 regulation.
Anticancer Mechanisms
Piperine is known to affect cancer cells by influencing redox homeostasis, inhibiting cancer stem cell self-renewal, modulating endoplasmic reticulum (ER) stress and autophagy, and modifying the activity of many enzymes and transcription factors to inhibit invasion, metastasis, and angiogenesis. Piperine is also a potent inhibitor of P-glycoprotein (P-gp) and has a significant effect on the drug-metabolising enzyme (DME) system; because of its inhibitory influence on P-gp activity, piperine can reverse multidrug resistance in cancer cells and acts as a bioavailability enhancer for many chemotherapeutic agents.
Melanocyte Stimulation
Piperine, the major alkaloid found in the fruit of black pepper, stimulates the replication of melanocytes and induces the formation of melanocytic dendrites, and is expected to cause repopulation of vitiligo patches through a stimulatory effect on perilesional and follicular melanocytes.
5. Scientific Evidence by Area of Use
5.1 Bioavailability Enhancement
Evidence level: Strong clinical evidence for specific co-administered compounds; mechanistic evidence well established.
The most robust and well-replicated human clinical evidence for piperine concerns its role as a bioenhancer. In a clinical study, 2 g of curcumin administered concomitantly with 20 mg of piperine, an inhibitor of hepatic and intestinal glucuronidation, produced a significant 2,000% increase in the oral bioavailability of curcumin. The effect of piperine on pharmacokinetics was found to be much greater in humans than in rats; in humans, curcumin bioavailability was increased by 2,000% at 45 minutes after co-administration, whereas in rats, piperine at 20 mg/kg increased serum curcumin concentration by 154%.
The study showed that in the dosages used, piperine enhanced the serum concentration, extent of absorption, and bioavailability of curcumin in both rats and humans with no reported adverse effects. However, a more recent independent crossover study in nine healthy males found that piperine addition provided no benefit in certain advanced curcumin formulations, indicating that the magnitude of enhancement may depend on the specific curcumin formulation used and that the commonly cited 2,000% figure has been questioned. The 'curcumin only' control group in the landmark study returned results below the limit of detection for serum curcumin, and the 2,000% increase was based on AUC measurement; it is not clear from this study what assumptions were made regarding non-detects in serum when estimating AUC.
Beyond curcumin, clinical evidence extends to other drugs. In a human study, participants were pretreated with 20 mg of piperine daily for seven days before receiving 150 mg of theophylline or 300 mg of phenytoin; the maximum concentration of theophylline was 1.5 times higher in subjects pretreated with piperine, and the elimination rate of the drug was significantly slowed. In the case of propranolol, co-administration with only 3 mg of piperine resulted in doubling its blood levels, but without slowing down the drug elimination rate. In another study, 12 healthy subjects took a single 120-mg dose of fexofenadine before and after administration of piperine 20 mg/d for 10 days; with piperine pretreatment, fexofenadine AUC increased by 68%.
A dose of 20 mg/day of piperine administered for 10 consecutive days increased the AUC of carbamazepine by 47% compared to carbamazepine alone in healthy volunteers. Pretreatment with piperine at 15 mg/day for three consecutive days elevated the AUC0–5h of midazolam by 20% compared to midazolam administered without piperine in healthy subjects.
5.2 Anti-Inflammatory and Antioxidant Activity
Evidence level: Preclinical (in vitro and animal) evidence is extensive; human clinical evidence is preliminary and primarily obtained via combination studies with curcumin.
Piperine has been employed in various animal models, including carrageenan-induced rat paw oedema, cotton pellet granuloma, croton oil-induced granuloma pouch, formalin-induced arthritis, high-fat diet-induced inflammation in subcutaneous adipose tissue, and IL-1β-induced expression of inflammatory mediators, and UV-B-induced inflammatory responses in human skin for anti-inflammatory activities.
In human studies, piperine has predominantly been studied as an adjuvant to curcumin. In a randomised double-blind placebo-controlled trial, 117 subjects with metabolic syndrome were randomly assigned to curcuminoids (n = 59) or placebo (n = 58) for eight weeks; curcuminoids were administered at a daily dose of 1 g, and were co-supplemented with piperine (10 mg/day) to boost oral bioavailability, with measurement of superoxide dismutase, malondialdehyde, and CRP at baseline and study end.
5.3 Arthritis and Joint Inflammation
Evidence level: Preclinical evidence is moderate to strong; limited human clinical trial evidence has been reported.
In rat models of carrageenan-induced pain and arthritis, piperine significantly reduced nociceptive and arthritic symptoms, and histological staining showed that piperine significantly reduced the inflammatory area in the ankle joints. These results suggest piperine has anti-inflammatory, antinociceptive, and antiarthritic effects in an arthritis animal model and should be further studied as a pharmaceutical or dietary supplement for arthritis treatment. Some clinical trials have yielded promising results, confirming piperine's efficacy in conditions including osteoarthritis.
5.4 Vitiligo (Skin Depigmentation)
Evidence level: Meaningful translational and early clinical evidence; one published double-blind clinical trial in humans.
Piperine was discovered as a potential treatment for vitiligo through research and testing of herbal extracts, where a water extract of black pepper was found to stimulate melanocyte growth and dendrite formation; the compound responsible was identified as piperine, and it was validated as a "lead" molecule for vitiligo treatment through studies conducted at King's College London.
For the first time, a study evaluated the effect of topical piperine combined with narrowband ultraviolet B (NB-UVB) on vitiligo treatment; in this double-blind clinical trial, 63 patients with facial vitiligo were randomly divided into two groups treated with piperine (case) and placebo (control), both groups also receiving NB-UVB phototherapy every other day for 3 months; in the case group, 10 patients reported a burning sensation on treated skin areas. Consistent with previous research, Piper nigrum and its main alkaloid, piperine, were found to promote melanocyte proliferation in vivo, and pure piperine and a black pepper fruit extract were integrated in two different ointments and tested on human subjects affected by vitiligo.
5.5 Neuroprotection and Cognitive Function
Evidence level: Predominantly preclinical (animal models); no large human RCTs have established efficacy.
Research has turned to natural substances such as piperine, known for its neuroprotective properties, with studies investigating the effects of piperine on cognitive function and genes associated with oxidative stress, inflammation, and necroptosis-related genes. Spatial learning and memory improved significantly in piperine-treated rat groups with no impact on swimming velocity, indicating cognitive enhancement without affecting motor functions in a scopolamine-induced cognitive impairment model. These findings are from animal studies only.
In a temporal lobe epilepsy or post-status-epilepticus animal model, piperine treatment (25 mg/kg for 10 days) restored serotonin levels and modulated MAO and γ-aminobutyric acid (GABA)ergic pathways. In a maximal electroshock-induced seizure model of epilepsy, piperine treatment (10 mg/kg) reduced morbidity by negatively regulating the Na+ channel, delaying the onset of tonic-clonic seizures. Human clinical data in epilepsy are limited, though some clinical trials have yielded promising results confirming piperine's relevance in epilepsy.
5.6 Cancer Chemoprevention
Evidence level: Substantial in vitro and animal preclinical data; human clinical evidence is preliminary and confined largely to combination therapies.
In LNCaP, PC-3, and DU-145 prostate cancer cells, piperine activated caspase-3 and cleaved PARP-1 proteins and reduced the expression of phosphorylated STAT-3 and NF-κB transcription factors. A study showed that piperine (8, 16, and 20 µM) inhibited cell viability and caused apoptosis in human ovarian A2780 cells via the JNK/p38 MAPK-mediated intrinsic apoptotic pathway.
In colorectal adenocarcinoma cells, piperine treatment inhibited cell proliferation in a concentration- and time-dependent manner, as indicated by reduced Ki-67 levels and decreased colony-forming ability; piperine also induced S-phase cell cycle arrest and facilitated apoptosis, evidenced by changes in Bax, Bcl-2, cleaved caspase-3, and cleaved PARP levels.
Although preclinical studies suggest that piperine has potential as an anticancer agent, more comprehensive human clinical trials are necessary to optimize its efficacy and safety as an antitumour treatment; most research has focused on the effects of piperine in combination with other agents such as curcumin. A phase II clinical trial evaluated a combination of piperine, curcumin, and taurine, each at specific concentrations and formulated into a single capsule, administered to patients with hepatocellular carcinoma (HCC). Results of human clinical trials specific to piperine alone as an anticancer agent remain very limited.
5.7 Metabolic and Lipid Effects
Evidence level: Preliminary; mainly animal and combination-supplement human data.
Black pepper contains piperine, which is used to decrease the absorption of cholesterol and improve the movement of cholesterol carrier proteins. In human studies, piperine has demonstrated a variety of pharmacological effects including gastrointestinal stimulation, anti-asthmatic, antioxidant, anti-hyperlipidaemic, anti-diabetic, and anti-inflammatory activities, and enhancement of food absorption.
6. Body Systems and Health Areas
- Gastrointestinal system: Used traditionally to aid digestion, improve appetite, and treat colic and dyspepsia. Piperine modifies gastric emptying and intestinal transit, and enhances nutrient and drug absorption through multiple mechanisms.
- Musculoskeletal system: Well reported in Indian medicine for treatment of rheumatoid arthritis and inflammation. Preclinical evidence supports anti-inflammatory and antinociceptive activity in arthritis models.
- Respiratory system: Long pepper and black pepper are widely used in Siddha, Ayurveda, and Unani systems of medicine particularly for diseases of the respiratory tract.
- Nervous system: Proposed neuroprotective, antidepressant (via MAO inhibition), and anticonvulsant effects; primarily established in preclinical studies.
- Integumentary system (skin): Piperine was found to stimulate the replication of human melanocytes in culture and when grown within a reconstructed skin model.
- Cardiovascular and metabolic system: Proposed antihypertensive, anti-hyperlipidaemic, and anti-diabetic activities documented in preclinical studies and some combination human trials.
- Drug metabolism/pharmacokinetics: Piperine inhibits both the drug transporter P-glycoprotein and the major drug-metabolising enzyme CYP3A4.
7. Dosage Forms and Reported Dosages
The daily consumption of pepper ranges from approximately 83 to 333 mg; consequently, doses of 5 to 20 mg of piperine are often administered daily in clinical trials.
- 3 mg/day (oral): Co-administration with only 3 mg of piperine resulted in doubling blood levels of propranolol without slowing down the drug elimination rate.
- 5 mg/day (oral): Human subjects receiving 2 g curcumin with 5 mg piperine for one week showed increased plasma curcumin levels (2-fold) compared to individuals receiving curcumin alone, measured 2 hours after the last dose.
- 10 mg/day (oral): In a published randomised controlled trial, 1 g curcuminoids per day were co-supplemented with 10 mg/day piperine for eight weeks in subjects with metabolic syndrome.
- 15 mg/day (oral): Pretreatment with 15 mg/day for three consecutive days elevated the AUC0–5h of midazolam by 20% in clinical healthy subjects.
- 20 mg/day (oral): The most commonly studied clinical dose. 2 g of curcumin administered concomitantly with 20 mg of piperine produced a 2,000% increase in curcumin oral bioavailability. Participants were pretreated with 20 mg of piperine daily for seven days in the theophylline and phenytoin interaction study.
- Topical (vitiligo): Topical piperine combined with narrowband UVB phototherapy was evaluated in a double-blind clinical trial of 63 patients with facial vitiligo treated every other day for 3 months.
The average amount of pepper consumed by a person during a day in the United States is approximately 359 mg, which translates to 18–32 mg of piperine per day.
8. Safety Considerations and Drug Interactions
General Safety Profile
Black pepper/piperine is listed under the FDA as being safe (GRAS status); rat trials show a daily intake of 5 to 20 times the average daily human dose produced no clinical symptoms, and studies on acute, subacute, and chronic piperine toxicity show no abnormalities, clinical symptomatology, or significant blood chemistry data in laboratory animals.
In human clinical studies at bioenhancer dosages, piperine enhanced bioavailability with no adverse effects reported. However, piperine's pharmacokinetic limitations—including poor aqueous solubility, rapid metabolism, and low oral bioavailability—pose challenges to its clinical application.
Topical Adverse Effects
In the double-blind vitiligo clinical trial, 10 patients in the piperine case group reported a burning sensation on their treated skin areas (p = 0.002).
Drug–Drug and Food–Drug Interactions via CYP3A4 and P-glycoprotein
Clinical studies suggest that piperine (usually in doses of 20 mg/day) can inhibit CYP3A4, CYP2C9, and P-glycoprotein, resulting in moderate increases in plasma concentrations of CYP3A4 substrates (carbamazepine, midazolam, and possibly others), CYP2C9 substrates (diclofenac, phenytoin, and possibly warfarin and others), and P-glycoprotein substrates (fexofenadine and possibly digoxin and others).
PBPK modelling predicts that following a 7-day intake of 20 mg/day piperine, significant increases in AUC exceeding 1.25 were observed for ritonavir (31%), nifedipine (34%), cyclosporine (35%), triazolam (36%), alfentanil (39%), and simvastatin (59%) in humans.
The dichotomous effects of piperine on induction of CYP3A4 and MDR1 expression (observed in cell studies) and inhibition of their activity (reported elsewhere) challenges the straightforward use of piperine as a bioavailability enhancer and suggests that caution should be taken for piperine consumption during drug treatment, particularly for those who favour daily pepper spice or rely on certain pepper remedies.
Because both P-glycoprotein and CYP3A4 are expressed in enterocytes and hepatocytes and contribute to a major extent to first-pass elimination of many drugs, dietary piperine could affect plasma concentrations of P-glycoprotein and CYP3A4 substrates in humans.
Interaction with Antidepressants and Antiepileptics
Since many standard antidepressants, including SSRIs and tricyclic antidepressants, are extensively metabolised in the liver by CYP450, co-administration with piperine may theoretically elevate the plasma concentration of these drugs, increasing the risk of dose-dependent toxicity.
Potential Interaction with Curcumin's Own Effects
Treatment with curcumin and 40 mg/kg piperine in a streptozotocin-diabetic rat model abrogated the beneficial antidiabetic and antioxidant effects of curcumin. These findings suggest that co-administration of curcumin with a bioenhancer did not bring advantage to curcumin's antidiabetic and antioxidant effects, which could be related to changes in its biotransformation. This animal-model finding highlights that the bioenhancer effect of piperine does not uniformly translate to enhanced pharmacological activity.
Dietary Intake Considerations
It is not clear from available research whether dietary use of black pepper at typical culinary levels would result in clinically significant drug interactions. Most documented interaction risks are associated with supplemental or concentrated piperine doses (≥ 15–20 mg/day) that exceed usual dietary exposure.
References
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