Hyperforin: A Comprehensive Reference
1. Identity and Chemical Characterization
1.1 Names and Classification
Hyperforin is a polyprenylated acylphloroglucinol derivative from Hypericum perforatum (St. John's wort). Its systematic IUPAC name describes a complex bicyclic skeleton: the structure shares the 1-(2-methyl-1-oxopropyl)-2,12-dioxo tricyclic framework, and the molecular formula is C₃₅H₅₂O₄ for hyperforin itself. An oxidation product retaining the same carbon count (C₃₅H₅₂O₅) has also been characterized. Hyperforin is sometimes called "hypericum factor A," and its closely related analogue, adhyperforin, differs in its acyl side chain. Hyperforin and adhyperforin both contribute to the antidepressant effects of Hypericum perforatum, and the involvement of branched-chain amino acids in their biosynthesis has been demonstrated in shoot cultures.
1.2 Molecular Architecture and Unique Structural Properties
Hyperforin is characterized by its phloroglucinol core and multiple prenyl groups, exerting its effects primarily through modulation of synaptic vesicle function and ion channel activity. The underlying mode of action is unique to hyperforin because the compound does not interact directly with the transmitter transporters but elevates the intracellular sodium concentration. Despite its relatively small size, the structure constitutes a thorny synthetic challenge and remains to this day defiant to chemical synthesis.
1.3 Biosynthesis
Enzymatically, the skeleton of hyperforin is formed by isobutyrophenone synthase from isobutyryl-CoA and three molecules of malonyl-CoA. The biosynthesis of hyperforin involves five isoprenoid moieties, which are derived entirely or predominantly (>98%) via the deoxyxylulose phosphate pathway, while the phloroglucinol moiety is generated via a polyketide-type mechanism. The involvement of branched-chain amino acids has been demonstrated in H. perforatum shoot cultures, with L-valine and L-isoleucine being incorporated into the acyl side chains of hyperforin and adhyperforin, respectively.
1.4 Natural Source and Distribution
St. John's wort (H. perforatum), sometimes called perforate St. John's wort or common St. John's wort, is a flowering plant in the family Hypericaceae. It is a hairless, perennial herb with woody roots, yellow flowers marked by black glands, and leaves that appear perforated due to translucent glands. It is the type species of its genus, known for its historical use in folklore and traditional medicine. It is native to much of Europe, West and Central Asia, and parts of Africa and China, and has been widely introduced elsewhere, thriving in well-drained, temperate habitats such as meadows, hillsides, and open woods with moderate rainfall and mild temperatures.
The most common active chemicals in Hypericum perforatum are hypericin and pseudohypericin (naphthodianthrones), and hyperforin (a phloroglucinol derivative). In the wild, the concentrations of any active chemicals can vary widely among individual plants and populations.
1.5 Chemical Stability and Formulation Challenges
Hyperforin is an antibacterial ingredient from St. John's wort that is suitable for the treatment of inflammatory skin diseases. Owing to its pronounced lipophilicity, it is readily soluble only in nonpolar solvents and fats. Upon emulsification in aqueous solutions, rapid degradation of hyperforin occurs. This problem can be avoided by preparing various salts of hyperforin, in which form hyperforin is stable on storage. The clinical applications of hyperforin are limited by the hydrophobic characteristics and the instability of the molecule. Research groups have therefore developed stabilized derivatives and complexes, including cyclodextrin-based formulations, to improve aqueous solubility and photoprotection for topical and systemic use.
1.6 Common Preparations and Dosage Forms
Alcoholic SJW extracts are a mixture of substances with widely varying physical and chemical properties and activities; hyperforin, a phloroglucinol derivative, is the main source of pharmacological effects caused by the consumption of alcoholic extracts of SJW in the therapy of depression. Extracts are also produced using CO₂ supercritical extraction: CO₂ extracts of Hypericum perforatum contain, as active constituents, virtually only hyperforins from the group consisting of the acylphloroglucinols, but virtually no hypericins from the group consisting of the naphthodianthrones. Well-characterized standardized extracts used in clinical trials include LI 160 (standardized to 0.3% hypericin) and WS 5570/WS 5572 (standardized to specific hyperforin content). Readers should note that the benefits documented in clinical trials are only applicable to standardized extracts such as LI 160, WS 5570/2, and ZE 117.
Hyperforin is available in:
- Oral solid dosage forms — film-coated tablets and capsules containing dry hydroalcoholic extracts, standardized to defined percentages of hyperforin (commonly 1–5%).
- Topical preparations — creams and ointments standardized to defined hyperforin concentrations (e.g., 1.5% in clinical studies of atopic dermatitis).
- CO₂ supercritical extracts — enriched in hyperforin, used in dermatological products.
- Cyclodextrin complexes — an experimental stabilized aqueous form for research and topical use.
2. Traditional and Historical Use
2.1 Ancient Greek and Roman Use
The use of Hypericum perforatum as an herbal remedy to treat a variety of internal and external ailments dates back to the time of the ancient Greeks. Since then, it has remained a popular treatment for anxiety, depression, cuts, and burns. In classical herbalism, Dioscorides and Pliny the Elder described its use in healing wounds and burns. The Greeks and Romans were among the first to document the use of St. John's wort, utilizing it for a multitude of ailments, ranging from wounds and burns to melancholy and nervous disorders.
It is important to note that these ancient traditions referred to the whole plant and its preparations, not to the isolated compound hyperforin, which was not chemically identified until the modern era. The phytochemical understanding of hyperforin as an active principle is entirely a product of late 20th-century science.
2.2 Medieval European Traditions
The genus name Hypericum is possibly derived from the Greek words hyper (above) and eikon (picture), in reference to the tradition of hanging the plant over religious icons in the home. The common name "St John's wort" comes from the fact that its flowers and buds were commonly harvested at the time of the Midsummer festival, which was later Christianized as St John's Feast Day on 24 June. It was believed that harvesting the flower at this time made its healing and magical powers more potent. The herb would be hung on house and stall doors on St John's Feast Day to ward off evil spirits and to safeguard against harm and sickness to people and livestock.
As centuries passed, St John's wort continued to weave its way through various cultures and medical traditions. In medieval Europe, it was a staple in monastic gardens, revered not only for its healing properties but also for its supposed mystical powers. From the time of the ancient Greeks down through the Middle Ages, the plant was considered to be imbued with magical powers and was used to ward off evil and protect against disease. As a practical folk remedy, it was used widely to heal wounds, remedy kidney troubles, and alleviate nervous disorders, even insanity.
2.3 19th Century Western Herbal Practice
In the 19th century, Eclectic physicians in the U.S. used St. John's wort for nerve pain, spinal irritation, depression, and trauma recovery. Preparations historically included oil macerations of the flowering tops in olive or other vegetable oils (yielding the distinctive red "Hypericum oil"), alcohol tinctures, and dried herb infusions.
2.4 Summary of Traditional Preparations and Purposes
- Wound healing — oil macerations and poultices applied topically to cuts, burns, and abrasions.
- Mood and nervous conditions — oral preparations (infusions, tinctures) for melancholy, nervous exhaustion, and insanity.
- Kidney and urinary complaints — infusions taken internally in folk medicine.
- Ritual protection — the whole plant hung in homes during midsummer to ward off illness and evil.
Various dosage forms of Hypericum have been used topically as an astringent and to treat injuries or conditions such as blisters, burns, cuts, hemorrhoids, inflammation, insect bites, itching, redness, and sunburns.
3. Key Constituents and Active Compounds of Hypericum perforatum
While hyperforin is the focus of this article, understanding its position within the broader phytochemistry of its source plant is essential.
Chemical investigations into the constituents of H. perforatum have detected seven groups of medicinally active compounds. The most common classes include naphthodianthrones, phloroglucinols, and flavonoids (such as phenylpropanes, flavonol glycosides, and biflavones), as well as essential oils. Two major active constituents have been identified: hypericin (a naphthodianthrone) and hyperforin (a phloroglucinol).
Hyperforin, the phloroglucinol derivative, is the main source of pharmacological effects caused by the consumption of alcoholic extracts of SJW in the therapy of depression. However, several studies indicate that flavone derivatives, e.g. rutin, and also the naphthodianthrones hypericin and pseudohypericin, take part in the antidepressant efficacy.
The phloroglucinol subclass of H. perforatum contains hyperforin as the predominant member, along with adhyperforin, which differs in the structure of its acyl substituent. Hyperforin and adhyperforin both contribute to the antidepressant effects of Hypericum perforatum.
4. Mechanisms of Action
4.1 Broadband Neurotransmitter Reuptake Inhibition
Hyperforin is a broad-band neurotransmitter reuptake inhibitor which affects the synaptosomal uptake of serotonin, dopamine, noradrenaline (norepinephrine), glutamate and gamma-aminobutyric acid (GABA) with similar efficiencies. This profile distinguishes it sharply from conventional antidepressants: many antidepressant drugs behave as more or less selective inhibitors for the reuptake of one or more neurotransmitters (mainly, serotonin), acting as competitive inhibitors at the transmitter binding sites of the transporter proteins involved in this reuptake. Hyperforin is exceptional, showing a wide range of inhibitory effects affecting the reuptake of serotonin, dopamine and noradrenaline, but also those of GABA and glutamate. This wide range of effects points to a completely new mechanism of action for hyperforin.
4.2 Indirect Mechanism: Ion Gradient Disruption
Crucially, hyperforin does not inhibit reuptake transporters directly. Unlike other synthetic antidepressant drugs, (+)-hyperforin follows a completely new and different mechanism of action. The compound acts as a broadband neurotransmitter reuptake inhibitor that affects the synaptosomal uptake of serotonin (5-HT), dopamine (DA), noradrenaline (norepinephrine), glutamate, and γ-aminobutyric acid (GABA) with similar potencies. (+)-Hyperforin is the only molecule reported so far to act in this nonselective manner, not involving the inhibition of neurotransmitter transporter proteins, but activating the TRPC6 receptor to induce the entry of Ca²⁺ and Na⁺ into the cell, thereby inhibiting the gradient-driven neurotransmitter reuptake.
The different transport proteins involved in neurotransmitter reuptake have a common point: all of them make use of the sodium gradient as their driving force. Hyperforin has been shown to reduce this gradient by the activation of a sodium conductivity mechanism, most likely involving ionic channels.
4.3 TRPC6 Ion Channel Activation
Hyperforin does not activate other closely related TRPC channels such as TRPC3 and TRPC7, strongly suggesting that hyperforin is a selective activator of TRPC6. Research has demonstrated in several in vitro neuronal models that the activation of TRPC6 functions as a protonophore, causing cytosolic acidification, which fuels the plasma membrane sodium–proton exchanger. These effects lead to an increase in the free intracellular sodium concentration and inhibit neurotransmitter uptake via Na⁺ cotransport.
Hyperforin exerts its effects primarily through modulation of synaptic vesicle function and ion channel activity. It non-selectively inhibits the reuptake of several neurotransmitters, including serotonin, dopamine, and norepinephrine, through a mechanism involving transient receptor potential (TRP) channels. This broad-spectrum inhibition can lead to significant changes in synaptic plasticity and neurotransmission, impacting mood regulation, anxiety, and cognition.
4.4 Additional Receptor and Signaling Effects
In addition, hyperforin inhibits the responses mediated by GABA, NMDA and AMPA receptors, and promotes the opening of presynaptic calcium channels, leading to a release of neurotransmitters to the intersynaptic space.
Hydroalcoholic hypericum extract inhibits the synaptosomal uptake of serotonin, norepinephrine, and dopamine with about similar affinities and leads to a significant down-regulation of cortical beta-adrenoceptors and 5-HT₂-receptors after subchronic treatment of rats. While neither hypericin nor kaempferol showed any reuptake inhibiting properties, hyperforin was identified as the unspecific reuptake inhibitor of hypericum extracts, with half-maximal inhibitory concentrations for the three synaptosomal uptake systems between 80 and 200 nmol/L. Moreover, a hyperforin-enriched (38%) CO₂ extract also leads to a significant beta-receptor down-regulation after subchronic treatment. The data suggest hyperforin as the active principle of hypericum extracts in biochemical models of antidepressant activity.
4.5 Pregnane X Receptor (PXR) Activation and Drug Metabolism Induction
A mechanistically distinct and clinically very significant action of hyperforin is its role as a potent PXR ligand. Hyperforin, the principal mediator of St. John's wort antidepressive action, is also the main reason for St. John's wort herbal drug interaction potential. Hyperforin is a good ligand for the pregnane xenobiotic receptor (PXR) and thus acts as a potent inducer of CYP3A4 and P-gp, the gene product of MDR1. Testing the influence of in vitro treatment with hyperforin on the mRNA expression in human hepatocytes revealed significantly enhanced expression of CYP2B6, CYP2C9, CYP3A4, CYP3A5, UGT1A1, and ABCB1.
4.6 Anti-inflammatory Mechanisms
Hyperforin, the main component responsible for the antidepressant action of Hypericum perforatum, displays additional beneficial properties including anti-inflammatory, antimicrobic, and antitumor activities. One of the major constituents of H. perforatum, hyperforin, helps to reduce transepidermal water loss by differentiating keratinocytes and protects the skin barrier with this mechanism.
4.7 Anticancer Mechanisms (Preclinical)
These natural compounds have a remarkable potential for both prophylactic and therapeutic use against tumor development by mechanisms that involve modulation of ROS production and action along different steps of carcinogenesis, as well as regulation of proton dynamics in cancer cells. Hyperforin also blocks tumor cell growth by inducing mitochondrial permeabilization-triggered apoptosis.
5. Scientific Evidence by Area of Use
5.1 Major Depressive Disorder (MDD) and Mild-to-Moderate Depression
Evidence Summary
This is the best-studied area for hyperforin-containing Hypericum extracts, with multiple randomized controlled trials (RCTs) and several systematic reviews and meta-analyses available.
Systematic Reviews and Meta-Analyses
Thirty-five studies examining 6,993 patients met inclusion criteria in a 2016 systematic review; eight studies evaluated a hypericum extract that combined 0.3% hypericin and 1–4% hyperforin. The herb SJW was associated with more treatment responders than placebo (relative risk [RR] 1.53; 95% CI 1.19–1.97; I² 79%; 18 RCTs; N = 2,922, moderate quality of evidence; standardized mean differences [SMD] 0.49; CI 0.23–0.74; 16 RCTs; I² 89%; N = 2,888, moderate quality of evidence).
A Cochrane Review of SJW for depression documented available research published to 2008 and found a beneficial effect compared to both placebo and other antidepressant therapies across 29 double-blind RCTs. The review concluded that the available evidence suggested that hypericum extracts tested in the included trials are superior to placebo in patients with major depression and are similarly effective as standard antidepressants, and have fewer side effects than standard antidepressants.
A meta-analysis reviewing 27 clinical trials with a total of 3,808 patients comparing the use of St. John's wort and SSRIs found that in patients with depression, St. John's wort demonstrated comparable response (pooled RR 0.983, 95% CI 0.924–1.042) and remission (pooled RR 1.013, 95% CI 0.892–1.134) rates, and a significantly lower discontinuation/dropout rate (pooled OR 0.587, 95% CI 0.478–0.697) compared to standard SSRIs.
A meta-analysis of 37 double-blind RCTs that compared clinical effects of Hypericum monopreparation with either placebo or a standard antidepressant in adults with depressive disorders found that larger placebo-controlled trials restricted to patients with major depression showed only minor effects over placebo, while older and smaller trials not restricted to patients with major depression showed marked effects. This heterogeneity in findings — with clearer benefits in mild-to-moderate depression and less certain benefits in severe MDD — is a persistent feature of the literature.
The Role of Hyperforin Content Specifically
For a long time hypericin was assumed to be the main active principle in Hypericum extracts. However, studies found that the phloroglucinol derivative hyperforin mostly accounts for the antidepressant effect rather than hypericin.
The clinical significance of hyperforin content was directly tested in the WS 5570/WS 5572 series of extracts. Hypericum perforatum extract WS® 5570 at doses of 600 mg/day (once daily) and 1,200 mg/day (600 mg twice daily) were found to be safe and more effective than placebo, with comparable efficacy of the WS® 5570 groups for the treatment of mild to moderate major depression.
Limitations
A 2009 Cochrane systematic review of 29 international studies suggested that St. John's wort may be better than a placebo and as effective as standard prescription antidepressants for major depression of mild to moderate severity. It is uncertain whether this is true for severe depression and for time periods longer than 12 weeks. In addition, preparations of SJW vary in the amounts of active compounds they contain, which may make it difficult to compare across studies. The high heterogeneity in meta-analyses (I² values up to 89%) further limits definitive conclusions.
Evidence strength for mild-to-moderate depression: Moderate. Multiple large RCTs and systematic reviews support efficacy comparable to SSRIs with a more favorable side-effect profile. For severe MDD, evidence is weak and inconsistent.
5.2 Atopic Dermatitis and Skin Inflammation (Topical Use)
Recent investigations suggest an anti-inflammatory and antibacterial effect of hyperforin. In a half-side comparison study, the efficacy of a cream containing Hypericum extract standardized to 1.5% hyperforin (verum) was assessed in comparison to the corresponding vehicle (placebo) for the treatment of subacute atopic dermatitis. The study design was a prospective, randomized, placebo-controlled, double-blind monocentric study. In 21 patients suffering from mild to moderate atopic dermatitis (mean SCORAD 44.5), the treatment with verum or placebo was randomly allocated to the left or right site of the body, respectively. The patients were treated twice daily over a period of four weeks. Topical treatment of mild atopic dermatitis with a cream containing 1.5% HP extract was significantly superior to the vehicle.
The lipophilic phloroglucin derivative hyperforin displays antibacterial, anti-inflammatory, and keratinocyte differentiation-promoting properties. Several clinical studies have been performed testing the effects of H. perforatum in atopic dermatitis treatment, wound healing after caesarean section and episiotomy, as well as healing of post-surgical scalp wounds, bed sores, and venous ulcers.
Evidence strength: Preliminary to moderate. The atopic dermatitis RCT was small (N=21) but well designed. Other topical applications (wound healing, burns, scar treatment) have been investigated in small clinical studies with largely positive but not definitive results. Larger confirmatory trials are lacking.
5.3 Antibacterial Activity
Hyperforin exhibits antidepressant activity by a novel mechanism of action, antibiotic activity against gram-positive bacteria, and antitumoral activity in vivo. Hyperforin has antimicrobial activity against microorganisms such as Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. The sole antibacterial principle isolated to date from Hypericum is a tetraketone, hyperforin, also thought to be responsible for the antidepressant activity of the herb.
Among synthetic derivatives of hyperforin, octahydrohyperforin also possesses antibacterial activity against both the planktonic and biofilm states of bacteria.
Evidence strength: Primarily preclinical (in vitro). The antibacterial effects are well-documented in laboratory settings and partially underpin traditional topical wound-healing use, but controlled clinical trials specifically targeting bacterial infection with isolated hyperforin are lacking.
5.4 Anticancer Activity
Hyperforin has been investigated in preclinical oncology research across numerous cancer types. Hyperforin displays additional beneficial properties including anti-inflammatory, antimicrobic, and antitumor activities, though its activity on melanoma is poorly documented. Investigation of HPF's antimelanoma effectiveness in A375, FO1, and SK-Mel-28 human BRAF-mutated cell lines found that all melanoma cells were affected by low HPF concentrations (EC₅₀ 2–4 µM) in a time-dependent manner.
HF has been identified as the major molecule responsible for the anti-depressant effects of this plant, and its neurobiological effects include neurotransmitter re-uptake inhibition, the ability to increase intracellular sodium and calcium levels, canonical transient receptor potential activation, and N-methyl-D-aspartic acid receptor antagonism. The natural phloroglucinol hyperforin also displays anti-inflammatory and anti-tumoral properties of potential pharmacological interest.
Although further studies are undoubtedly required for a full clarification of mechanisms and effects, ample experimental evidence in vitro and in vivo already points out that SJW and HPF can play a remarkable role as nutraceutical supplement or in association with chemotherapy in the challenging fight against cancer. Hyperforin displays antibacterial, antiproliferant, and antiangiogenic activity. Synthetic derivatives of hyperforin have also recently been reported to possess increased bioactivity.
Evidence strength: Preclinical only. All anticancer evidence is in vitro or in animal models. No human clinical trials have been published evaluating hyperforin as an anticancer agent. The preclinical data are mechanistically interesting, particularly regarding apoptosis induction and antiangiogenic effects, but cannot be extrapolated to clinical recommendations.
5.5 Anxiety
Hyperforin may be a constituent responsible for the antidepressant and anxiolytic properties of extracts of St. John's wort. Since ancient times, the plant has remained a popular treatment for anxiety, depression, cuts, and burns. However, dedicated clinical trials specifically isolating the anxiolytic effect of hyperforin (as opposed to hypericin or whole extracts) are sparse. The anxiolytic signal in the published literature largely derives from RCTs primarily designed to assess depression outcomes, in which anxiety subscales showed improvement alongside mood outcomes.
Evidence strength: Weak to moderate. Clinical evidence for anxiety is largely secondary to depression trials; head-to-head anxiolytic trials using hyperforin-standardized extracts specifically for anxiety disorders are lacking.
5.6 Neuroprotection
Recent research suggests the effectiveness of Hypericum perforatum in treating cancer, inflammation-related disorders, and bacterial and viral diseases, and as an antioxidant and neuroprotective agent. Hyperforin regulates the expressions of genes related to depressive states. Neuroprotective effects have been described at the preclinical level, including effects on neuroplasticity and neurogenesis through the TRPC6 pathway. Increased neuronal activity may influence the release of neurotransmitters like serotonin and dopamine, which are known to play a crucial role in mood regulation. Additionally, this activity could impact neuroplasticity, which is thought to be impaired in depression.
Evidence strength: Primarily preclinical. No robust human clinical trials specifically evaluating neuroprotective outcomes with hyperforin have been published.
6. Pharmacokinetics
6.1 Oral Absorption and Peak Plasma Levels
Some pharmacokinetic data on hyperforin are available for an extract containing 5% hyperforin. Maximal plasma levels (Cmax) in human volunteers were reached 3–4 hours after administration of an extract containing 14.8 mg hyperforin. Biological half-life (t½) and mean residence time were 9 hours and 12 hours, respectively, with an estimated steady-state plasma concentration of 100 ng/mL (approximately 180 nM) for 3 doses per day. Linear plasma concentrations were observed within a normal dosage range and no accumulation occurred.
A separate clinical pharmacokinetic study using a higher-dose regimen produced different half-life values: an oral dose of 900 mg of a proprietary St. John's wort extract containing 18 mg hyperforin in healthy volunteers produced a mean Cmax of 122 ng/mL after 4.5 h, and the half-life of this constituent was approximately 18 h. In healthy male volunteers, 612 mg dry extract of St. John's wort produced hyperforin pharmacokinetics characterized by a half-life of 19.64 hours.
6.2 Dose-Dependent Interactions
Hypericum extract with hyperforin 41 mg in the daily dose decreased midazolam bioavailability by about 80%, more than an extract with hyperforin 12 mg/day (decrease by about 50%) or extract with hyperforin 0.13 mg/day (decrease by about 20%). Extract with hyperforin 0.06 mg/day decreased the bioavailability by only 11%. Renal transplant recipients receiving a St. John's wort extract with a 7-mg daily dose of hyperforin had a 45% lower ciclosporin bioavailability than those recipients taking extract with hyperforin 0.45 mg/day.
6.3 Bioavailability Across the Literature
These findings highlight that key constituents of St. John's wort are bioavailable and achieve adequate concentrations in human plasma after oral dosing. In contrast to the amount of documentation concerning clinical efficacy, oral bioavailability and pharmacokinetic data about the active components are rather scarce.
7. Dosages Reported in Studies
The following dosages come directly from peer-reviewed sources and do not represent recommendations.
- WS® 5570 extract, depression: 600 mg/day (once daily) and 1,200 mg/day (600 mg twice daily) were found safe and more effective than placebo for mild to moderate major depression.
- Clinical studies in systematic reviews: Eight studies evaluated a hypericum extract combined 0.3% hypericin and 1–4% hyperforin.
- Pharmacokinetic study: Film-coated tablets containing 300 mg hypericum extracts representing 14.8 mg hyperforin were used in healthy volunteer studies.
- Topical atopic dermatitis: A cream containing Hypericum extract standardized to 1.5% hyperforin, applied twice daily over a period of four weeks in 21 patients.
- Co-administration studies (SSRI combinations): St. John's wort dosages typically ranged between 600 mg and 900 mg per day in studies documenting serotonin syndrome risk.
- Low-dose hyperforin preparations: Products with a daily dose of <1 mg hyperforin were less likely to be associated with major interactions for drugs that are CYP3A4 or P-glycoprotein substrates.
8. Body Systems and Health Areas Associated with Hyperforin
- Central Nervous System: Antidepressant activity (serotonin, dopamine, norepinephrine, GABA, glutamate reuptake inhibition via TRPC6/sodium gradient); anxiolytic properties; possible neuroprotective effects through neuroplasticity modulation.
- Skin and Integument: Anti-inflammatory and antibacterial effects applied topically; keratinocyte differentiation; wound healing; atopic dermatitis improvement.
- Hepatic and Gastrointestinal Metabolism: PXR-mediated CYP3A4, CYP2C9, CYP2B6 and P-glycoprotein induction, significantly altering the metabolism of co-administered drugs.
- Immune System / Oncology (preclinical): Pro-apoptotic effects in cancer cell lines; anti-inflammatory signaling modulation; antiangiogenic properties at the preclinical level.
- Antimicrobial: Activity against gram-positive and select gram-negative bacteria in vitro.
9. Safety, Adverse Effects, and Drug Interactions
9.1 General Tolerability
All the recent clinical trials mentioned in the literature suggest that Hypericum is more tolerable than synthetic antidepressants as it causes fewer side effects and also shows similar adverse reactions as seen in placebo-controlled groups. Other side effects of St. John's wort are usually minor and uncommon and may include upset stomach and sensitivity to sunlight.
9.2 Photosensitivity
Overall, SJW has been considered safe but side effects have been noted, including photosensitivity, elevated thyroid-stimulating hormones, hypertensive crisis, and induction of mania. Photosensitivity has been primarily attributed to hypericin rather than hyperforin; however, products containing significant hypericin alongside hyperforin contribute to this risk.
9.3 Pharmacodynamic Interactions: Serotonin Syndrome
Combining St. John's wort and certain antidepressants can lead to serotonin syndrome, with dangerous symptoms ranging from tremor and diarrhea to very dangerous confusion, muscle stiffness, drop in body temperature, and even death. SSRIs such as citalopram, escitalopram, and sertraline, metabolized by CYP2C19, are more likely to interact with St. John's wort than those metabolized by CYP2D6, such as paroxetine, fluoxetine, and fluvoxamine. The most significant adverse effect observed was serotonin syndrome, with case studies highlighting sertraline and paroxetine as the most commonly involved SSRIs.
9.4 Pharmacokinetic Interactions via PXR/CYP3A4/P-gp Induction
A number of clinically significant interactions have been identified with prescribed medicines including warfarin, phenprocoumon, cyclosporin, HIV protease inhibitors, theophylline, digoxin, and oral contraceptives, resulting in a decrease in concentration or effect of the medicines.
Hyperforin contained in hypericum extracts binds to pregnane X receptor (PXR), after which CYP3A4 as well as P-gp are induced in the liver, intestine, and other organs. Less pronounced and not yet fully accepted are findings that hyperforin also substantially induces CYP1A2, CYP2C9, and CYP2C19. Induction of CYP3A4 and P-gp may occur as early as 3 days of treatment. It reaches a maximum after approximately 1–2 weeks, although it can still be observed for a similarly long period after interruption of treatment and is reversible. This circumstance must therefore be taken into account when switching from a hyperforin-rich to a hyperforin-poor preparation.
Pharmacokinetic interactions with CYP3A4-metabolized and/or P-gp-transported drugs were reported in cases of acute heart transplant and liver rejection in cyclosporine-treated patients.
Hyperforin is able to induce both CYP3A4, CYP2B6, and P-gp. The induction of both intestinal and hepatic CYP3A4 and drug transporter P-gp is due to the activation of the pregnane X receptor and the subsequent expression of a range of genes. Since cyclosporine (CyA) is metabolized via CYP3A4 and P-gp, SJW may alter CyA bioavailability.
9.5 Hyperforin Content as the Determinant of Interaction Risk
The active substance is hyperforin, the most potent known activator of PXR. Clinical studies have demonstrated that products containing less than 1% hyperforin are less likely to produce interactions. However, most products contain 3% hyperforin. Products that had a daily dose of <1 mg hyperforin were less likely to be associated with major interaction for drugs that were CYP3A4 or P-glycoprotein substrates. Although a risk of interactions cannot be excluded even for low-dose hyperforin preparations.
9.6 Psychiatric Risks
St. John's wort may worsen feelings of anxiety in some people. A rare, but possible side effect is psychosis. Those with certain mental health disorders, such as bipolar disorder, are at risk of experiencing this rare side effect.
9.7 Documented Drug Interactions Summary
- Clinically significant interactions between St. John's wort and the immunosuppressant drug cyclosporine, the antiretroviral agent indinavir, oral contraceptives, warfarin, digoxin, and benzodiazepines have been documented.
- SSRIs and serotonergic agents: Serotonin syndrome risk (pharmacodynamic interaction, as above).
- Antiretrovirals (HIV protease inhibitors): Reduced plasma levels via CYP3A4 induction, risking treatment failure and viral resistance.
- Immunosuppressants (cyclosporine): Reduced cyclosporine plasma levels, with documented cases of acute organ transplant rejection.
- Anticoagulants (warfarin): Reduced anticoagulant effect via accelerated metabolism.
- Oral contraceptives: Reduced hormonal contraceptive efficacy, increasing the risk of unintended pregnancy.
- Digoxin and theophylline: Reduced plasma levels via P-gp induction and/or CYP metabolism.
9.8 Chemical Instability as a Safety Consideration
Hyperforin shows several shortcomings such as poor chemical stability and the induction of drug-drug interactions as a lead compound for further developments. These issues have prompted the synthesis and investigation of chemically simplified and stable hyperforin analogues sharing the phloroglucinol core.
10. Ongoing Research and Synthetic Derivatives
The dual liability of hyperforin — its chemical instability and its potent PXR-activating, drug-interaction profile — has driven medicinal chemistry efforts to create analogues that retain TRPC6 activation while eliminating PXR agonism. One such analogue, Hyp13, shares all features with hyperforin. It activates TRPC6 with similar potency, shows no effect on TRPC3, and binds to the identified binding motif LLKL. Furthermore, Hyp13 in contrast to hyperforin does neither activate PXR nor induce CYP3A4.
The clinical applications of hyperforin are limited by the hydrophobic characteristics and the instability of the molecule. Derivatives of hyperforin including aristoforin, tetrahydrohyperforin, and octahydrohyperforin have demonstrated promising antitumor activity. Among these, octahydrohyperforin also possesses antibacterial activity against both the planktonic and biofilm states of bacteria.
Hyperforin was most frequently related to in vitro cell-protection, anticancer, antidiabetic, and antidepressant activities in a broad review of biological activities across the Hypericum genus, suggesting active areas of pharmacological research beyond its established use in depression.
References
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