Hispidulin

• Neuroprotective
• Anxiolytic
• Anti-inflammatory
• Anticancer

• Anticonvulsant
• Antioxidant
• Antidiabetic
• Hepatoprotective
• Cardiovascular protection

Hispidulin (4′,5,7-trihydroxy-6-methoxyflavone) exerts its diverse biological effects through multiple molecular pathways, with particularly notable activity in the central nervous system. One of hispidulin’s most distinctive and well-studied mechanisms is its interaction with the gamma-aminobutyric acid type A (GABAA) receptor complex. Hispidulin acts as a positive allosteric modulator of GABAA receptors, binding to the benzodiazepine site but with a unique binding profile compared to classical benzodiazepines. This interaction enhances the effect of GABA, the primary inhibitory neurotransmitter in the brain, by increasing chloride ion influx into neurons, resulting in hyperpolarization and reduced neuronal excitability.

This mechanism underlies hispidulin’s anxiolytic and anticonvulsant properties. Interestingly, hispidulin shows some selectivity for GABAA receptor subtypes, which may contribute to its more favorable side effect profile compared to classical benzodiazepines, with potentially less sedation and lower risk of dependence. In addition to its GABAergic effects, hispidulin demonstrates significant neuroprotective properties through multiple mechanisms. It inhibits glutamate-induced excitotoxicity by modulating N-methyl-D-aspartate (NMDA) receptor activity and reducing calcium influx into neurons.

Hispidulin also activates the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which promotes neuronal survival and inhibits apoptosis. Furthermore, it enhances the expression of brain-derived neurotrophic factor (BDNF), supporting neuronal growth, differentiation, and synaptic plasticity. As an anti-inflammatory agent, hispidulin inhibits the nuclear factor-kappa B (NF-κB) signaling pathway by preventing IκB kinase (IKK) activation and subsequent nuclear translocation of NF-κB, thereby reducing the expression of pro-inflammatory genes. It suppresses the production of inflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), while inhibiting cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression.

Hispidulin also modulates the mitogen-activated protein kinase (MAPK) pathway, including p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), further contributing to its anti-inflammatory properties. The antioxidant properties of hispidulin are mediated through both direct and indirect mechanisms. With its three hydroxyl groups, hispidulin can directly scavenge reactive oxygen species (ROS) and free radicals. More significantly, hispidulin activates the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, leading to increased expression of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and heme oxygenase-1 (HO-1).

In cancer cells, hispidulin demonstrates multiple anticancer mechanisms. It induces apoptosis through both intrinsic (mitochondrial) and extrinsic (death receptor) pathways by modulating the expression of Bcl-2 family proteins, activating caspases, and promoting cytochrome c release. Hispidulin inhibits cancer cell proliferation by arresting the cell cycle at G1 or G2/M phases through regulation of cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors such as p21 and p27. It also suppresses cancer cell migration and invasion by inhibiting matrix metalloproteinases (MMPs) and epithelial-mesenchymal transition (EMT).

A particularly significant anticancer mechanism of hispidulin is its ability to inhibit the PI3K/Akt/mTOR signaling pathway, which is frequently dysregulated in various cancers and plays a crucial role in cell proliferation, survival, and metabolism. In metabolic regulation, hispidulin improves insulin sensitivity and glucose metabolism through multiple mechanisms. It enhances glucagon-like peptide-1 (GLP-1) secretion from intestinal L-cells by activating the G protein-coupled receptor 119 (GPR119) and the cAMP/PKA signaling pathway. GLP-1 is an incretin hormone that stimulates insulin secretion, inhibits glucagon release, and improves pancreatic β-cell function.

Hispidulin also activates AMP-activated protein kinase (AMPK), which enhances glucose uptake in skeletal muscle and reduces hepatic glucose production. The balanced hydroxyl/methoxy structure of hispidulin (three hydroxyl groups and one methoxy group) contributes to its unique pharmacological profile. The methoxy group at the 6-position enhances its lipophilicity and membrane permeability, while the hydroxyl groups maintain significant antioxidant capacity. This structural feature also influences its interaction with the GABAA receptor and other molecular targets, contributing to its diverse biological activities.

Optimal dosage ranges for hispidulin in humans have not been well established through clinical trials. Most research has focused on hispidulin as a component of herbal extracts, particularly from Artemisia and Salvia species, rather than as an isolated compound. Based on preclinical studies and limited human research with related compounds, estimated effective doses would range from 5-30 mg of hispidulin daily. It’s important to note that hispidulin’s potent activity at GABAA receptors suggests that its effective dose may be lower than many other flavonoids.

In preclinical studies, hispidulin has shown significant effects at nanomolar to low micromolar concentrations, particularly for its anxiolytic and neuroprotective properties.

Hispidulin has moderate oral bioavailability, estimated at approximately 15-25% in animal studies. This is higher than many highly hydroxylated flavonoids due to its balanced hydroxyl/methoxy structure, which provides a good compromise between water solubility and lipophilicity. The methoxy group at the 6-position increases lipophilicity compared to more hydroxylated flavones, potentially enhancing passive diffusion across cell membranes. However, hispidulin’s bioavailability is still limited by several factors, including first-pass metabolism in the liver, efflux by P-glycoprotein transporters in the intestine, and phase II metabolism (primarily glucuronidation and sulfation).

Interestingly, hispidulin’s ability to cross the blood-brain barrier is relatively good compared to many other flavonoids, which is crucial for its central nervous system effects. This enhanced brain penetration is likely due to its balanced hydroxyl/methoxy structure and relatively small molecular size. In animal studies, hispidulin has been detected in brain tissue after oral administration, supporting its ability to reach its target sites in the central nervous system.

Nanoemulsion formulations – can increase bioavailability by 3-10 fold by improving solubility and enhancing intestinal permeability, Liposomal encapsulation – protects hispidulin from degradation and enhances cellular uptake, particularly beneficial for targeting the central nervous system, Self-emulsifying drug delivery systems (SEDDS) – improve dissolution and absorption in the gastrointestinal tract, Phospholipid complexes – enhance lipid solubility and membrane permeability, Microemulsions – provide a stable delivery system with enhanced solubility, Combination with piperine – inhibits P-glycoprotein efflux and intestinal metabolism, Cyclodextrin inclusion complexes – improve aqueous solubility while maintaining stability, Solid dispersion techniques – enhance dissolution rate and solubility, Co-administration with other flavonoids that may compete for metabolic enzymes, potentially extending hispidulin’s half-life, Intranasal delivery systems – bypass the blood-brain barrier for direct central nervous system effects (experimental)

Hispidulin is best absorbed when taken with meals containing some fat, which can enhance solubility and stimulate bile secretion, improving dissolution and absorption. The presence of other flavonoids may enhance hispidulin’s bioavailability through competitive inhibition of metabolic enzymes or transporters. For anxiolytic effects, taking hispidulin 30-60 minutes before stressful situations may be beneficial due to its relatively rapid onset of action at GABAA receptors. For sleep support, taking hispidulin 30-60 minutes before bedtime may help promote relaxation and sleep onset.

For neuroprotective and anti-inflammatory effects, consistent daily dosing is more important than specific timing, though divided doses throughout the day may maintain more consistent blood levels due to hispidulin’s relatively short half-life (approximately 2-4 hours in animal studies). For metabolic support, taking hispidulin before meals may enhance its effects on GLP-1 secretion and postprandial glucose levels. Enhanced delivery formulations like nanoemulsions or liposomes may have different optimal timing recommendations based on their specific pharmacokinetic profiles, but generally follow the same principles of taking with food for optimal absorption. It’s worth noting that hispidulin’s interaction with GABAA receptors suggests potential for additive effects with alcohol, benzodiazepines, and other GABAergic substances.

Therefore, spacing hispidulin supplementation at least 2-3 hours apart from these substances may help minimize potential interactions.

• Mild sedation or drowsiness (due to GABAA receptor modulation)
• Dizziness (uncommon)
• Gastrointestinal discomfort (mild to moderate)
• Nausea (uncommon)
• Headache (rare)
• Dry mouth (uncommon)
• Fatigue (uncommon)
• Potential for cognitive impairment at higher doses (due to GABAergic effects)
• Allergic reactions (rare)

• Pregnancy and breastfeeding (due to insufficient safety data and potential GABAergic effects on fetal development)
• Individuals with severe hepatic impairment (due to potential altered metabolism)
• Individuals with known hypersensitivity to hispidulin or related flavonoids
• Individuals with a history of substance abuse (due to potential for mild dependence with long-term use)
• Scheduled surgery (discontinue 2 weeks before due to potential sedative effects and interactions with anesthetics)
• Individuals taking medications metabolized by CYP enzymes (due to potential interactions)
• Individuals with severe respiratory conditions (due to potential respiratory depressant effects at high doses)

• Benzodiazepines and other GABAA receptor modulators (additive effects, potentially leading to excessive sedation and respiratory depression)
• Alcohol (additive CNS depressant effects)
• Opioid analgesics (additive CNS depressant effects)
• Anticonvulsant medications (potential for additive effects or interference with therapeutic management)
• Antidepressants, particularly SSRIs and SNRIs (potential for increased risk of sedation and other side effects)
• Sedating antihistamines (additive sedative effects)
• Muscle relaxants (additive muscle relaxant effects)
• Cytochrome P450 substrates (hispidulin may affect the metabolism of drugs that are substrates for CYP enzymes)
• Antidiabetic medications (may enhance blood glucose-lowering effects)
• Drugs requiring high alertness for safe use (hispidulin’s sedative effects may impair performance)

Due to limited human clinical data on isolated hispidulin, a definitive upper limit has not been established. Based on preclinical studies and its activity at GABAA receptors, doses exceeding 30 mg of isolated hispidulin daily are not recommended without medical supervision. For herbal extracts containing hispidulin, doses exceeding 800 mg of standardized extract daily should be approached with caution. It’s important to note that hispidulin’s activity at GABAA receptors suggests potential for tolerance and mild dependence with long-term use at higher doses, similar to but likely less pronounced than classical benzodiazepines.

Therefore, cycling use (e.g., 3-4 weeks on, 1 week off) may be advisable for long-term supplementation, particularly at higher doses. Additionally, abrupt discontinuation after prolonged use of higher doses may potentially lead to mild withdrawal symptoms, so gradual dose reduction is recommended.

Hispidulin itself is not approved as a drug by the FDA and is not commonly available as an isolated supplement. Plant extracts containing hispidulin, such as Artemisia or Salvia extracts, are regulated as dietary supplements under the Dietary Supplement Health and Education Act (DSHEA) of 1994. Manufacturers cannot make specific disease treatment claims but may make general structure/function claims with appropriate disclaimers. The FDA has not evaluated the safety or efficacy of hispidulin specifically.

Due to hispidulin’s activity at GABAA receptors, there is potential for future regulatory scrutiny, particularly if marketed with claims related to anxiety or sleep, as these effects are pharmacologically similar to regulated benzodiazepines, albeit likely less potent.

Eu: In the European Union, hispidulin is not approved as a medicinal product. Plant extracts containing hispidulin may be sold as food supplements, subject to the general food safety regulations. The European Food Safety Authority (EFSA) has not issued specific health claims for hispidulin. Some EU member states may have their own regulations regarding traditional herbal medicinal products containing Artemisia or Salvia species, which may contain hispidulin.

Germany: In Germany, certain Salvia species are approved by Commission E (the German regulatory authority for herbs) for mild gastrointestinal complaints and excessive sweating. However, these approvals are not specifically related to the hispidulin content.

China: In China, various Artemisia species containing hispidulin are officially listed in the Chinese Pharmacopoeia as traditional Chinese medicines. They are approved for specific indications based on traditional use and modern research. Hispidulin as an isolated compound is primarily used in research rather than as an approved therapeutic agent.

Japan: Plant sources of hispidulin are included in various traditional Japanese medicine (Kampo) formulations. Hispidulin as an isolated compound is not specifically regulated for therapeutic use.

Australia: The Therapeutic Goods Administration (TGA) regulates plant extracts containing hispidulin as complementary medicines. Several products containing these extracts are listed on the Australian Register of Therapeutic Goods (ARTG). Traditional use claims are permitted with appropriate evidence of traditional use. Hispidulin as an isolated compound is not specifically regulated.

Canada: Health Canada regulates plant extracts containing hispidulin as Natural Health Products (NHPs). Several products containing these extracts have been issued Natural Product Numbers (NPNs), allowing them to be sold with specific health claims related to traditional use. Isolated hispidulin is not specifically approved as a standalone ingredient.

Medium to high

Isolated hispidulin is rarely available commercially for supplementation and is primarily sold as a research chemical at prices ranging from $300-$800 per 10-25 mg, making

it prohibitively expensive for regular supplementation. Standardized herbal extracts containing hispidulin, such as Artemisia or Salvia extracts, typically cost $0.50-$2.00 per day for basic extracts and $2.00-$5.00 per day for premium, highly standardized formulations. Enhanced delivery formulations such as nanoemulsions or liposomes generally cost $3.00-$8.00 per day.

The cost-effectiveness of hispidulin must be evaluated in the context of herbal extracts containing it, as isolated hispidulin is not practically available for regular supplementation due to its high cost and limited commercial availability. For anxiety and stress management, herbal extracts containing hispidulin offer moderate value compared to conventional anxiolytics. While they may be more expensive than generic benzodiazepines, they potentially offer a more favorable side effect profile with less risk of dependence and cognitive impairment. However, their efficacy may also be less consistent and potent.

For neuroprotective effects, the value proposition is less clear due to limited clinical evidence, though preclinical data is promising. The long-term benefits for neurodegenerative conditions would need to be substantial to justify ongoing supplementation costs. For anticonvulsant effects, herbal extracts containing hispidulin should only be considered as adjunctive therapy under medical supervision, not as a replacement for conventional anticonvulsants. In this context, they may offer value by potentially allowing lower doses of conventional medications, but this approach requires careful medical management.

For general antioxidant and anti-inflammatory benefits, there are likely more cost-effective options than hispidulin-containing extracts, as many other botanical antioxidants have stronger clinical evidence and lower costs. When comparing the cost-effectiveness of herbal extracts containing hispidulin to other supplements with similar indications: For anxiety, hispidulin-containing extracts are generally more expensive than common anxiolytic herbs like valerian or passionflower, but may offer unique benefits through their specific GABAA receptor modulation. For neuroprotection, they are comparably priced to other neuroprotective botanicals like Bacopa monnieri or Ginkgo biloba, but with less clinical evidence supporting their use. For metabolic support, particularly for blood glucose management, there are more cost-effective options with stronger clinical evidence, such as berberine or cinnamon extracts.

Enhanced delivery systems such as nanoemulsions, liposomes, or SEDDS offer better bioavailability and potentially superior therapeutic outcomes, which may justify their higher cost for specific health conditions, particularly those affecting the central nervous system where blood-brain barrier penetration is important.

Pure hispidulin is moderately stable, with a typical shelf life of 2-3 years

when properly stored. The balanced hydroxyl/methoxy structure (three hydroxyl groups and one methoxy group) provides better stability compared to more hydroxylated flavonoids. Standardized herbal extracts containing hispidulin typically have a shelf life of 1-2 years from the date of manufacture. Enhanced delivery formulations such as nanoemulsions or liposomes generally have shorter shelf lives of 1-2 years, depending on the specific formulation and preservative system.

Store in a cool, dry place away from direct sunlight in airtight, opaque containers. Refrigeration is recommended for liquid formulations and can extend shelf life of extracts containing hispidulin. Protect from moisture, heat, oxygen, and light exposure, which can accelerate degradation. For research-grade pure hispidulin, storage under inert gas (nitrogen or argon) at -20°C is recommended for maximum stability.

For dried herb material (e.g., Artemisia or Salvia species), store in airtight containers away from light and moisture to preserve the hispidulin content. The addition of antioxidants such as vitamin E or ascorbic acid to formulations can help prevent oxidation and extend shelf life. Enhanced delivery formulations may have specific storage requirements provided by the manufacturer, which should be followed carefully to maintain stability and potency. Avoid repeated freeze-thaw cycles, particularly for liquid formulations, as this can destabilize the product.

Exposure to UV light and sunlight – causes photodegradation, though the methoxy group provides some protection compared to more hydroxylated flavonoids, High temperatures (above 30°C) – accelerates decomposition, Moisture – can promote hydrolysis and microbial growth, particularly in liquid formulations, Oxygen exposure – leads to oxidation, particularly of the hydroxyl groups, pH extremes – hispidulin is most stable at slightly acidic to neutral pH (5-7), Metal ions (particularly iron and copper) – can catalyze oxidation reactions, Enzymatic activity – may occur in improperly processed plant extracts, Incompatible excipients in formulations – certain preservatives or other ingredients may interact negatively with hispidulin, Repeated freeze-thaw cycles – can destabilize enhanced delivery formulations such as nanoemulsions or liposomes

Synthesis Methods

Natural Sources

Quality Considerations

Hispidulin itself was not identified or isolated until the modern era, but it is a constituent of several plants that have been used in traditional medicine systems for centuries. While the specific contribution of hispidulin to the traditional uses of these plants was unknown to ancient practitioners, it is now recognized as one of the bioactive compounds in these historically important medicinal materials. Hispidulin is primarily found in Artemisia species (sagebrush, wormwood), Salvia species (sage), and Clerodendrum petasites, all of which have rich histories in traditional medicine across various cultures. Artemisia species have been used in traditional medicine systems worldwide for thousands of years.

In Traditional Chinese Medicine (TCM), Artemisia annua (sweet wormwood or qinghao) has been used since at least 168 BCE, as documented in the ‘Fifty-two Prescriptions’ discovered in the Mawangdui Han Dynasty tombs. It was traditionally used to treat fevers, malaria, and hemorrhoids. The famous Chinese physician Ge Hong (283-343 CE) described the use of qinghao for treating malaria in his work ‘Handbook of Prescriptions for Emergencies.’ Artemisia vestita, another species containing hispidulin, has been used in Tibetan and Chinese medicine for treating inflammation, pain, and infectious diseases. In European herbal medicine, various Artemisia species, particularly Artemisia absinthium (wormwood), have been used since ancient times.

The Greek physician Dioscorides mentioned wormwood in his De Materia Medica in the 1st century CE for its digestive, antiparasitic, and fever-reducing properties. In medieval European herbalism, wormwood was one of the key ingredients in the famous ‘Four Thieves Vinegar,’ believed to protect against the plague. Salvia species, particularly Salvia officinalis (common sage), have an equally impressive history in traditional medicine. The genus name ‘Salvia’ derives from the Latin ‘salvare,’ meaning ‘to heal’ or ‘to save,’ reflecting its high regard in ancient medicine.

In ancient Egypt, sage was used to treat infertility, while ancient Greeks and Romans used it for a wide range of conditions, including ulcers, wounds, sore throats, and memory enhancement. The Roman physician Pliny the Elder described sage as a sacred herb and praised its medicinal properties in his Natural History. In medieval Europe, sage was one of the ingredients in ‘Four Thieves Vinegar’ and was considered a panacea, as reflected in the proverb: ‘Why should a man die who has sage in his garden?’ Clerodendrum petasites, another plant containing hispidulin, has been used in traditional Thai medicine for treating asthma, fever, cough, and inflammatory conditions. In Southeast Asian traditional medicine, it was also used for its antipyretic and analgesic properties.

Chamomile (Matricaria chamomilla), which contains small amounts of hispidulin, has been used medicinally for thousands of years in Egyptian, Greek, and Roman civilizations for its calming and anti-inflammatory properties. Hispidulin was first isolated and characterized in the mid-20th century as part of the scientific investigation into the active components of these traditional medicinal plants. Its structure was elucidated as 4′,5,7-trihydroxy-6-methoxyflavone, identifying it as a partially methoxylated flavone. Modern scientific interest in hispidulin began to grow in the late 20th and early 21st centuries as research revealed its interaction with GABAA receptors and its potential anxiolytic, anticonvulsant, and neuroprotective properties.

The discovery of hispidulin’s activity at GABAA receptors provided a scientific explanation for the traditional use of plants containing this compound for conditions that would now be recognized as anxiety, insomnia, and seizures. This represents a fascinating example of how modern pharmacological research can validate and explain traditional medicinal practices that evolved through centuries of empirical observation.

No meta-analyses specifically on hispidulin are currently available; most analyses focus on herbal extracts containing hispidulin or flavonoids as a group.

Limited ongoing trials specifically investigating hispidulin; most research remains at the preclinical stage, Several preclinical studies investigating hispidulin’s potential in neurodegenerative diseases, particularly focusing on its neuroprotective properties in Alzheimer’s and Parkinson’s disease models, Research on novel delivery systems to enhance hispidulin’s bioavailability and targeted delivery to the central nervous system, Investigations into hispidulin’s potential as an adjunctive therapy for epilepsy and anxiety disorders, Studies on the combination of hispidulin with conventional therapies for enhanced efficacy in various conditions, particularly cancer