Luteolin

Luteolin

1. Identity: Chemical, Botanical, and Physical Characterization

1.1 Chemical Identity

Luteolin is a subclass of flavones chemically known as 5,7,3′,4′-tetrahydroxyflavone. It is also systematically named under IUPAC nomenclature as 2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4H-chromen-4-one. With a molecular weight of 286.24 g/mol and a melting point of 330°C, luteolin is a flavonoid characterized by two benzene rings and hydroxyl groups, contributing to its diverse biological activities. Belonging to the flavone group of flavonoids, luteolin has a C6-C3-C6 structure and possesses two benzene rings (A, B), a third, oxygen-containing (C) ring, and a 2−3 carbon double bond. Luteolin also possesses hydroxyl groups at carbons 5, 7, 3′, and 4′ positions. Luteolin is a flavone, a type of flavonoid, with a yellow crystalline appearance.

1.2 Historical Isolation and Nomenclature

Luteolin is the main yellow dye from the Reseda luteola plant, used for dyeing since at least the first millennium B.C. This compound was first isolated in its pure form in 1829 by the French chemist Michel Eugène Chevreul. The luteolin empirical formula was determined by the Austrian chemists Heinrich Hlasiwetz and Leopold Pfaundler in 1864. In 1896, the English chemist Arthur George Perkin proposed the correct structure for luteolin.

1.3 Botanical Distribution and Natural Sources

This flavonoid and its glycosides are widely distributed in the plant kingdom; they are present in many plant families and have been identified in Bryophyta, Pteridophyta, Pinophyta, and Magnoliophyta. Luteolin is a phytochemical present in leaves, bark, flower blossoms, pollens, various vegetables, and herbs.

Particularly rich dietary and herbal sources include:

• Vegetables and fruits such as celery, parsley, broccoli, onion leaves, carrots, peppers, cabbages, apple skins, and chrysanthemum flowers are luteolin-rich.
• Additional dietary sources of luteolin include peppermint, thyme, rosemary, and oregano.
• Luteolin is found in medicinal plants like honeysuckle, Scutellaria (Lamiaceae), and dandelion (Asteraceae), as well as in crops like peanut shells and corn whiskers.

Luteolin is a naturally occurring secondary metabolite belonging to the class of flavones. As with many other natural flavonoids, it is often found in combination with glycosides in many fruits, vegetables, and plants, contributing to their biological and pharmacological value. Natural luteolin glycosides are present in plants in the form of luteolin C-glycosides or luteolin O-glycosides.

1.4 Common Supplement Forms and Preparations

Luteolin is commercially available as an isolated aglycone, as part of standardized plant extracts (e.g., from chamomile, Lonicera japonica, or artichoke), and in various enhanced-bioavailability formulations. Complexes of luteolin with cyclodextrin and phospholipids have shown promising results. Moreover, nanoencapsulation of luteolin in liposomes, micelles, and nanoparticles, as well as utilization of a microemulsion system, were able to improve in vivo luteolin's bioavailability and efficacy. One clinically tested form is a combination preparation: a dietary supplement containing luteolin (100 mg/capsule, from chamomile) and quercetin (70 mg/capsule), and the quercetin glycoside rutin (30 mg/capsule) from the Sophora japonica leaf, formulated in olive kernel oil to increase oral absorption. Another formulation studied is a co-ultramicronized combination of palmitoylethanolamide (PEA) with luteolin (co-ultra PEALut®), used in several neurological contexts.

2. Traditional and Historical Use

2.1 Traditional Chinese Medicine

Plants rich in luteolin have been used in Chinese traditional medicine for treating various diseases such as hypertension, inflammatory disorders, and cancer. Chinese traditional medicine makes extensive use of luteolin to treat numerous conditions, particularly inflammatory disorders, hypertension, and cancer. In the traditional Chinese medicine system, luteolin-enriched plants have been utilized to treat various ailments such as hypertension, inflammatory disorders, obesity, diabetes, and cancer. Key luteolin-bearing plants in this tradition include Lonicera japonica (Japanese honeysuckle) and Scutellaria baicalensis.

2.2 Use in Other Traditional Medical Systems

Plants with a high luteolin content have been used for a long time in Iranian, Brazilian, and Chinese traditional medicines to treat inflammation-related diseases. The use of luteolin as a liver-protecting agent has ancient origins, since this flavonoid is abundant in Achillea millefolium, a plant traditionally used to treat liver diseases in India. Flavonoids are also common constituents of plants used in traditional medicine to treat a wide range of diseases.

2.3 Historical Dyeing Use

The plant-level use of luteolin as a yellow textile dye predates its recognition as a medicinal compound. Luteolin is the main yellow dye from the Reseda luteola plant, used for dyeing since at least the first millennium B.C. This dyeing application reflects how widely luteolin-bearing plants were cultivated and harvested across ancient cultures, even when luteolin itself was not yet identified as the active constituent.

3. Key Chemical Constituents and Mechanisms of Action

3.1 Antioxidant Activity

Luteolin exerts a range of beneficial effects on human health, including antiallergic, anti-inflammatory, antidiabetic, neuroprotective, and anticancer effects. Due to their chemical nature, luteolin and its glycosides also display antioxidant properties, scavenging free radicals derived from oxidation and chelating metal ions. Research has shown that luteolin effectively removes free radicals generated in the body and enhances the cell's own antioxidant capacity, thereby reducing the impact of oxidative damage on cells.

3.2 Anti-Inflammatory Mechanisms

Anti-inflammatory activity is among the most extensively studied properties of luteolin. Luteolin suppresses NF-κB and MAPK signaling, activates the Nrf2/HO-1 pathway while inhibiting NOX4/NF-κB signaling, and downregulates TLR4/NF-κB signaling, NLRP3 inflammasome activation, and pyroptosis. In addition, it restores immune homeostasis by regulating macrophage polarization, balancing Th1/Th2 differentiation, and enhancing regulatory T cell (Treg) function.

At the molecular level, luteolin inhibits NF-κB activation by preventing phosphorylation of the p65 subunit, inhibits the translocation of p65 to the nucleus, inhibits NF-κB-induced production of cytokines, and inhibits production of reactive oxygen species (ROS), including superoxide. Luteolin has a strong antioxidant capacity to inhibit inflammation-associated gene expression (TNF-α, IL-6, iNOS, and COX-2) by suppressing redox-dependent NF-κB and AP-1 activation. In studies using mast cell lines, luteolin significantly inhibited the induction of inflammatory cytokines such as TNF-α, IL-8, IL-6, and GM-CSF, and also attenuated COX-2 expression and intracellular Ca²⁺ levels.

3.3 Anticancer Mechanisms

The ability of luteolin to inhibit angiogenesis, to induce apoptosis, to prevent carcinogenesis in animal models, to reduce tumor growth in vivo and to sensitize tumor cells to the cytotoxic effects of some anticancer drugs suggests that this flavonoid has cancer chemopreventive and chemotherapeutic potential. Modulation of ROS levels, inhibition of topoisomerases I and II, reduction of NF-κB and AP-1 activity, stabilization of p53, and inhibition of PI3K, STAT3, IGF1R and HER2 are possible mechanisms involved in the biological activities of luteolin.

Luteolin sensitizes cancer cells to therapeutic-induced cytotoxicity through suppressing cell survival pathways such as PI3K/Akt, NF-κB, and XIAP. It also stimulates apoptosis pathways induced by the tumor suppressor protein p53. Luteolin triggers apoptotic cell death through potentiation of both apoptosis pathways and suppression of cell survival pathways.

3.4 Neuroprotective Mechanisms

In vitro and in vivo experimentation shows that luteolin is able to inhibit microglial-associated inflammation pathways such as NF-κB and MAPK/AP-1, which produce pro-inflammatory cytokines associated with activating β-secretase and γ-secretase leading to stimulating amyloid-β (Aβ) formation. Luteolin prevents glutamate-induced neuronal apoptosis and reduces ROS accumulation. Remarkably, luteolin restores mitochondrial function, mitigates mitochondrial dysfunction, and curtails excessive autophagy and mitophagy.

3.5 Cardiovascular Mechanisms

Increasing evidence supports the mechanism by which luteolin prevents cardiovascular diseases by improving endothelial function and reducing low-density lipoprotein cholesterol (LDL-C) levels. Studies have shown that luteolin can enhance the synthesis and release of nitric oxide (NO) in endothelial cells, promoting vasodilation, thereby improving microcirculation and reducing the risk of cardiovascular diseases. In addition, luteolin can also inhibit the inflammatory response of endothelial cells, further protecting the integrity of the vascular endothelium.

3.6 Antidiabetic Mechanisms

Luteolin and its derivatives (O- and C-glycosides) possess several antidiabetic effects including improvement in blood glucose, insulin, HOMA-IR, and HbA1c levels, and decline in lipid synthesis. Luteolin helps fight diabetes via inhibition of alpha-glucosidase and cholinesterase activity. Antidiabetic effects of luteolin are also associated with increased expression of PPARγ and GLUT, which consequently improve glucose metabolism.

4. Scientific Evidence by Area of Use

4.1 Inflammation

Preclinical evidence (in vitro/in vivo, animal): The anti-inflammatory evidence base for luteolin is extensive but concentrated at the preclinical level. The protection mechanism of luteolin against LPS-induced acute lung injury was via the suppression of TNF-α and IL-6 productions, iNOS and COX-2 expressions, and NF-κB and Akt activation in mouse models. In alveolar macrophage cell lines, luteolin produced consistent inhibition of multiple inflammatory markers via NF-κB and AP-1 suppression.

Evidence quality: The anti-inflammatory mechanisms are well-characterized mechanistically across numerous in vitro systems and animal models. However, direct human interventional trials using isolated luteolin for inflammatory endpoints remain limited as of current literature. While preclinical studies in cellular and animal models are promising, and numerous studies indicate that luteolin has minimal toxicity, further research, particularly clinical trials in humans and rigorous toxicity experiments, are still required to assess its safety and promote its rational development.

4.2 Neuroprotection and Neurodegenerative Disease

Preclinical evidence (animal models): Numerous studies have shown that luteolin possesses beneficial neuroprotective effects both in vitro and in vivo. In rodent models of Alzheimer's disease, luteolin ameliorated Aβ-induced learning and memory impairment. In hippocampal tissue, the activity of choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) increased after treatment with luteolin. Luteolin also reversed the increased activity of acetylcholinesterase (AchE). The content of acetylcholine (Ach) increased, but malondialdehyde (MDA) reduced. For dosing in rodent cognitive models, oral doses reported in the literature range from 1.25 mg/kg to 200 mg/kg, with treatment length from 7 days to 5 months.

Human/clinical evidence: Although preclinical data show clear-cut neuroprotective effects of luteolin in AD models, there are no human intervention studies or clinical trials investigating its potential beneficial effects in AD patients. In January 2022, a double-blind, placebo-controlled, randomized clinical trial of the efficacy of luteolin (300 mg daily for 12 weeks) in patients with schizophrenia was registered at ClinicalTrials.gov (NCT05204407).

In the area of frontotemporal dementia, a randomized controlled trial on co-ultra PEALut in frontotemporal dementia has been completed. This study aimed to evaluate global disease severity and various executive functions including cognition changes (ClinicalTrials.gov Identifier: NCT04489017). However, the outcomes were not available as of May 2024.

Evidence quality: Neuroprotective evidence for luteolin remains preclinical. While animal model results are consistently positive, human clinical trial data are largely absent or pending publication. The evidence is therefore preliminary and cannot currently support clinical claims for any neurodegenerative indication.

4.3 Autism Spectrum Disorder (ASD)

Clinical evidence: This is one area in which limited clinical data exist. A dietary supplement containing luteolin (100 mg/capsule, from chamomile) and quercetin (70 mg/capsule), and the quercetin glycoside rutin (30 mg/capsule) from Sophora japonica, formulated in olive kernel oil, was tested in fifty children (4–10 years old; 42 boys and 8 girls) with ASD enrolled in a 26-week, prospective, open-label trial at the 2nd University Department of Psychiatry at "Attikon" General Hospital, Athens, Greece. The dose of the study formulation used was 1 capsule per 10 kg weight per day with food. Among the 50 children, 40 completed the protocol and showed significant improvement in adaptive functioning, as measured by the Vineland Adaptive Behavior Scales, and in overall behavior, as indicated by a reduction in Aberrant Behavior Checklist subscale scores.

Additionally, co-ultraPEA-LUT® treatment ameliorated social and nonsocial behaviors in valproic acid-induced autistic mice and improved the clinical picture with reduction in stereotypes in a 10-year-old male child.

Evidence quality: The ASD clinical evidence consists of a single small open-label trial (no placebo control, single-arm, 50 children) and a single pediatric case report. The luteolin formulations tested were multi-ingredient, making it impossible to isolate luteolin's independent effect. This evidence is preliminary and requires confirmation from randomized controlled trials.

4.4 Cancer

Preclinical evidence: Luteolin, a natural flavone present in significant amounts in various fruits and vegetables, plays a key role as a chemopreventive agent in treating various types of cancer. By inducing apoptosis, initiating cell cycle arrest, and decreasing angiogenesis, metastasis, and cell proliferation, luteolin is studied in cancer treatment. Its anticancer properties are attributed to its capability to engage with multiple molecular targeted sites and modify various signaling pathways in tumor cells. Luteolin has been shown to slow the spread of cancer in breast, colorectal, lung, prostate, liver, skin, pancreatic, oral, and gastric cancer models.

Human/clinical evidence: In a single-arm phase I study, oral intake of luteolin in patients under active surveillance for prostate cancer was clinically examined. Between March and September 2022, five patients with low–intermediate risk prostate cancer and under active surveillance were treated daily with 50 mg of oral luteolin for six months. In this phase I study of five patients, 180 days of 50 mg luteolin treatment was generally well-tolerated, and all five patients did not experience adverse events over time.

Evidence quality: Although there are currently no marketed products to support the clinical anticancer effects of luteolin, a search of the ClinicalTrials.gov website reveals that clinical trials of luteolin are already registered. At present, the studies on the anticancer effect of luteolin are stuck in the cell and animal stages, lacking a high clinical basis. The prostate cancer phase I study is notable but extremely small (n=5) and was primarily a safety assessment, not a definitive efficacy trial. Overall, anticancer evidence for luteolin in humans remains preliminary.

4.5 Cardiovascular Disease

Preclinical evidence: A systematic review and meta-analysis of preclinical evidence specifically examined luteolin in myocardial ischemia-reperfusion injury (MIRI). Luteolin administration was confirmed to reduce infarct size (IS) and ameliorate hemodynamics as compared to the control groups (p < 0.01). IS had decreased by 2.50%, 2.14%, 2.54% in three subgroups. Amelioration of hemodynamics was apparent in two different myocardial infarct models, as left ventricular systolic pressure improved, left ventricular end-diastolic pressure decreased, and maximum rates of left ventricular pressure rise and decrease improved significantly. Pooling of the data demonstrated that luteolin exerts cardioprotective effects against MIRI through different signaling pathways. As possible mechanisms, luteolin exerts anti-apoptosis, anti-oxidation, and anti-inflammation effects against MIRI.

Luteolin plays a positive role against cardiovascular disorders by improving cardiac function, decreasing the release of inflammatory cytokines and cardiac enzymes, and prevention of cardiac fibrosis and hypertrophy.

Evidence quality: Research on luteolin in the cardiovascular domain has been limited to preclinical trials, as most findings have been obtained from animal studies. Human interventional trials for cardiovascular endpoints using luteolin have not yet been published. Evidence is promising but not translatable without confirmed clinical data.

4.6 Diabetes and Metabolic Disorders

Preclinical evidence: Luteolin binds to Forkhead box protein O1 and glutamine-fructose-6-phosphate aminotransferase, which highlights that it has a potential role in avoiding hyperglycemia, hence luteolin proved to be a potential molecule in controlling Type 2 diabetes. Luteolin ameliorated diabetes by enhancing insulin secretion, improving β-cell dysfunction, insulin resistance, and endothelial function, and reducing inflammation via modulation of NF-κB, IL-6, TNF-α, and PPARγ expression in preclinical models.

Evidence quality: The antidiabetic evidence base is entirely preclinical (cell culture and animal models) as of available literature. No registered human trials evaluating luteolin specifically for diabetes management as a primary endpoint have been identified in published literature. This area must be considered exploratory.

4.7 Respiratory Diseases (Asthma, COPD, Pulmonary Inflammation)

Preclinical/limited clinical evidence: A clinical study confirms that luteolin (2 μmol/L) reduces IL-6 and TNF-α via TLR4/NF-κB signaling, supporting its potential in managing pediatric allergic asthma. The broader evidence for respiratory conditions relies heavily on in vitro and animal model data, demonstrating consistent effects on airway inflammation markers, oxidative stress, and immune cell regulation.

Evidence quality: Luteolin exhibits favorable safety and distribution profiles in lung tissue in preclinical studies, highlighting its potential as a therapeutic candidate for inflammatory respiratory diseases. Nevertheless, further preclinical and clinical investigations are required to validate its efficacy, safety, and translational applicability in clinical practice.

4.8 Pain and Neuropathic Conditions

Preclinical evidence and some limited clinical observation support luteolin's potential in pain management, primarily through its established anti-inflammatory and neuroinflammation-inhibiting mechanisms. There is a recognized need for clinical studies proving these effects in humans. No adequately powered randomized human trials specifically measuring analgesic efficacy of isolated luteolin have been identified in the published literature.

5. Body Systems and Health Areas Associated with Luteolin

Based on the peer-reviewed literature, the following body systems and health areas are subject to active research on luteolin:

• Central Nervous System: Neuroprotection, neuroinflammation inhibition, Alzheimer's disease models, Parkinson's disease, frontotemporal dementia, autism spectrum disorder, anti-anxiety and antidepressant-like effects in preclinical models.
• Cardiovascular System: Myocardial ischemia-reperfusion injury protection, cardiac hypertrophy, endothelial function, vascular inflammation, anti-atherosclerotic potential.
• Metabolic / Endocrine System: Blood glucose regulation, insulin sensitivity, inhibition of alpha-glucosidase, lipid metabolism.
• Immune System: Mast cell stabilization, macrophage polarization regulation, Th1/Th2 balance, anti-allergic effects.
• Respiratory System: Asthma, acute lung injury, COPD, pulmonary fibrosis models.
• Oncology: Chemopreventive and potential chemotherapeutic activity across multiple cancer types (breast, prostate, colorectal, lung, liver, pancreatic, skin, oral, gastric).
• Hepatic System: Hepatoprotection, acute liver injury attenuation.
• Renal System: Renoprotective effects demonstrated in preclinical models.

Luteolin has demonstrated a variety of pharmacological influences in both in vitro and in vivo studies, possessing characteristics of antioxidant, anti-tumor, anti-microbial, anti-viral, anti-inflammatory, anti-apoptotic, anti-allergic, anti-diabetic, chemopreventive, renoprotective, cardioprotective, and neuroprotective properties. Additionally, luteolin has shown anti-anxiety, antidepressant-like, antipruritic, hepatoprotective, and antithrombotic activity.

6. Dosage Forms and Reported Dosages

Dosages reported in the peer-reviewed literature span a wide range depending on the study type, population, and clinical target. The following are drawn directly from published studies:

• Prostate cancer active surveillance (Phase I human trial): 50 mg of oral luteolin daily for six months was the dose tested in five patients with low–intermediate risk prostate cancer.
• ASD in children (open-label clinical trial): A supplement providing luteolin 100 mg/capsule (from chamomile), quercetin 70 mg/capsule, and rutin 30 mg/capsule, formulated in olive kernel oil, was administered at 1 capsule per 10 kg body weight per day with food over 26 weeks.
• Schizophrenia (registered RCT): 300 mg daily for 12 weeks was the registered dose in a double-blind, placebo-controlled trial (NCT05204407).
• Animal models of cognitive dysfunction (rodent oral doses): Oral doses range from 1.25 mg/kg to 200 mg/kg, with treatment length from 7 days to 5 months.
• Animal model of ASD: Luteolin 100 mg/kg/d combined with exercise was used in Aβ1-42 oligomer mouse models of Alzheimer's disease.
• Asthma (animal model in vivo): Luteolin 2 mg/kg intraperitoneal injection was used in OVA-induced juvenile rat models.

No established human therapeutic dose has been validated through phase III randomized controlled trials for any indication as of the available literature.

7. Bioavailability and Pharmacokinetics

Luteolin, a naturally occurring polyphenol, is poorly water-soluble. The low bioavailability of luteolin, reported at 4.10% at a dose of 50 mg/kg in rats, is presumably due to a significant first-pass effect. For intravenous administration, the plasma concentration versus time profile of luteolin was biphasic, subdivided into a distribution phase and a slow elimination phase. Luteolin was found to have a large volume of distribution and a high clearance.

Due to the low bioavailability and poor solubility of luteolin, systemic administration of luteolin may not result in the desired therapeutic effect in clinical trials. Strategies to enhance water solubility and bioavailability through chemical modifications and advanced pharmaceutical formulations such as nanovesicles and cyclodextrin complexes hold promise for addressing these challenges. The solubility and bioactivity of luteolin can also be improved by glycosylation.

8. Safety Considerations and Drug Interactions

8.1 General Safety Profile

While preclinical studies in cellular and animal models are promising, and numerous studies indicate that luteolin has minimal toxicity, further research, particularly clinical trials in humans and rigorous toxicity experiments, are still required to assess its safety fully. The available human safety data are limited to small pilot studies. In the prostate cancer phase I study, 180 days of 50 mg luteolin treatment was generally well-tolerated, and all five patients did not experience adverse events over time.

8.2 Drug–Drug Interactions: CYP450 and Transport Proteins

Luteolin and naringenin are flavonoids found in various foods/beverages and present in certain dietary supplements. After a high intake of these flavonoids, their sulfate and glucuronide conjugates reach micromolar concentrations in the bloodstream. Regarding CYP enzyme effects, luteolin and naringenin conjugates showed no or only weak inhibitory action on the CYP enzymes examined. However, certain conjugates of luteolin and naringenin are potent inhibitors of OATP1B1 and/or OATP2B1 enzymes. These organic anion transporting polypeptides (OATPs) are involved in the hepatic uptake of many drugs.

A notable interaction has been identified with statins. Luteolin nanosuspensions could significantly increase systemic exposure to atorvastatin by inhibiting CYP450 and OATP activities. The combined application strategy was suggested to run atorvastatin at half of the highest dosage recommended by guidelines. This finding, while derived from rat models extrapolated to humans via physiologically based pharmacokinetic (PBPK) modeling, indicates a potential clinically relevant interaction requiring further investigation before concurrent use of luteolin supplements with statins can be considered routine.

8.3 Potential Genotoxicity Under Certain Enzymatic Conditions

A specific safety signal has been identified in vitro: the flavonoids diosmetin and luteolin exert synergistic cytostatic effects in human hepatoma HepG2 cells via CYP1A-catalyzed metabolism, activation of JNK and ERK, and P53/P21 up-regulation. Research in human lymphoblastoid TK6 cells has indicated that the genotoxic potential of luteolin may be enhanced by CYP1A1 and CYP1A2, suggesting that individuals with particular CYP1A expression profiles could have differential responses. This has been observed only in vitro and its clinical relevance in humans has not been established.

8.4 Estrogenic Activity Considerations

Luteolin has been reported to interact with estrogen biosynthesis pathways. At the molecular level, luteolin can modulate aromatase (CYP19) enzyme activity and estrogen receptor signaling in cell culture models. Luteolin synergistically downregulates two major therapeutic targets, ERα and the CDK4/6/retinoblastoma pathway, in both cultured cells and xenograft tumors in the context of combination anti-breast cancer research. The implications of this for women taking hormone therapies have not been adequately studied in humans.

8.5 Bioavailability Enhancement and Pro-Oxidant Potential

Having multiple biological effects such as anti-inflammation, anti-allergy, and anticancer, luteolin functions as either an antioxidant or a pro-oxidant biochemically. This dual nature is concentration-dependent, with pro-oxidant activity observed at higher concentrations in certain cell culture systems. The concentration ranges at which pro-oxidant effects occur in humans following dietary or supplemental intake are not established.

8.6 Pregnancy and Special Populations

The safety of isolated luteolin supplementation during pregnancy has not been evaluated in human studies. The available literature references flavonoid safety reviews noting uncertainty regarding developmental effects of flavonoid-based supplements in pregnancy.

9. Summary of Evidence Strength

The following characterizes the overall state of evidence for luteolin by domain:

• Anti-inflammatory mechanisms: Well-established in vitro and in animal models; clinical human evidence is very limited and largely indirect.
• Antioxidant activity: Well-characterized mechanistically; clinical significance in humans is unconfirmed.
• Neuroprotection / Alzheimer's disease: Consistent positive findings in rodent models; no completed human clinical trial data currently published.
• Autism spectrum disorder: One small open-label pilot trial (n=50, no control arm, multi-ingredient formulation) and one case report; evidence is preliminary only.
• Cancer prevention/treatment: Extensive preclinical evidence across multiple cancer types; one very small Phase I safety trial (n=5); no phase II/III efficacy data in humans.
• Cardiovascular protection: Systematic review of positive preclinical findings; no human clinical trials published.
• Diabetes / metabolic syndrome: Preclinical evidence only.
• Respiratory disease: Primarily preclinical; one report of cytokine reduction in a clinical context.

Many preclinical studies report that luteolin presents excellent antioxidant, anticancer, antimicrobial, neuroprotective, cardioprotective, antiviral, and anti-inflammatory effects, and as a consequence, various clinical trials have been designed to investigate the therapeutic potential of luteolin in humans. The overall body of clinical evidence remains nascent, and for most indications, translation from preclinical to human settings has not yet been achieved.

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