Apigenin Encyclopedia — Scientific Background

What Is Apigenin?

Apigenin (CAS 520-36-5), also known as 4′,5,7-trihydroxyflavone or 5,7-dihydroxy-2-(4-hydroxyphenyl)-4H-chromen-4-one, is a naturally occurring flavone belonging to the flavonoid class of plant secondary metabolites. It is chemically characterized by the molecular formula C₁₅H₁₀O₅ and a molecular weight of 270.24 g/mol. Apigenin is a yellow crystalline powder that is practically insoluble in water. It is widely distributed in the plant kingdom, with the richest dietary sources being parsley, chamomile, and celery.

Botanical Sources

Apigenin is widely found in vegetables, fruits, and herbs. The most important dietary sources include:

• Parsley — 45,035 μg/g, the richest known dietary source

• Chamomile — 3,000–5,000 μg/g in dried flower heads; chamomile infusion contains 0.8–1.2% apigenin

• Celery Seeds — 786.5 μg/g

• Vine Spinach — 622 μg/g

• Chinese Celery — 240.2 μg/g

Apigenin was first identified in the form of its glucoside (apiin) in parsley extracts. The commercial extract is primarily derived from chamomile flower heads through processes including solvent extraction, purification, and crystallization.

Mechanisms of Action

Senomorphic Activity — SASP Modulation

Apigenin exhibits senomorphic potential, modulating the senescence-associated secretory phenotype (SASP) without necessarily eliminating senescent cells. This activity is distinct from senolytic agents such as fisetin and quercetin, which selectively eliminate senescent cells. Apigenin's senomorphic effects contribute to its anti-aging and cellular health benefits by reducing the pro-inflammatory secretions of senescent cells.

Neuroprotective Effects — Antioxidant and Anti-Amyloid Pathways

Apigenin is a strong antioxidant that effectively delays peripheral neurodegenerative processes. Research indicates that apigenin exerts neuroprotective effects through multiple mechanisms, including modulation of key cellular pathways such as mTOR, Wnt/β-catenin, NF-κB, and TRAIL-induced apoptosis. It has demonstrated the ability to protect against oxidative stress and neurodegeneration in preclinical models of Alzheimer's disease, Parkinson's disease, and other neurodegenerative conditions.

Anxiolytic and Sleep-Promoting Activity — GABA-A Receptor Modulation

Apigenin acts as a GABA-A receptor modulator and has been identified as a bioactive compound in chamomile tea responsible for its calming effects. While human clinical evidence remains limited, a randomized, double-blind, placebo-controlled study of chamomile extract in patients with anxiety and depression demonstrated partial anxiolytic benefit. Only four human clinical trials have specifically examined apigenin's effects on sleep quality, with mixed results.

Anti-Inflammatory Activity — COX and CYP Inhibition

Apigenin inhibits pro-inflammatory mediators such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and nuclear factor kappa B (NF-κB). It also acts as a competitive CYP2C9 inhibitor (Ki = 2 μM), which may contribute to its pharmacological effects through modulation of drug-metabolizing enzymes.

Antioxidant Defense

Apigenin scavenges free radicals and reactive oxygen species, protecting cells from oxidative damage. Its antioxidant capacity is enhanced in liposomal formulations, with chitosan-coated apigenin liposomes demonstrating higher antioxidant capacity than free apigenin.

The Bioavailability Challenge

Despite its broad pharmacological potential, apigenin presents significant formulation challenges. The compound has poor aqueous solubility (less than 1 μg/mL to 2.16 μg/mL), chemical instability, and low bioavailability, severely limiting its potential utilization in functional foods. Apigenin may also be inactivated in the gastrointestinal acidic environment, resulting in low bioavailability in vivo.

These limitations have driven the development of advanced delivery systems, including liposomes, nanoemulsions, microcapsules, and polymeric nanoparticles. Among these, liposomal encapsulation has emerged as one of the most effective strategies for enhancing apigenin bioavailability and therapeutic efficacy. The significant stability of the obtained amorphous apigenin dispersion was demonstrated for 12 months, and chitosan-coated apigenin liposomes demonstrated improved aqueous solubility and stability against simulated gastrointestinal digestion.

Liposomal apigenin

Liposomal encapsulation of apigenin provides a fundamentally different delivery mechanism from conventional forms. The phospholipid bilayer surrounds the apigenin molecule, forming a protective shell that enhances solubility, stability, and cellular uptake. This delivery system:

• Dramatically enhances apigenin solubility and dispersibility in aqueous systems

• Protects apigenin from oxidative and gastrointestinal degradation

• Improves intestinal absorption through lipid-mediated pathways

• Provides sustained release for prolonged cellular support

• Achieves up to 262% increase in relative bioavailability compared to free apigenin

A dual-drug loaded liposomal nanocarrier bearing the anti-tumorigenic agent apigenin was designed to improve the bioavailability of the flavone while achieving a combinatorial drug regimen with 5-fluorouracil. The dual drug loaded liposomal nanocarrier provided scope for improved bioavailability by circumventing the impediment posed by the high hydrophobicity of the flavone. Apigenin-loaded stealth liposomes demonstrated better plasma retention time and stability compared to standard apigenin, with improved bioavailability and enhanced antitumor efficacy.

Clinical Evidence

Human Clinical Trials — Current Status

A PubMed analysis spanning 2000–2024 identified 23 human trials investigating any apigenin-related endpoint. Of these, only four human clinical trials have specifically examined apigenin's effects on sleep quality, with mixed results. Most human studies have used chamomile extract standardized to apigenin rather than isolated apigenin.

Anxiety and Depression

A randomized, double-blind, placebo-controlled study evaluated chamomile extract in participants with both anxiety and depression. The intervention used 200–1,000 mg of chamomile extract per day for 8 weeks, standardized to 1.2% apigenin. Only one human study has shown partial anxiolytic benefit, with participants reporting improvements in anxiety and depression symptoms.

Sepsis — Ongoing Clinical Trial

A randomized clinical trial (NCT05999682) is evaluating apigenin for improving organ function in elderly patients with sepsis. The treatment group receives apigenin tablets (50 mg, ground with 5 mL of sterilized water for intragastric tube injection) plus conventional standardized treatment, for 4 days or until ICU discharge.

Preclinical Evidence — Cancer, Cardiovascular, and Diabetes

Preclinical research highlights apigenin's effectiveness across numerous biological processes, including anti-inflammatory, antioxidant, anti-cancer, anti-diabetic, and neuroprotective activities. Emerging clinical studies are beginning to affirm apigenin's therapeutic benefits, showing positive effects in treating cancer, cardiovascular diseases, diabetes, neurodegenerative disorders, and inflammatory conditions.

Safety and Regulatory

Apigenin is generally well tolerated at commonly consumed doses. Apigenin exerts no cases of toxicity even when administered in high dosage in preclinical studies. In a clinical trial, administering apigenin at a higher dose (32 μg/mL) confirmed that the effect on the hemolysis of erythrocytes and the cytotoxicity of Vero cells was negligible.

However, human evidence remains limited. Only 23 human trials investigating any apigenin endpoint have been published, and no human clinical trial has yet measured whether apigenin supplements produce meaningful therapeutic effects in people at the doses commonly consumed. The toxicological profile of apigenin includes safety concerns such as potential genotoxicity at higher concentrations.

Apigenin is widely commercialized as a dietary supplement ingredient. It is available in the United States, Europe, and other regions. Regulatory status varies by region, and formulators should verify local requirements prior to market entry. Testing protocols must adhere to international standards including USP, European Pharmacopoeia, and FAO/WHO Codex Alimentarius.

This product is intended for research, nutraceutical, and functional food applications. Not intended to diagnose, treat, cure, or prevent any disease.

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