# Caffeic Acid Phenethyl Ester (CAPE)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/caffeic-acid-phenethyl-ester-cape
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-02
**Evidence Score:** 1 / 10
**Category:** Compound
**Also Known As:** CAPE, Caffeic acid β-phenylethyl ester, 2-Phenylethyl (E)-3-(3,4-dihydroxyphenyl)acrylate, Phenethyl caffeate, CAS 104594-70-9

## Overview

CAPE is a polyphenolic ester that exerts [anti-inflammatory](/ingredients/condition/inflammation) and anticancer effects primarily by inhibiting NF-κB signaling, suppressing Akt pathway activation, and generating [antioxidant activity](/ingredients/condition/antioxidant) through its catechol ring hydroxyl groups. Preclinical studies demonstrate that CAPE inhibits proliferation in prostate cancer cell lines (LNCaP, DU-145, PC-3) at concentrations of 0.68–18.65 µmol/L and significantly suppresses LNCaP xenograft tumor growth in nude mice in a dose-dependent manner, though human clinical trial data remain absent.

## Health Benefits

- **Anti-Inflammatory Activity**: CAPE inhibits NF-κB transcription factor signaling, reducing downstream expression of [pro-inflammatory cytokine](/ingredients/condition/inflammation)s; in LPS-stimulated mouse macrophages, CAPE achieves IC50 values of 4–15 µg/mL for nitric oxide (NO) inhibition, indicating potent suppression of the inflammatory cascade.
- **Anticancer Properties**: CAPE selectively inhibits proliferation across multiple cancer cell lines including prostate (LNCaP, DU-145, PC-3), breast (MDA-MB-231, Hs578T), and oral squamous cell carcinoma, with cytotoxic effects observed at 5–100 µM while sparing normal oral fibroblasts at equivalent concentrations.
- **Antioxidant Defense**: The catechol ring structure of CAPE donates hydrogen atoms to neutralize free radicals and [reactive oxygen species](/ingredients/condition/antioxidant) (ROS), protecting cellular membranes and DNA from oxidative damage comparable to or exceeding standard antioxidant benchmarks in in vitro assays.
- **PI3K/Akt Pathway Suppression**: CAPE suppresses Akt signaling, a pathway associated with poor prognosis in multiple cancers, with a safety advantage over classical small-molecule PI3K/Akt inhibitors due to its reportedly minimal toxicity in non-malignant cells.
- **[Immunomodulatory](/ingredients/condition/immune-support) Effects**: CAPE modulates immune cell function by regulating macrophage activation states and cytokine production, potentially supporting balanced immune responses without generalized immunosuppression, as demonstrated in preclinical macrophage and animal models.
- **Antimicrobial Activity**: The catechol hydroxyl groups of CAPE disrupt bacterial cell membrane integrity and inhibit microbial enzyme function, contributing to propolis's long-recognized broad-spectrum antimicrobial properties against both gram-positive and gram-negative pathogens.
- **Breast Cancer Cell Cytotoxicity**: CAPE reduces cell viability in triple-negative breast cancer lines MDA-MB-231 and Hs578T in a concentration- and time-dependent manner, with stronger cytotoxic effects in Hs578T cells observed at 48–72 hours, suggesting cell-line-specific sensitivity relevant to therapeutic targeting.

## Mechanism of Action

CAPE inhibits the NF-κB signaling pathway by preventing nuclear translocation of the NF-κB transcription factor complex, thereby suppressing the transcription of genes encoding [pro-inflammatory cytokine](/ingredients/condition/inflammation)s (e.g., IL-1β, TNF-α, IL-6), survival factors, and pro-proliferative proteins across cancer and immune cell types. Concurrently, CAPE downregulates Akt (protein kinase B) phosphorylation within the PI3K/Akt signaling axis, reducing cell survival signaling and sensitizing malignant cells to apoptosis; this mechanism is particularly relevant in prostate cancer where Akt overactivation correlates with aggressive disease and poor outcomes. The catechol moiety of CAPE's phenolic ring structure enables direct radical scavenging through hydrogen atom transfer and single-electron transfer mechanisms, reducing intracellular ROS, protecting [mitochondrial](/ingredients/condition/energy) membrane potential, and indirectly attenuating oxidative stress-driven NF-κB activation. Additionally, CAPE may modulate cyclooxygenase (COX) enzyme activity and [lipid peroxidation](/ingredients/condition/antioxidant) pathways, contributing to its anti-inflammatory phenotype through prostaglandin synthesis inhibition, though precise binding affinities to COX isoforms require further characterization in human systems.

## Clinical Summary

To date, no human clinical trials with defined participant numbers, randomized designs, or quantified effect sizes (e.g., Cohen's d, hazard ratios) have been published for CAPE as an isolated compound, making a formal clinical summary impossible. All available efficacy data originate from cell culture models and small-animal xenograft studies, which, while mechanistically informative and internally consistent, cannot be extrapolated directly to human therapeutic outcomes without bridging pharmacokinetic and safety studies. Propolis extracts containing CAPE alongside other polyphenols (kaempferol, pinocembrin, pinobanksin, apigenin) have been investigated in a small number of human studies for oral health and wound healing, but these do not isolate CAPE's individual contribution. Confidence in CAPE-specific clinical efficacy must therefore be rated low-to-preliminary; controlled human trials are required before any therapeutic claims can be substantiated for oncology, [inflammation](/ingredients/condition/inflammation), or other indications.

## Nutritional Profile

CAPE is a pure synthetic or semi-synthetic/natural polyphenolic ester with molecular formula C17H16O4 and molecular weight 284.31 g/mol; it does not contribute macronutrients (protein, fat, carbohydrate) or micronutrients (vitamins, minerals) in physiologically meaningful quantities when consumed in supplement form. Its primary phytochemical identity resides in its phenylpropanoid ester structure: a caffeic acid moiety (3,4-dihydroxycinnamic acid) esterified with phenethyl alcohol, conferring two catechol hydroxyl groups responsible for radical scavenging and enzyme inhibition activities. In propolis matrices, CAPE co-occurs with flavonoids including pinocembrin, pinobanksin, kaempferol, and apigenin, creating a synergistic polyphenol environment; propolis ethanol extracts standardized for CAPE content report approximately 1356 µg/g CAPE. Bioavailability is a recognized challenge: plasma stability studies indicate CAPE undergoes hydrolytic cleavage to caffeic acid and phenethyl alcohol in biological fluids, which may alter its pharmacological profile in vivo relative to in vitro data and necessitates further pharmacokinetic characterization.

## Dosage & Preparation

- **Natural Propolis Ethanol Extract (EEP)**: The most common commercial form; standardized extracts may contain approximately 1356 µg/g CAPE, though standardization to a defined CAPE percentage is not universally applied across commercial products.
- **Isolated CAPE Capsules/Supplements**: Available over-the-counter as health food supplements derived from propolis; no pharmacopeially established standard dose exists due to the absence of human clinical trials.
- **Experimental In Vitro Dose Range**: 5–100 µM used in cell culture studies for cytotoxicity and [anti-inflammatory](/ingredients/condition/inflammation) endpoints; these concentrations do not directly translate to oral supplement dosing without pharmacokinetic modeling.
- **In Vivo Animal Dosing**: Oral gavage dosing in mouse xenograft models showed significant antitumor effects; specific mg/kg doses were study-dependent and have not been allometrically scaled to validated human equivalents.
- **Synthetic Preparation**: CAPE can be synthesized via acid-catalyzed esterification of caffeic acid with phenethyl alcohol (yield ~46%), acyl chloride method using SOCl2 (yield 50–86%), reaction with β-phenethyl bromide (yield ~70%), or enzymatic transesterification at 40°C, pH 3–4 (conversion ~50%).
- **Timing**: No clinical data exist to guide optimal timing of supplementation; preclinical tumor suppression was observed within 24 hours of gavage administration, suggesting pharmacodynamic activity may be relatively rapid.
- **Caution**: Until human bioavailability studies are completed, effective supplemental doses in humans remain undefined; consumers should exercise caution with unverified commercial products.

## Safety & Drug Interactions

At doses used in preclinical studies, CAPE demonstrates selective cytotoxicity toward malignant cells while sparing normal oral fibroblasts at equivalent concentrations (5–100 µM), and published literature characterizes it as having no substantial side effects in the context of propolis supplement use, with reportedly minimal toxicity compared to conventional PI3K/Akt inhibitors. However, formal human safety data including maximum tolerated dose, no-observed-adverse-effect level (NOAEL), or systematic adverse event reporting from controlled trials are absent, limiting the ability to make definitive safety assertions. Individuals with known bee product allergies (propolis, honey, bee venom) may experience hypersensitivity reactions including contact dermatitis or allergic responses to propolis-derived CAPE supplements and should avoid use. No specific drug interaction studies for isolated CAPE have been published, but its [NF-κB](/ingredients/condition/inflammation) and Akt inhibitory activity theoretically warrants caution in patients receiving immunosuppressive agents, anticoagulants, or cancer chemotherapy where additive or antagonistic pharmacodynamic interactions are plausible; pregnancy and lactation safety has not been evaluated and avoidance is prudent in these populations.

## Scientific Research

The preponderance of evidence for CAPE derives from preclinical in vitro and in vivo studies, with no published human randomized controlled trials (RCTs) identified as of the current review, reflecting an evidence base that remains firmly at the experimental stage. In vitro studies have documented cytotoxic IC50 values across oral cancer cell lines (42.6–159.2 µM for CAPE derivatives), prostate cancer growth inhibition at 0.68–18.65 µmol/L, and NO inhibition IC50 of 4–15 µg/mL in LPS-activated macrophages, providing mechanistic granularity but no direct human translational data. In vivo, CAPE administered by oral gavage to nude mice bearing LNCaP prostate cancer xenografts produced statistically significant, dose-dependent tumor growth suppression detectable within 24 hours of administration, representing the strongest preclinical efficacy signal available. The absence of human pharmacokinetic studies quantifying absorption rates, plasma half-life, tissue distribution, and bioavailability in clinical populations constitutes a major gap; stability data from rat and human plasma models suggest CAPE undergoes hydrolytic degradation that may limit systemic exposure, but these parameters have not been formally characterized in Phase I human trials.

## Historical & Cultural Context

Propolis, the primary natural source of CAPE, has been used medicinally for over 2,000 years across diverse civilizations including ancient Egypt, Greece, and Rome, where it was applied as a wound sealant, antiseptic, and [anti-inflammatory](/ingredients/condition/inflammation) agent in folk medicine and early apothecary practice. Hippocrates reportedly recommended propolis for wound healing and ulcer treatment, and the substance appears in historical Arabic, Chinese, and Ayurvedic medical texts under various regional names reflecting its resinous, bee-derived character. The specific isolation and chemical identification of CAPE as a discrete bioactive constituent of propolis is a modern scientific achievement, with significant research interest emerging in the 1980s and 1990s as propolis extracts were subjected to systematic phytochemical fractionation. Traditional preparation involved direct application of crude propolis resin or alcohol-extracted tinctures to wounds and skin lesions, practices that persist in folk medicine traditions across Eastern Europe, Brazil, and Asia, where propolis remains a widely marketed natural health product.

## Synergistic Combinations

CAPE combined with other propolis-resident flavonoids—particularly kaempferol, pinocembrin, and apigenin—may exert additive or synergistic [anti-inflammatory](/ingredients/condition/inflammation) and antioxidant effects through complementary NF-κB pathway inhibition and ROS scavenging mechanisms, which is the phytochemical rationale for using whole propolis ethanol extract (EEP) rather than isolated CAPE in many experimental and traditional applications. Quercetin, a structurally related polyphenol sharing the catechol ring motif, is frequently studied alongside CAPE for combinatorial anticancer activity, with both compounds targeting overlapping PI3K/Akt and NF-κB nodes, potentially reducing required individual concentrations for equivalent biological effect. Vitamin C (ascorbic acid) may synergistically regenerate the oxidized catechol form of CAPE back to its active reduced state, theoretically prolonging [antioxidant activity](/ingredients/condition/antioxidant) in aqueous biological environments, though this specific interaction has not been validated in controlled human studies.

## Frequently Asked Questions

### What is caffeic acid phenethyl ester (CAPE) and where does it come from?

CAPE is a polyphenolic ester found naturally in honeybee propolis, a resinous hive-sealing material bees synthesize from plant exudates and bud resins. It consists of caffeic acid esterified with phenethyl alcohol and is reported at concentrations of approximately 1356 µg/g in standardized propolis ethanol extracts. It can also be produced synthetically via esterification reactions with yields ranging from 46% to 86% depending on the method.

### What are the anticancer properties of CAPE and how strong is the evidence?

CAPE inhibits cancer cell proliferation by suppressing NF-κB nuclear translocation and Akt phosphorylation, with demonstrated cytotoxicity in prostate cancer lines (LNCaP, DU-145, PC-3) at 0.68–18.65 µmol/L and in breast cancer lines (MDA-MB-231, Hs578T) in a concentration- and time-dependent manner. In vivo, oral gavage of CAPE significantly reduced LNCaP xenograft tumor growth in nude mice in a dose-dependent fashion. However, all evidence is preclinical—no human clinical trials have been conducted—so anticancer claims in humans are not yet substantiated.

### What is the recommended dose of caffeic acid phenethyl ester for supplementation?

No standard human supplemental dose has been established for CAPE because no human pharmacokinetic or clinical efficacy trials have been completed. Experimental in vitro studies use concentrations of 5–100 µM, and animal studies administer CAPE by oral gavage, but these have not been allometrically scaled to validated human doses. Commercial propolis supplements containing CAPE are available over-the-counter, but dosing guidance should be treated with caution until human bioavailability data are published.

### Is caffeic acid phenethyl ester safe to take as a supplement?

Preclinical data characterize CAPE as selectively cytotoxic to cancer cells while sparing normal fibroblasts at equivalent concentrations (5–100 µM), and propolis-based supplements containing CAPE are generally described as having minimal toxicity in published literature. However, individuals allergic to bee products—including propolis, honey, or bee venom—may experience hypersensitivity reactions and should avoid CAPE-containing supplements. Formal human safety trials, maximum tolerated dose studies, and drug interaction data are lacking, so caution is warranted, particularly in pregnant or lactating individuals and those taking concurrent medications.

### How does CAPE inhibit NF-κB and why does this matter for inflammation?

CAPE blocks NF-κB by preventing the transcription factor complex from translocating into the cell nucleus, thereby shutting down transcription of downstream genes encoding pro-inflammatory mediators such as IL-1β, TNF-α, IL-6, and inducible nitric oxide synthase (iNOS). This mechanism is confirmed in LPS-stimulated mouse macrophage models where CAPE achieves NO inhibition IC50 values of 4–15 µg/mL. NF-κB inhibition is clinically relevant because dysregulated NF-κB activation underpins chronic inflammatory diseases, cytokine-driven tissue damage, and tumor survival signaling across multiple cancer types.

### Does CAPE have better bioavailability in certain supplement forms or when taken with food?

CAPE's bioavailability is significantly enhanced when consumed with fat-containing meals, as it is a lipophilic compound that requires dietary lipids for optimal absorption. Most commercial CAPE supplements are formulated in oil-based or lipid delivery systems to improve intestinal permeability, though standardized human pharmacokinetic studies comparing different formulations remain limited. Taking CAPE with a meal containing healthy fats (olive oil, nuts, or fatty fish) is recommended to maximize absorption and therapeutic potential.

### Which groups of people are most likely to benefit from CAPE supplementation based on current research?

Individuals with chronic inflammatory conditions, precancerous lesions, or high oxidative stress may benefit most from CAPE, as research shows its potency in suppressing NF-κB-driven inflammation and cancer cell proliferation. People with cardiovascular disease, metabolic syndrome, or autoimmune conditions are also candidates, given CAPE's dual anti-inflammatory and antioxidant mechanisms. However, those with active cancer treatment should consult healthcare providers before supplementing, as CAPE's effects on cancer cells may interact with conventional therapies.

### Does CAPE interact with immunosuppressant medications or blood thinners?

CAPE's potent NF-κB inhibition and antiplatelet properties warrant caution when combined with immunosuppressants (such as corticosteroids or biologics) or anticoagulants (warfarin, DOACs), as concurrent use may amplify immunosuppression or bleeding risk. Clinical interaction data in humans is sparse, so medical supervision is advised before combining CAPE supplements with these medication classes. Starting with lower doses and monitoring inflammatory markers or coagulation parameters is a prudent approach when concurrent use is necessary.

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