Cinnamic Acid (Phenylpropanoid · Antifungal · Anti-inflammatory)

Compound	Cinnamic Acid (Trans-Cinnamic Acid)
Chemical class	Polyphenol — Phenylpropanoid (3-Phenyl-2-propenoic Acid)
CAS	140-10-3
Primary source	Cinnamomum verum / C. cassia (cinnamon bark), Styrax spp.
Key applications	Antifungal, antimicrobial, anti-inflammatory, flavouring agent
Claim strength	Moderate
Typical form	Cinnamon bark extract co-constituent; cinnamon essential oil component
Buy from Herbuno	Cinnamon Extract Powder - Cinnamomum verum →

Name origin: Directly from cinnamon — the spice from which it was first characterised. Cinnamic acid is the simplest phenylpropanoid acid — a phenyl ring attached to an α,β-unsaturated carboxylic acid (propenoic acid) chain. It is the biosynthetic precursor to all hydroxycinnamic acids (caffeic, ferulic, p-coumaric, sinapic) and forms the basis of the entire phenylpropanoid pathway in plants. Traditional use: Cinnamon bark preparations have extensive traditional use across South Asian, Chinese, and Middle Eastern medical traditions for blood sugar regulation, digestive complaints, respiratory infections, and antimicrobial applications. Cinnamic acid is a key constituent alongside cinnamaldehyde, procyanidins, and eugenol. Research trajectory: Trans-cinnamic acid has documented antifungal, antimicrobial, anti-inflammatory, and modest antidiabetic activity in preclinical research. Clinical evidence for the isolated compound is limited; most cinnamon clinical data involve the complex extract. Commercial source: Co-delivered via cinnamon bark extract and cinnamon powder. See sourcing options below.

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Evidence for Cinnamic Acid Applications

Antifungal and antimicrobial: Trans-cinnamic acid demonstrates antifungal activity against Candida albicans, Aspergillus, and food-borne moulds at MIC values of 0.5–2 mg/mL, and antibacterial activity against S. aureus, E. coli, and Listeria. Mechanism involves cell membrane disruption and inhibition of ergosterol biosynthesis in fungi. Relevant for natural antimicrobial formulations and food preservation. Claim strength: Moderate.

Anti-inflammatory: Cinnamic acid inhibits NF-κB and reduces COX-2 expression in cell models. Structural studies show the α,β-unsaturated carboxylic acid Michael acceptor system contributes to covalent interaction with inflammatory kinases. Anti-inflammatory potency is moderate compared to hydroxycinnamic acid counterparts. Claim strength: Moderate.

Antidiabetic: Cinnamic acid stimulates insulin secretion from pancreatic β-cells via GLP-1 pathway modulation in animal models, and reduces α-glucosidase activity. Relevant as a co-contributor to cinnamon extract’s documented antidiabetic effects alongside procyanidins and methylhydroxychalcone polymer (MHCP). Claim strength: Moderate.

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Dosage & Formulator Specification

No established isolated cinnamic acid supplement dose. Cinnamon extract clinical trials: 1–6 g/day whole cinnamon or 120–360 mg/day cinnamon extract (20% polyphenols) for blood glucose management. Cinnamic acid content in commercial cinnamon extract varies; request HPLC quantification alongside cinnamaldehyde and procyanidin content for comprehensive extract characterisation.

Note: coumarin content is a quality and safety consideration for cinnamon extracts. C. cassia (Cassia cinnamon) contains significant coumarin (up to 5 g/kg in bark); C. verum (Ceylon cinnamon) has much lower coumarin (<0.02 g/kg). For products with high daily cinnamon intake, specify C. verum (Ceylon/True cinnamon) or verify coumarin levels are within EFSA safe intake limits (0.1 mg/kg body weight/day).

Cinnamic acid has low aqueous solubility (logP ~1.9). In cinnamon preparations, it is typically present as free acid or in esterified forms. Cinnamic acid itself is a GRAS-listed flavouring agent and food additive in many markets, simplifying its regulatory positioning in functional food and supplement applications.

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Frequently Asked Questions — Cinnamic Acid

Is cinnamic acid the same as cinnamaldehyde?
No. Cinnamic acid (3-phenyl-2-propenoic acid) and cinnamaldehyde (3-phenyl-2-propenal) are structurally related — cinnamaldehyde is the aldehyde and cinnamic acid is the corresponding carboxylic acid from the same phenylpropanoid precursor. Cinnamaldehyde is the primary volatile aroma compound in cinnamon (responsible for cinnamon flavour/smell) and has potent antimicrobial and TRPA1-activating activity. Cinnamic acid is less volatile, less pungent, and has somewhat different pharmacological properties.

What is the coumarin safety concern with cinnamon products?
Coumarin (not to be confused with coumaric acid) is a hepatotoxic lactone found in high concentrations in Cinnamomum cassia (Chinese/Vietnamese cinnamon) but negligible amounts in C. verum (Ceylon cinnamon). EFSA has set a tolerable daily intake of 0.1 mg coumarin/kg body weight/day. At high cinnamon supplement doses from cassia sources, coumarin exposure can approach this limit. Formulators should specify Ceylon cinnamon or verify coumarin levels when label dose exceeds approximately 2 g/day cassia cinnamon equivalent.

Is cinnamic acid a Michael acceptor and does this create any reactivity concerns?
Trans-cinnamic acid has a Michael acceptor α,β-unsaturated carbonyl system, which theoretically can react with biological nucleophiles (thiols, amines). In practice, cinnamic acid’s Michael acceptor reactivity is significantly lower than more electrophilic analogues (cinnamaldehyde, methyl cinnamate) at physiological pH and concentrations. Its documented safety as a food additive at typical use levels confirms that Michael acceptor reactivity is not a practical safety concern at conventional supplement doses.

Can cinnamon extract be used for both blood glucose and antimicrobial formulations?
Yes — cinnamon extract’s multi-mechanism profile (procyanidins for insulin sensitisation + cinnamaldehyde and cinnamic acid for antimicrobial + cinnamic acid for glucose transport) supports positioning in both metabolic health and oral antimicrobial supplement contexts. The same extract serves both applications; formulation intent and label claims must be defined for regulatory compliance.

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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