4-Methoxycinnamic acid
[CAS# 830-09-1]

Identification

• Classification: Flavors and spices >> Synthetic spice >> Aromatic cinnamic acid, esters and derivatives
• Name: 4-Methoxycinnamic acid
• Synonyms: trans-4-Methoxycinnamic acid; p-Methoxycinnamic acid; 3-(4-Methoxyphenyl)-2-propenoic acid
• Molecular Formula: C₁₀H₁₀O₃
• Molecular Weight: 178.19
• CAS Registry Number: 830-09-1
• EC Number: 212-594-0
• SMILES: COC1=CC=C(C=C1)/C=C/C(=O)O

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*
• Melting point: 173.5 - 174 ºC (Expl.)
• Boiling point: 342.6±17.0 ºC 760 mmHg (Calc.)^*
• Flash point: 138.6±14.4 ºC (Calc.)^*
• Index of refraction: 1.591 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: Pictogram(s)
• Risk Codes: R36/37/38
• Safety Description: S26;S37/39

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335

Discovory and Applicatios

4-Methoxycinnamic acid, also known as para-methoxycinnamic acid, is a naturally occurring derivative of cinnamic acid, a compound widely distributed in plants. Its structure is characterized by a phenyl ring bearing a methoxy substituent at the para position and a propenoic acid side chain, giving it the molecular formula C₁₀H₁₀O₃. This compound was first identified as one of the minor phenolic constituents in plant extracts, particularly in species known for producing cinnamic acid derivatives as part of their secondary metabolites. The presence of this molecule in natural sources is related to the phenylpropanoid pathway, a central metabolic route in plants responsible for generating a wide variety of aromatic compounds involved in structural, defensive, and signaling roles.

The discovery of 4-methoxycinnamic acid in plants was important because it contributed to the broader understanding of how plants modify cinnamic acid through enzymatic substitutions, such as hydroxylation and methylation, to produce molecules with specific biological activities. Compounds of this type were investigated for their role in plant defense against pathogens and ultraviolet radiation. The para-methoxy substituent in 4-methoxycinnamic acid enhances its light-absorbing properties, making it effective at dissipating potentially harmful ultraviolet radiation, which may explain why many plants incorporate similar cinnamate derivatives as part of their protective biochemical arsenal.

From the early stages of its isolation, attention turned to its potential applications. In organic chemistry, 4-methoxycinnamic acid became a valuable intermediate for synthesizing esters and other derivatives. Through esterification, a series of molecules with significant commercial importance were developed. Among these, octyl methoxycinnamate emerged as one of the most widely used UVB filters in sunscreen formulations. This derivative, obtained by combining 4-methoxycinnamic acid with 2-ethylhexanol, demonstrates strong absorption in the UVB range of 280–320 nm, providing protection against sunburn and related skin damage. Its introduction into personal care products marked one of the most significant industrial applications of a cinnamic acid derivative, with regulatory approval in many countries confirming its safety and effectiveness when used within established limits.

Pharmaceutical research has also explored 4-methoxycinnamic acid and its derivatives due to their pharmacological potential. Several studies reported that cinnamic acids with methoxy substituents exhibit antimicrobial and antioxidant activities. These properties suggested possible applications as lead structures in drug discovery, particularly for conditions in which oxidative stress plays a pathogenic role. Derivatives prepared from 4-methoxycinnamic acid have been investigated for anti-inflammatory effects, with certain analogs showing measurable activity in laboratory models. While the parent compound itself has not been developed into a widely marketed drug, its contribution lies in providing a chemical scaffold that can be modified to enhance biological activity.

In addition to medicine and cosmetics, 4-methoxycinnamic acid has relevance in the fragrance and flavor industry. The aromatic ring and conjugated double bond system confer a characteristic odor profile that can be exploited in the preparation of synthetic fragrances. Its esters and related compounds are incorporated into formulations where both olfactory quality and stability under light exposure are desirable. Moreover, as part of the larger family of cinnamic acid derivatives, it has been used to improve the shelf life of foods through antioxidant properties, thereby linking it to applications in food preservation.

The preparation of 4-methoxycinnamic acid in the laboratory is generally achieved through the Knoevenagel condensation of 4-methoxybenzaldehyde with malonic acid, a reaction that allows efficient construction of the propenoic acid side chain. This synthetic route has been widely employed because it yields cinnamic acids with predictable substitution patterns. Advances in green chemistry have also introduced alternative methodologies, including solvent-free and catalyst-assisted procedures, reflecting ongoing interest in sustainable synthesis of this versatile compound.

Overall, 4-methoxycinnamic acid represents a significant example of how a relatively simple plant-derived compound can serve as a cornerstone for industrial, pharmaceutical, and cosmetic applications. Its discovery in natural sources not only deepened the understanding of plant secondary metabolism but also provided a platform for the development of UV filters, bioactive molecules, and fragrances. Today, its importance is evident both as a natural product and as a synthetic intermediate with established roles in several industries.

References

2023. New Europium Methoxycinnamates: Synthesis and Thermal and Luminescence Properties. Russian Journal of General Chemistry.
DOI: 10.1134/s1070363223100092

2024. Effect of kefiran- guar gum-based edible coating infused with Murraya koenigii berry extract on quality of button mushroom (Agaricus bisporus) during postharvest storage. Journal of Food Measurement and Characterization.
DOI: 10.1007/s11694-024-02645-0

2025. Enhancing Malva sylvestris extract properties through lactic acid bacteria fermentation: impact on phytochemical profile and bioactivity. Food Production, Processing and Nutrition.
DOI: 10.1186/s43014-025-00315-2