CINNAMIC ACID: STRUCTURE, PROPERTIES, PRODUCTION, USES - CHEMISTRY - 2025

The cinnamic acid is an organic compound whose chemical formula is C ₆ H ₅ CHCHCOOH. It is a monocarboxylic acid. Its name comes from the Cinnamomum cassia plant, whose bark is aromatic like that of the cinnamon plant.

Other names are 3-phenyl-2-propenoic acid and β-phenyl acrylic acid. Many derivatives of cinnamic acid have been obtained, which exhibit therapeutic properties.

Cinnamomum cassia plant. Honmingjun. Wikipedia Commons.

Due to the C = C double bond, the cinnamic acid molecule has two isomers: cis and trans. The trans form is the most abundant in nature. Trans cinnamic acid is a constituent of the essential oils of cinnamon, basil, black tea tree or Melaleuca bracteata, cocoa, Tolu balsam, greater galangal or Alpinia galanga and storach leaves. Cis cinnamic acid has been found in the Alpinia malaccensis plant.

In the late 19th and early 20th centuries, cinnamic acid was studied and used to treat various diseases. However, its use was discontinued and research was resumed a few years ago, generating promising results.

Structure

The cinnamic acid molecule contains a phenyl group, a propenyl (propane with a C = C double bond) and a carboxyl -COOH group attached to the latter. It is like an acrylic acid with a phenyl group on the third carbon.

Due to its double bond, the molecule can be in the cis form or the trans form. In the trans form, the C ₆ H ₅ - and -COOH groups are found diagonally opposite the C = C double bond. In the cis form these groups are on the same side (one on each carbon of the C = C double bond).

Isomers of cinnamic acid. Author: Marilú Stea.

Nomenclature

- Cinnamic acid

- 3-phenyl-2-propenoic acid

- β-phenyl acrylic acid

- Benzenepropenoic acid

- Benzeneacrylic acid

Properties

Physical state

White crystalline solid with monoclinic prism structure.

Cinnamic acid Aleksander Sobolewski via Wikimedia Commons. Source: Wikipedia Commons.

Molecular weight

148.16 g / mol

Melting point

Cis isomer: 68 ºC

Trans isomer: 133 ºC

Boiling point

Cis isomer: 125 ° C at 19 mm Hg

Trans isomer: 300 ºC

Solubility

Weakly soluble in water: 0.546 g / L at 25 ºC.

Very soluble in ether.

Chemical properties

The cinnamic acid molecule has three reactive sites: substitution in the benzene ring, addition in unsaturation (C = C double bond) and reaction of the carboxyl group –COOH.

This allows many derivatives to be obtained from cinnamic acid, which has generated special interest from researchers, especially in the field of medicine.

The presence of a benzene ring in its molecule and the unsaturated short chain make it have low polarity, hence its low solubility in water.

Cinnamic acid salts or alkali metal cinnamates are soluble in water.

Role in nature

Cinnamic acid has a particular role in the metabolism of plants, as it is distributed throughout the entire plant kingdom.

Cinnamon bark. Thiry. Source: Wikipedia Commons.

It is a precursor of flavonoids, alkaloids, coumarins and lignin, a structural component of plants.

It belongs to the class of auxins, which are hormones that regulate cell growth in plants.

Obtaining

In nature, the trans isomer of cinnamic acid comes from the removal of ammonia from phenylalanine (an amino acid), which occurs thanks to the enzyme phenylalanine-ammonia-lyase. This enzyme is found in higher plants, fungi, and yeasts.

Cinnamic acid is often conjugated with amino acids and sugar acids. For example, cinnamoglycine is present in plants, but could be a product of animal metabolism. It is found in the scent gland of the Canadian beaver, but you likely get it from food.

Use in medical applications

Anti-cancer effect

Cinnamic acid has been used for hundreds of years for the treatment of cancer in Chinese medicine, as it is part of the Xuanshen, which is the root of a herbaceous plant of the Scrophulariaceae family.

In the late 19th and early 20th centuries it was used to treat cancer, but research was not continued until a few decades ago.

Although its role is unknown, its effectiveness against bone cancer (osteosarcoma) has recently been confirmed.

It was also found to exert an antiproliferation effect on malignant cells of colon adenocarcinoma, melanoma, prostate cancer and lung cancer.

According to some experiences, treating melanoma cells with cinnamic acid for 3 days resulted in a 75-95% loss of invasiveness, that is, the ability to degrade and cross the tissue barrier. This is attributed to the modulation it exerts on the genes involved in tumor metastasis.

Furthermore, cinnamic acid has been found to be a potent inhibitor of an enzyme that influences the progression of hormone-dependent forms of cancer, such as prostate, breast, and endometrial cancer.

In addition, countless compounds derived from cinnamic acid have anticancer properties.

Positive effects against insulin resistance and diabetes

Some researchers found that cinnamic acid can alleviate insulin resistance.

This disease consists of the non-effectiveness of the action of insulin or the inability for it to achieve a normal response of glucose absorption by the cells.

Due to this, the cells do not absorb glucose, which remains in the blood and hyperglycemia or excess glucose in the blood occurs. The cell is then said to be resistant to insulin.

The consequence of not treating insulin resistance is type 2 diabetes.

Cinnamic acid has mechanisms of action that improve the effectiveness of insulin, which translates into increased glucose uptake by insulin-resistant cells and disease relief.

Several polyphenolic derivatives of cinnamic acid are also beneficial in treating these diseases, but due to their low bioavailability, both cinnamic acid and its derivatives are still under study.

Efforts are being made to develop various forms of administration of these compounds, such as nanoparticles, encapsulation and emulsions.

Anti-tuberculosis effects

Trans-cinamic acid and its derivatives were used as anti-tuberculosis agents around 1894. However, they have only recently been re-studied for this purpose.

Currently they have been found to have a synergistic effect when used with other antituberculous drugs, even those to which the Mycobacterium tuberculosis bacteria have become resistant, repowering the action of the drug.

Mycobacterium tuberculosis. Photo Credit: Janice CarrContent Providers (s): CDC / Dr. Ray Butler; Janice Carr. Source: Wikipedia Commons.

Various beneficial effects

Cinnamic acid and many of its derivatives exhibit hepatoprotective, antimalarial, antioxidant and protective activity on the cardiovascular system.

Also many of its polyphenolic derivatives exert antibacterial, antiviral and antifungal effects.

Use in the food industry

Cinnamic acid and several of its derivatives are used to flavor some foods.

For cinnamic acid in particular the daily intake limit, or ADI (Acceptable Daily Intake), according to Council of Europe standards is 1.25 mg / kg per day.

New applications

Recently (2019) it was found that cis -cinamic acid favors the growth of the Arabidopsis thaliana plant, which is a relative of cabbage and mustard.

The scientists concluded that cis -cinamic acid has a high potential as a plant growth promoting agrochemical.

References

1. Hoskins, JA (1984). The Occurrence, Metabolism and Toxicity of Cinnamic Acid and Related Compounds. Journal of Applied Toxicology, Vol. 4, No. 6, 1984. Retrieved from onlinelibrary.wiley.com.
2. US National Library of Medicine. (2019). Cinnamic acid. Recovered from: pubchem.ncbi.nlm.nih.gov.
3. Huang, D.-W. et al. (2009). Effect of Caffeic Acid and Cinnamic Acid on Glucose Uptake in Insulin-Resistant Mouse Hepatocytes. Agric. Food Chem. 2009, 57, 7687-7692. Recovered from pubs.acs.org.
4. De, P. et al. (2011). Cinnamic Acid Derivatives as Anticancer Agents - A Review. Current Medicinal Chemistry, 2011, 18, 1672-1703. Recovered from eurekaselect.com.
5. De, P. et al. (2012). Cinnamic Acid Derivatives in Tuberculosis, Malaria and Cardiovascular Diseases - A Review. Current Organic Chemistry, 2012, 16, 747-768. Recovered from eurekaselect.com.
6. Sova, M. (2012). Antioxidant and Antimicrobial Activities of Cinnamic Acid Derivatives. Mini-Reviews in Medicinal Chemistry, 2012, 12, 749-767. Recovered from ncbi.nlm.nih.org.
7. Adisakwattana, S. (2017). Cinnamic Acid and Its Derivatives: Mechanisms for Prevention and Mangement of Diabetes and Its Complications. Nutrients 2017, 9, 163. Recovered from ncbi.nlm.nih.gov.
8. Steenackers, W. et al. (2019). cis -Cinnamic acid is a natural plant growth-promoting compound. Exp. Bot. 2019 Aug 30. Recovered from ncbi.nlm.nih.gov.