What are the natural sources of catechol?

November 22, 2025 •

4 min read

Catechol ($C_6H_4(OH)_2$) is a colorless organic compound found naturally in trace amounts within the plant kingdom. This article explores what are the natural sources of catechol and its related compounds, detailing its presence in common foods and its biological role.

Quick Summary

Catechol is an organic compound with two hydroxyl groups on a benzene ring, primarily found in plant-based sources like fruits, vegetables, and trees. It is also produced by microbial action and is a core component of larger molecules, notably the flavonoids known as catechins.

Key Points

Basic Structure: Catechol is a simple phenolic compound with a benzene ring and two adjacent hydroxyl groups.
Diverse Plant Sources: It is found in trace amounts in many plants, including certain fruits (apples, berries), vegetables (onions), and trees (oak, pine).
Key to Catechins: The catechol structure is a core component of larger flavonoid molecules called catechins, which are abundant in tea and cocoa.
Role in Enzymatic Browning: The browning reaction in fruits like apples and bananas is caused by the enzyme catechol oxidase, which oxidizes catechols.
Metabolic Precursor: The catechol backbone is essential for the structure of important neurotransmitters and hormones, such as dopamine and epinephrine.
Microbial Production: Certain bacteria can biosynthesize catechol from simpler compounds like glucose.
Distinction is Important: It is crucial to distinguish between the simple catechol molecule and the more complex and widely consumed catechins when discussing dietary sources.

Understanding the Catechol Structure

Catechol, also known as pyrocatechol or 1,2-dihydroxybenzene, is a phenolic compound characterized by a benzene ring with two hydroxyl (-OH) groups attached to adjacent carbon atoms. While the simple catechol molecule occurs in nature, it is more commonly found as a structural component within larger, more complex molecules. The most notable of these larger compounds are the catechins, a type of flavonoid. This distinction is crucial for understanding the presence of catechol in various natural sources, particularly dietary ones.

Plant and Dietary Sources of Catechol and its Derivatives

Fruits and Vegetables

Many common fruits and vegetables contain free catechol or its derivatives, often linked to the enzymatic browning process. This browning is caused by the enzyme catechol oxidase, which oxidizes catechol and other phenolic compounds when the plant tissue is damaged and exposed to oxygen.

Apples: Contains catechins and related polyphenols. When an apple is cut, the enzymatic browning reaction reveals the presence of these compounds.
Berries: Blackberries, strawberries, and other berries are rich in catechins.
Grapes and Wine: Both grapes and red wine are significant sources of catechins and other flavonoids incorporating the catechol structure.
Onions: This vegetable is noted as a dietary source of catechol.
Cocoa and Chocolate: Cocoa beans and dark chocolate are among the foods with the highest concentrations of catechins.
Peaches and Plums: These stone fruits also contain catechins.

Other Plant-Based Sources

Beyond common dietary items, catechol is found in a variety of other plants and derived products:

Tea: Green tea is particularly rich in catechin derivatives, such as epigallocatechin gallate (EGCG), which incorporate the catechol moiety. The fermentation process to make black tea alters these compounds.
Trees: Catechol occurs naturally in various trees, including pine, oak, and willow.
Beechwood Tar: Historically, catechol was isolated from beechwood tar.
Kino: A red, resinous extract from certain trees, especially those in the Pterocarpus genus, has been identified as a source of free catechol.
Poplar Buds and Propolis: Catechol is a marker compound found in poplar bud extracts, which bees collect to make propolis. The catechol is metabolized by bee enzymes, so it is typically not found in the final propolis product.

Biosynthesis and Metabolic Production

Catechol's presence in nature isn't limited to its free form or as part of larger plant compounds. It is also a key intermediate in the biosynthesis and metabolism of various organisms.

Microbial Biosynthesis: Certain bacteria can synthesize catechol from glucose or produce it as a byproduct during the degradation of more complex plant compounds. This occurs in the gut microbiome, where gut symbionts biotransform plant polyphenols.
Animal Metabolism: The catechol structure is a fundamental part of crucial animal neurotransmitters and hormones, collectively known as catecholamines. These include dopamine, norepinephrine, and epinephrine, which are synthesized from the amino acid tyrosine. While free catechol itself isn't a primary component, its structural skeleton is essential to these vital molecules.

Catechol vs. Catechins: A Comparative Look

It is important to differentiate between the simple compound catechol and the larger class of flavonoid antioxidants called catechins. This table clarifies the key differences.


Feature	Catechol ($C_6H_4(OH)_2$)	Catechins (Flavanols)
Chemical Structure	A simple benzene ring with two adjacent hydroxyl groups.	A more complex flavonoid structure that contains a catechol moiety.
Occurrence	Found in trace amounts, especially in trees and raw plant tissues.	Widespread and abundant in many foods, particularly tea, cocoa, and berries.
Biological Role	Can act as a substrate for enzymes like catechol oxidase and is a structural base for other compounds.	A class of potent antioxidants associated with various health benefits.
Dietary Source	Present in small amounts in some fruits and vegetables.	High concentrations are found in tea, red wine, cocoa, and various fruits.
Reactivity	Prone to oxidation, which is what causes enzymatic browning.	Exhibit antioxidant properties themselves, protecting cells from oxidative stress.

Conclusion

Catechol's natural presence is more complex than a simple list of dietary sources. While trace amounts of the basic compound are found in some plants and microbial processes, its significance in nature often lies in its role as a structural foundation. The much larger, flavonoid-based catechins are the primary way consumers encounter the catechol moiety in food. Understanding this nuance is key to appreciating its role in both food chemistry and biological processes. From the familiar browning of a cut apple to the potent antioxidants in green tea, catechol's chemical backbone is a widespread feature of the natural world. For more information on catechol's chemical properties, see the PubChem entry.

Further Research and Considerations

While natural sources provide small exposures to catechol, industrial production and environmental contamination are also factors. The majority of commercial catechol is synthetically manufactured for use in pesticides, perfumes, and other industrial products. This distinction is important for understanding the context of human exposure and its biological effects.

Frequently Asked Questions

Catechol is a simple, foundational organic molecule, while catechins are a larger, more complex class of flavonoid compounds that contain the catechol structure as part of their chemical makeup.

No. The catechol in foods is usually part of larger molecules like catechins. The health effects associated with these foods, such as green tea or cocoa, are due to the combined action of many compounds, not just the isolated catechol moiety.

A tell-tale sign of catechol oxidase activity, which acts on catechol derivatives, is enzymatic browning. If a fruit like an apple or banana turns brown when cut and exposed to air, it indicates the presence of these compounds.

While the larger, related catechins are well-regarded antioxidants with potential health benefits, isolated catechol is used for industrial purposes and can have toxic effects at high concentrations. Context and dosage are key.

To increase your intake of the catechol backbone via catechins, you can consume more green tea, cocoa, berries, and apples. Focus on these flavonoid-rich foods rather than seeking isolated catechol.

The human body produces catecholamine neurotransmitters, such as dopamine, which have a catechol structure. These are synthesized from the amino acid tyrosine, not directly from ingested catechol.

Yes, catechol can be produced by certain bacteria. Some microbes in the gut can synthesize catechol from glucose or as a byproduct of breaking down other plant compounds.

Bees collect plant matter containing catechol from poplar buds to make propolis. However, bee enzymes metabolize the catechol during this process, so it is generally absent in the finished propolis product.