Catechins

Catechins are a group of natural polyphenolic compounds belonging to the flavanol family, a subclass of flavonoids. They are widely studied for their antioxidant properties and are found in a variety of plants. The term covers several closely related molecules, including catechin, epicatechin, gallocatechin, epigallocatechin, and their gallic acid esters such as catechin gallate, epicatechin gallate, and especially epigallocatechin gallate (EGCG), which is the most abundant in green tea.

Primary sources and occurrence vary with processing. Green tea leaves contain high levels of catechins, particularly EGCG. Catechins are also present in cocoa, apples, berries, grapes, and other fruits. During fermentation or oxidation of tea leaves, some catechins are transformed into theaflavins and thearubigins, altering the catechin profile in black tea.

Biochemistry and metabolism. Catechins act as antioxidants by scavenging free radicals and modulating cell signaling pathways. They can influence enzyme activity, gene expression, and inflammatory responses in laboratory studies. After ingestion, catechins are absorbed in the small intestine, undergo conjugation in the liver, and are excreted in urine; gut microbiota further transform them into smaller phenolic compounds.

Health considerations. Evidence from human studies suggests potential benefits for cardiovascular and metabolic health, but results are mixed and not definitive. They are generally considered safe at typical dietary intakes; however, high-dose catechin extracts may cause adverse effects in rare cases and can interfere with non-heme iron absorption. Catechins are also used as natural antioxidants in foods and beverages and are studied for their roles in disease prevention, though robust clinical guidance remains limited.