ellagitannins

Ellagitannins are a class of hydrolyzable tannins defined by hexahydroxydiphenoyl (HHDP) groups esterified to a sugar, typically glucose. They can be monomeric or polymeric, with HHDP units linked in various ways to form a diverse range of structures. When hydrolyzed, the HHDP units are released and commonly lactonize to ellagic acid, yielding ellagic acid derivatives and other breakdown products. The structural complexity of ellagitannins underpins their biological and sensory properties.

Ellagitannins occur widely in the plant kingdom and are especially abundant in pomegranate (rinds and juice), berries (such as strawberries and raspberries), walnuts, pecans, and oak wood. They are also found in certain wines and teas. Common examples include punicalagin and punicalin from pomegranates and pedunculagin from various fruits. In foods they contribute astringency and may influence color and antioxidant capacity due to their polyphenolic nature.

In the body, ellagitannins are not readily absorbed in the small intestine; they are largely metabolized by the gut microbiota to urolithins, which can be absorbed and may exert biological effects. In vitro and animal studies have reported antioxidant, anti-inflammatory, antimicrobial, and potential anti-cancer activities, but human evidence remains inconclusive. Ellagitannins can also bind proteins and minerals, which can affect digestibility and mineral absorption. As a group, they are a focus of research in nutrition, food science, and phytochemistry for their health-related potential and functional properties in foods.