Ellagitannin

Ellagitannins, also known as ellagtannins, are a diverse class of hydrolyzable tannins of plant polyphenols and tannins formed by oxidative linkage of gallic acids, primarily in 1,2,3,4,6-pentagallylglucose. They are found in some fruits, nuts and seeds, such as pomegranates, black raspberries, raspberries, strawberries, walnuts and almonds (Landete JM 2011).

Ellagitannins differ from gallotannins in that their galloyl groups are linked by C-C bonds, whereas the galloyl groups in gallotannins are linked by depside bonds. Ellagitannins generally form macrocycles, whereas gallotannins do not. Biosynthesis of ellagitannins occurs via 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose by a laccase-like phenol oxidase to form tellimagrandin II, followed by further oxidation by another phenol oxidase to form cornusiin E (a dimeric ellagitannin). Ellagitannins are hydrolyzed under physiological conditions in vivo to ellagic acid, which is then gradually metabolized by the gut microbiota to form various types of urolithins.

More than 1000 ellagitannins have been described. Examples of ellagitannins include: Castalagin, Castalin, Casuarictin, Casuarinin, Castanopsinins A to H, Excoecarianin, Grandinin, Pterocarinins A and B, Rhoipteleanins A to G, Roburin A, Tellimagrandin II, Terflavin B, Punicalagin, Punicalin, Punigluconin, Alnusiin, Alnusnin A, Alnusnin B, Cercidinin A, Cercidinin B, Chebulagic acid, Chebulinic acid, Corilagin, Geraniin, Isoterchebin, Nobotanins B, C, E, G, H, I, J, and K, Roxbin B, Sanguiins H-2, H-3, and H-6, Stachyurin, Terchebin, Vescalagin, and Vescalin. They are found mainly in dicotyledonous angiosperms, such as myrtales, which include the pomegranate

An antiproliferative and apoptosis-inducing effect of EA and urolithins has been demonstrated. The results of clinical, interventional and animal in vivo studies clearly indicate the anti-inflammatory potential of HT-containing products as well as of pure ellagitannins and gallotannins. This concerns their postulated efficacy in inflammatory bowel disease (IBD) and cardiovascular disease (Kiss AK et al. 2018; Landete JM 2011).

Castalagin is an ellagitannin found in oak and chestnut wood and in the stem barks of Anogeissus leiocarpus and Terminalia avicennoides. Castalagin/vescalagin are the most abundant ellagitannins in white wine aged in oak barrels. As the wines age, these two compounds are gradually extracted from the wood and transformed into new derivatives through chemical reactions. Therefore, castalagin/vescalagin and their derivatives contribute to the colour and flavour of wines and spirits stored in oak barrels (Marinov M G 1997).

1. Feldman KS et al (2003) Ellagitannin chemistry. Studies on the stability and reactivity of 2,4-HHDP-containing glucopyranose systems. In: The Journal of organic chemistry 68: 7433-7438.
2. Kiss AK et al. (2018) Ellagitannins, Gallotannins and their Metabolites- The Contribution to the Anti-Inflammatory Effect of Food Products and Medicinal Plants. Curr Med Chem 25: 4946-4967.
3. Landete JM (2011) Ellagitannins, ellagic acid and their derived metabolites: A review about source, metabolism, functions and health. Food Research International 44: 1150-1160
4. Marinov M G (1997) Kinetics of ellagitannin extraction from oak wood using white wine. Journal of Wine Research 8: 29-40.