Ellagitannin

The ellagitannins are a diverse class of hydrolyzable tannins, a type of polyphenol formed primarily from the oxidative linkage of galloyl groups in 1,2,3,4,6-pentagalloyl glucose. Ellagitannins differ from gallotannins, in that their galloyl groups are linked through C-C bonds, whereas the galloyl groups in gallotannins are linked by depside bonds.^[1]

Castalagin is a representative ellagitannin, characterized by coupled gallic acid substituents

Ellagitannins contain various numbers of hexahydroxydiphenoyl units, as well as galloyl units and/or sanguisorboyl units bounded to sugar moiety. In order to determine the quantity of every individual unit, the hydrolysis of the extracts with trifluoroacetic acid in methanol/water system is performed. Hexahydroxydiphenic acid, created after hydrolysis, spontaneously lactonized to ellagic acid, and sanguisorbic acid to sanguisorbic acid dilactone, while gallic acid remains intact.^[2]

Ellagitannins generally form macrocycles, whereas gallotannins do not.

Examples

• Castalagin
• Castalin
• Casuarictin
• Grandinin
• Oenothein B from Willowherbs (Epilobium spp.)
• Roburin A
• Tellimagrandin II
• Terflavin B
• Vescalagin
• Pomegranate ellagitannins, many compounds
  • Punicalagin
  • Punicalin

Metabolism

Degradation

Urolithins, such as urolithin A, are microflora human metabolites of dietary ellagic acid derivatives.^[3]

Natural occurrences

Ellagitannins are reported in dicotyledoneous angiospermes, and notably in species in the order Myrtales, such as the pomegranate.^[4][5]

See also

• Urolithin - Urolithin A
• Polyphenols
• List of antioxidants in food

Other links

• MALDI-TOF Mass Spectrometric Analysis of Hydrolysable Tannins