TWO ELLAGITANNINs

Ellagitannins (a class of secondary metabolites) are a type of polyphenols characterised by biaryl-linked Galloyl groups (from Gallic Acid) which are esterified to a glucose core. They are found in tea and the wood of trees, especially hardwoods, and are toxic to micro-organisms, helping to preserve the wood. Ellagitannins are brownish. There are literally hundreds of differing ellagitannins, for the galloyl groups can combine in many different ways with the glucose units and with each other, so many that your author cannot possibly show even a fraction of them.

Ellagic Acid is a condensation dimer of Gallic Acid. The two Gallic Acid groups have been coloured differently, for easy identification, in red and blue. Elements of the dimer that are common to both are shown in black. Plants produce Ellagic Acid before converting it to ellagitannins. The highest levels of Ellagic Acid are to be found in the fruits of Strawberry, Cranberry, Raspberry and Grape. It too possesses anti-oxidant properties. It also inhibits the binding of certain carcinogens such as Nitrosamines and Polycyclic aromatic hydrocarbons (PAHs) to DNA, but trials of its use in treating prostate cancer have so far proved negative, but this has not stopped certain dietary supplement manufacturers from making illegal exaggerated claims of supposed benefits.

Potentillin is a monomeric ellagitannin and has an α-glycosyl linkage. It consists of a glucose molecule (shown in red). Surrounding the glucose unit are four more Gallic Acid moieties (galloyl groups, shown in blue, apart from the hydroxyl groups). The galloyl groups are also linked together in pairs, apart from a lone one on the right. Potentillin has been found in Japanese Agrimony (Agrimonia japonica) and in Strawberry.

It is interesting to note that Pedunculagin, another monomeric ellagitannin with one less galloyl group than Potentillin, is also found in many members of the same plant family. Pedunculagin exhibits anti-bacterial activity against Helicobacter pylori.

It can be seen that Agrimoniin is another ellagitannin and is a dimer of two Potentillin molecules. Agrimoniin consisting of two identical Potentillin molecules fused together by an oxygen bridge (central red 'O'). Your author has had to bend the molecule slightly in order to more clearly show the near bi-lateral symmetry (the way that oxygen bridge links the two identical units is the only part that is asymmetrical).