Structure and oligomers distribution of commercial Tara (Caesalpina spinosa) hydrolysable tannin
Résumé
Solvent extracted commercial Tara tannin extract have been examined by Matrix Assisted Laser Desorption/Ionisation Time-of-Flight (MALDI-TOF) mass spectrometry and by High Pressure Liquid Chromatography (HPLC). The Tara extract has been found to be composed of a series of oligomers of polygallic acid attached by an ester link to one quinic acid. They constitute the oligomers in higher proportion in the extract. Other polygallic chains linked to one only or two repeating units such as caffeic acid and methylated quinic, methylated gallic and methylated caffeic acids are also present. Negative ion mode MALDI-TOF showed that some carbohydrate residues appear to still be present, linked to the polyphenolic material of the extract but their proportion is very low as would be expected of a solvent extracted tannin.
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