Gallotannins and Tannic Acid: First Chemical Syntheses and In Vitro Inhibitory Activity on Alzheimer's Amyloidβ-Peptide Aggregation.
Angew Chem Int Ed Engl. 2015 Jul 6 ;54(28):8217-21. Epub 2015 May 26. PMID: 26013280
The screening of natural products in the search for new lead compounds against Alzheimer's disease has unveiled several plant polyphenols that are capable of inhibiting the formation of toxicβ-amyloid fibrils. Gallic acid based gallotannins are among these polyphenols, but their antifibrillogenic activity has thus far been examined using"tannic acid", a commercial mixture of gallotannins and other galloylated glucopyranoses. The first total syntheses of two true gallotannins, a hexagalloylglucopyranose and a decagalloylated compound whose structure is commonly used to depict"tannic acid", are now described. These depsidic gallotannins and simpler galloylated glucose derivatives all inhibit amyloidβ-peptide (Aβ) aggregation in vitro, and monogalloylated α-glucogallin and a natural β-hexagalloylglucose are shown to be the strongest inhibitors.