Structural features of hydrolysable tannins determine their ability to form insoluble complexes with bovine serum albumin

The ability of 32 purified and characterized hydrolysable tannins to form insoluble complexes with model protein bovine serum albumin was investigated with a turbidimetric 96-well plate reader method. The results showed clear relationship between the hydrolysable tannin structure and the intensity of haze that formed during the tannin–protein -complexation. In addition to molecular weight, structural features such as number of galloyl groups, degree of oxidative coupling between the galloyls, positional isomerism and cyclic vs acyclic glucose core were the major structural features that affected the ability of the monomeric hydrolysable tannins to form insoluble complexes with bovine serum albumin. While oligomers were superior to monomers in their capability to precipitate the model protein, their activity depended less on the functional groups, but mostly on their size and overall flexibility. These results allowed to construct an equation that predicted the protein precipitation capacity of the studied...