NMR studies of dextran oligomer interactions with model polyphenols

The interaction of bacterial dextrans with polyphenols has been implicated in the formation of dental plague. Therefore, the NMR spectra of the (1 → 6)-α-linked dextran oligomers, (glucose)n(n = 1, 2, 3, >3), have been assigned using two-dimensional methods. Addition of a model polyphenol, propyl gallate, causes only very small changes in the NMR chemical shifts of isomaltose (n = 2) and polymers of average length up to 8.2, indicating little apparent binding under these conditions. Titration of dextrans with a model nonhydrolysable proanthocyanidin tannin, (−)-epicatechin, produced no significant chemical shift changes. These results suggest that the function of bacterial dextrans in modulating the polyphenol content of plaque is at most indirect.