Chemical functionalization of polysaccharides with aromatic molecules: A 1H NMR spectrum is not always enough for confirming the derivatization

Carbohydrate-aromatics interactions are well known in Nature and are also exploited in food and pharmaceutical industry for encapsulating low molecular weight drugs or flavors into polysaccharide carriers. Despite that, the non-covalent entrapment of small molecules containing aromatic moieties into the 3D-structure of a poly-saccharide is typically overlooked in the context of the structural characterization of derivatized polysaccharides, that is often limited to the measurement of only 1H NMR spectra. This study demonstrates that it can be misleading in some cases. We report some examples of products – obtained by grafting polysaccharides with small molecules containing aromatic moieties and displaying fully satisfying 1H NMR spectra – that were demonstrated to be instead poorly or even not derivatized at all by 2D-NMR analysis. Although these results do not question any polysaccharide grafting with aromatic functionalities reported so far in literature, they strongly support the necessity of a structural characterization based not merely on 1H NMR spectra for a robust demonstration of a successful polysaccharide derivatization.