Flavonoid mixture analysis by matrix-assisted diffusion-ordered spectroscopy.

The structural similarity of flavonoids, often present in natural product mixtures, makes their analysis by NMR methods less than straightforward. This similarity is a dual problem for one of the most powerful NMR methods for mixture analysis, diffusion-ordered spectroscopy (DOSY), which relies both on well-resolved peaks and on differences in hydrodynamic radii for separating the signals from different components in a mixture. To overcome these limitations, we use a matrix-assisted DOSY approach that exploits differential chemical interactions with a slow diffusion matrix (here micellar sodium dodecyl sulfate) to resolve flavonoid mixtures in mixed solvents.