2D DOSY NMR: A Valuable Tool to Confirm the Complexation in Drug Delivery Systems.

Many bioactive substances face the problem of limited bioavailability, mainly due to low aqueous solubility and poor metabolic stability. Their complexation with drug delivery systems offers a more optimum pharmacological profile. Some of these drug delivery systems that have promising potential form complexes with bioactive compounds such as cyclodextrins and calixarenes. The monitoring of the success and the type of the complexation are of great importance and two-dimensional diffusion-ordered NMR spectroscopy (2D DOSY) is a valuable tool for the studying of these complexes and described as "NMR chromatography." Herein we report the procedure for the complexation of the natural product quercetin in 2-hydroxypropyl-β-cyclodextrin and the anticancer drug temozolomide in p-sulfonatocalix[4]arene and the determination of the complexation with 2D DOSY spectroscopy.