12 Review: Cyclodextrin Inclusion Complexes Probed by NMR Techniques Francisco B. T. Pessine, Adriana Calderini and Guilherme L. Alexandrino Department of Physical Chemistry, Chemistry Institute, State University of Campinas Brazil 1. Introduction Cyclodextrins (CDs) are cyclic oligomers of glucopyranose units that play an important role as a host in inclusion complexes, where non-covalent interactions are involved. They have been extensively studied in supramolecular chemistry. Because of its biocompatibility, relatively non-toxicity and relatively low price, CDs have been widely employed for encapsulation of several substances, being used in food, cosmetic and pharmaceutical industries. Nuclear Magnetic Resonance spectroscopy (NMR) is one of the most useful techniques to study interactions of cyclodextrins with guest compounds. It is relatively easy to apply, the experiments are fast and it is the only technique that provides information on the right orientation of the guest molecule inside the cavity and also on other important parameters related to the physico-chemical characteristics of the inclusion complexes. In this review, it will be discussed the study of inclusion complexes between drugs and cyclodextrins by different NMR techniques. Initially, a brief introduction of the properties of cyclodextrins, its importance as innovative drug carrier systems and its applicability is reviewed. Then different NMR techniques used for characterization of inclusion complexes are detailed, with examples studied in our group, which involves since simple measures of 1 H-NMR spectrum to more sophisticated experiments, e.g. Diffusion Ordered SpectroscopY (DOSY), NOE methods (ROESY), T1 measure and solid NMR by 13 C Cross-Polarization Magic Angle Spinning (CPMAS). 2. Properties of cyclodextrins Cyclodextrins (CDs) as complexation agents and its study in supramolecular chemistry have been used in many areas (Steed & Atwood, 2002; Chen & Jiang, 2011). Cyclodextrins are cyclic oligosaccharides classified according to their number of glucopyranose units. The natural and most employed cyclodextrins are crystalline, homogeneous, non-hygroscopic substances and includes -cyclodextrin (CD, cyclohexaamylose, 6 units of glucopyranose), -cyclodextrin (CD, cycloheptaamilose, 7 units of glucopyranose) and -cyclodextrin (CD, cyclooctaamylose, 8 units of glucopyranose), whose chemical structures are shown in Figure 1 (Szejtli, 1998). They are biocompatible, non-toxic in a wide range of concentration, relatively inexpensive and produced naturally by enzyme degradation of starch (Yorozu et al., 1982).