Host-guest interaction of trimethoprim drug with cyclodextrins in aqueous solutions: Calorimetric, spectroscopic, volumetric and theoretical approach

Owing to the internal cavity of cyclodextrins, they are very notable to form the inclusion complexeswith various drugs. In present work, the binding of trimethoprim (TMP) drug with native alpha-, beta-, and gamma-cyclodextrins (CDs) were systematically examined using the isothermal titration calorimetry (ITC), spectroscopic {UV-visible, nuclear magnetic resonance (NMR)} methods, dynamic light scattering (DLS) and molecular modeling of the complex formed by host (cyclodextrins) and guest (trimethoprim) molecules. The stability of the TMP-CDs inclusion complexes increases in the following order: alpha-CD <gamma-CD < beta-CD. UV-visible and ITC measurements show similar binding affinity i.e., of the order 10(4) M-1 indicating the better fitting of TMP drug molecules into beta-CD. The NMR (DOSY) experimental results also depicted the maximum change of TMP diffusion rate in the case of complexation of TMP with beta-CD followed by gamma-CD. It is also clear from the molecular docking and DLS studies that beta-CD interact more with the guest molecule. The transfer values (Delta V-t(2)o) are positive increased with the complexity of CDs as: alpha- < beta- < gamma-CDs, indicating that there is greater ability of beta-CD and gamma-CD to interact strongly with trimethoprim as compared to alpha-CD. (C) 2021 Elsevier B.V. All rights reserved.