Analysis of the thermal fluctuations in inclusion complexes of genistein with β-cyclodextrin derivatives.

Graphical abstract Highlights • EINS is applied to study molecular mobility of Gen/β-CDs inclusion complexes. • At ∼100 K a first anharmonic contribution, due to CH 3 rotations, is observed. • At higher T a second anharmonic process occurs, due to H-bond network relaxation. • The hindered mobility of inclusion complexes is due to "host-guest" interactions. • Dynamics was connected to stability, indicating HP-β-CD as the best carrier. Abstract Elastic incoherent neutron scattering was employed to investigate the molecular mobility of inclusion complexes, formed by two β-cyclodextrin (β-CD) derivatives, namely (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) and methyl-β-cyclodextrin (Me-β-CD), with Genistein (Gen), a phytoestrogen having antioxidant and anticarcinogenic activities, compared to the physical mixtures and single components. The results, collected in the 20–300 K temperature range, revealed a purely vibrational dynamics up to ∼100 K, where a first anharmonic contribution, corresponding to the methyl rotational dynamics, was observed and represented by an Arrhenius trend. At higher temperatures, a second anharmonic process, also found to obey an Arrhenius-like behavior, occurred at T d and was mainly ascribed to the relaxation of the H-bond network formed by host and guest molecules. Enthalpy and entropy changes associated to the activated anharmonic processes were obtained. The picoseconds timescale dynamics was finally connected to the thermal stability, suggesting HP-β-CD as the most effective carrier for Gen. [ABSTRACT FROM AUTHOR]