An integral study of cyclodextrins as solubility enhancers of α-methylstilbene, a resveratrol analogue.

trans-α-Methylstilbene (tMS), a resveratrol analogue, has recently been studied in a search for new bioactivities. However, such studies do not take into account that the poor solubility of tMS in aqueous solutions could affect its bioactivity. For this reason, we propose, for the first time, using cyclodextrins (CDs) as solubilizers to increase tMS solubility, in aqueous solutions. The HPLC-RP results obtained, point to a 1 : 1 stoichiometry for all the natural (α-, β- and γ-CD) and modified (HPβCD and MβCD) CDs tested. The KFapp (apparent formation constant) for the tMS-CD complexes was seen to be closely dependent on several factors, including the temperature and type of CD. Indeed, the highest KFapp value was obtained for MβCD, while the KFapp decreased with increasing temperature. In addition, the results showed negative entropy (-8.86 × 10-3 ± 0.40 kJ mol-1 K-1 ) and enthalpy (-16.70 ± 0.98 kJ mol-1 ) changes and a negative Gibbs free energy value at 25 °C (-14.00 ± 0.55 kJ mol-1 ) for the encapsulation process. A computational study carried out using molecular docking calculations showed a high degree of correlation between the computed scores and experimental values. Finally, the complexation of trans-stilbene and pinosylvin with HPβCD was compared with tMS.