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

trans-alpha-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 (alpha-, beta- and gamma-CD) and modified (HP beta CD and M beta CD) CDs tested. The K-Fapp (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 M beta CD, while the K-Fapp decreased with increasing temperature. In addition, the results showed negative entropy (-8.86 x 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 degrees 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 HP beta CD was compared with tMS.