Modeling of the inclusive complexation of natural drug trans 3,5,3′,4′-tetrahydroxystilbene with β-cyclodextrin

In this study, the complexation of trans 3,5,3′,4′-tetrahydroxystilbene, also known as piceatannol (PIC), with β-cyclodextrin (β-CD) was investigated using the semi-empirical PM3 method in vacuum. Two orientations were assessed for the encapsulation of piceatannol in the cavity of β-cyclodextrin. The orientation in which the A aromatic ring of PIC was directed toward the inner cavity of β-CD was named 'A' and that in which the B aromatic ring is located inside the β-CD cavity was named 'B'. The results indicated that both orientations were favorable for the complexation of PIC/β-CD. Indeed, the energy difference between the two orientations was less than 1 kcal/mol. Additionally, the negative interaction energies obtained for a 1:1 stoichiometry suggest that the complexation process is exothermic and indicate that the PIC/β-CD complex was highly stable and enthalpically driven. HOMO and LUMO investigations confirmed these results.