Characterization of Mammea A/AA in solution and in interaction with β-cyclodextrin: UV–visible spectroscopy, cyclic voltammetry and DFT-TDDFT/MD study

Abstract

Mammea A/AA (MA) was recently introduced as a new anticancer, antioxidant and antimicrobial compound, but presenting some cellular toxicity. In this work, MA in solution and interacting with β-cyclodextrin (β-CD) was characterized by UV–visible absorption spectroscopy, cyclic voltammetry and theoretical density functional theory (DFT), time dependent density functional theory (TDDFT) calculations and molecular dynamic (MD) simulation. We found that the absorbance of this compound was governed by the relative wavelength position of its charge transfer (CT) and locally excited (LE) states, which are respectively sensitive to polarity and H-bonding. Comparison of the spectroscopy of MA in solution and in presence of increasing amount of β-CD was showing a systematic blue shift and hyperchromic effect, while a decrease of the voltammetry signal peak was observed, which we attributed to the formation of an inclusion complex with β-CD. A binding constant of 7.2×104M−1 was estimated and the stoichiometry of the complex was found to be 1:1. Theoretical calculations have shown that this complex does not affect the antioxidant potency of MA and that the structure of β-CD complex is stabilized by two H-bonds between MA carbonyl groups and the β-CD wider rim hydroxyl groups, as well as attractive Van der Waals forces. These results suggest that the binding of MA to β-CD is strong enough and hence allowing this compound to be stored and carried by β-CD for in vivo loading.