Inclusion complex of astaxanthin with hydroxypropyl-β-cyclodextrin: UV, FTIR, 1H NMR and molecular modeling studies

The structure and complex mode of the inclusion complex of astaxanthin with hydroxypropyl-β-cyclodextrin (HPCD) were investigated by UV, FTIR, 1H NMR and molecular modeling test. UV, FTIR and 1H NMR results indicated that the hexatomic ring of the astaxanthin molecules were partly included into the HPCD cavities. The implementation of molecular modeling test confirmed that the complexation could reduce the energy of the system and the complex of 2:1 host–guest stoichiometry had the lowest ΔE value, −30.57 kcal/mol, two hexatomic ring ends of one astaxanthin molecule inserted into two HPCD cavities respectively, and that should be the most predominant configuration.