Abstract: The inclusion complexation behavior of phloretin with methyl-β-cyclodextrin (Me-β-CD) and (2-hydroxy) propyl-β-cyclodextrin (HP-β-CD) was investigated quantitatively by the phase solubility method. Water-soluble inclusion complexes of phloretin and two β-CD derivatives were prepared by the freeze-drying method and structurally characterized by infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, the antioxidant activities of phloretin and the inclusion complexes were determined by reducing power (RP) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging methods. The tyrosinase inhibitory activities of phloretin and the inclusion complexes were also investigated. The results proved that phloretin formed 1:1 stoichiometric inclusion complex with Me-β-CD and HP-β-CD, respectively. The water solubility and antioxidant activity of phloretin were greatly enhanced in the presence of CDs, providing a good way to develop water-based health food formulations. Additionally, phloretin and its inclusion complexes were observed to efficiently inhibit tyrosinase activity. The inclusion complexes could be developed as a natural, efficient and environmental friendly food preservative.

Key words: phloretin, β-cyclodextrin derivatives, inclusion complex, solubility, tyrosinase inhibitory activity, antioxidant activities