Preparation and physicochemical characterization of inclusion complex of pterostilbene-hydroxypropyl--cyclodextrin for enhancing the application of pterostilbene in cosmetics

Pterostilbene (PTS) is a kind of natural plant polyphenol with a high antioxidant capacity. However, it is a challenge to apply PTS in cosmetic formulations due to its lower water solubility and stability. In order to overcome these limitations, a PTS-hydroxypropyl-beta-cyclodextrin (PTS-HP-beta-CD) inclusion complex with a 1:1 host-guest molar ratio was prepared using the stirred solution method. The inclusion complex of PTS-HP-beta-CD was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), proton nuclear magnetic resonance (H-1 NMR), two-dimensional rotating frame nuclear Overhauser effect spectroscopy (2D ROESY), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). Additionally, the photostability and antioxidant activity of PTS and PTS-HP-beta-CD were also evaluated. After complexation with HP-beta-CD, the water solubility of PTS was found to be 81-fold higher by phase solubility. The results of XRD, SEM, H-1 NMR, and 2D ROESY demonstrated that PTS was successfully encapsulated by HP-beta-CD and formed a 1:1 inclusion complex. After the formation of the PTS-HP-beta-CD inclusion complex, TG, DSC, UV irradiation, DPPH radical scavenging activity, hydroxyl radical scavenging activity, and superoxide anion radical scavenging activity revealed that the stability and antioxidant activity of PTS were enhanced. Therefore, this work could provide a promising approach to improve the application of PTS or other polyphenolic substances in cosmetic formulations.