The inclusion complexes between daidzein and three cyclodextrins (CDs), namely β-cyclodextrin (β-CD), methyl-β-cyclodextrin (Me-β-CD, DS = 12.5) and (2-hydroxy)propyl-β-cyclodextrin (HP-β-CD, DS = 4.2) were prepared. The effects of the inclusion behavior of daidzein with three kinds of cyclodextrins were investigated in both solution and solid state by methods of phase-solubility, XRD, DSC, SEM, ¹H-NMR and 2D ROESY methods. Furthermore, the antioxidant activities of daidzein and daidzein-CDs inclusion complexes were determined by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) method. The results showed that daidzein formed a 1:1 stoichiometric inclusion complex with β-CD, Me-β-CD and HP-β-CD. The results also showed that the solubility of daidzein was improved after encapsulating by CDs. ¹H-NMR and 2D ROESY analyses show that the B ring of daidzein was the part of the molecule that was most likely inserted into the cavity of CDs, thus forming an inclusion complex. Antioxidant activity studies showed that the antioxidant performance of the inclusion complexes was enhanced in comparison to the native daidzein. It could be a potentially promising way to develop a new formulation of daidzein for herbal medicine or healthcare products.

The swelling behavior of gelatin films with different extraction processes are investigated. The results showed that the swelling ratio of the gelatin film extracted by alkaline hydrolysis of collagen (type-B) in a range of pH environments was higher than the one extracted by enzymatic hydrolysis collagen (type-E). In the drug releasing simulation, type-B gelatin capsules also showed a faster collapse rate than type-E gelatin capsules. Based on analyzing relative molecular weight distribution of type-B and type-E gelatins, the more widely distributed relative molecular weight is the key attribution for enabling easier diffusion of water molecules inside the porous channels of peptide chains. Furthermore, with the pH of solution environment far from the isoelectric point (pI) of gelatin films, the swelling ratios were found to increase remarkably, which is due to electrostatic repulsion expanding the pore size of peptide chains. Finally, the addition of SO₄²⁻ in gelatin film was performed to confirm the dominant effect of component compared to pI on swelling behavior of gelatin films.

In recent years, phloretin has gained wide interest because of its antioxidant, antitumor, and skin whitening properties. However, its low water solubility and low stability make its usage in clinical application difficult, especially in water-based formulations. Phloretin–methyl-β-cyclodextrin (phloretin–Me-β-CD) and phloretin–(2-hydroxy)propyl-β-cyclodextrin (phloretin–HP-β-CD) inclusion complexes were prepared by the freeze-drying method. Phase solubility studies indicated that the ratio of the host–guest molecules was 1 : 1. The inclusion behavior has been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), proton nuclear magnetic resonance (¹H NMR), and two-dimensional rotational frame nuclear Overhauser effect spectroscopy (2D ROESY). The results showed that the water solubility of phloretin improved after encapsulation. The reducing power (RP) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity tests revealed that the antioxidant activity of phloretin improved after the formation of inclusion complexes with Me-β-CD and HP-β-CD. This could be a promising way to improve phloretin as a water-based formulation of antioxidants.