Investigation of water-soluble inclusion complex of hypericin with β-cyclodextrin polymer

A water-soluble inclusion complex of hypericin (HY) with β-cyclodextrin polymer (CDP) was achieved by supramolecular interactions between HY and CDP. The inclusion complex (HY-CDP) was characterized by 1H NMR, FTIR, and UV–vis spectroscopies. Compared with HY, the water-solubility of HY-CDP was greatly enhanced because of the water-soluble CDP host. The mole ratio of β-cyclodextrin (β-CD) unit in CDP to HY was determined as 2:1. At 25 °C, the dissociated constant of HY-CDP was measured as 1.47 × 10−7 mol L−1 by UV–vis spectroscopy. In the formation of inclusion complexes, CDP could overcome the β-CD drawbacks – such as the poor water-solubility and the restriction of single cavity size, indicating it was able to use as a universal solubilizer for pharmaceutical application.