A 5,7-Dimethoxyflavone/Hydroxypropyl-β-Cyclodextrin Inclusion Complex with Anti-Butyrylcholinesterase Activity
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This study aimed to improve the water solubility of 5,7-dimethoxyflavone (5,7-DMF) isolated from Kaempferia parviflora by complexation with 2-hydroxypropyl-β-cyclodextrin (HPβ-CD). The phase solubility profile of 5,7-DMF in the presence of HPβ-CD was classified as AL-type and indicated a 1:1 mole ratio. Differential scanning colorimetry, X-ray diffraction, NMR and SEM analyses supported the formation of a 5,7-DMF/HPβ-CD inclusion complex involving the A ring of 5,7-DMF inside the HPβ-CD cavity. This is the first example of CD inclusion with the A ring of non-hydroxyl flavones. The stability and binding constants of the complexes were determined using the phase solubility and UV-vis absorption spectroscopy, respectively. The water solubility of 5,7-DMF was increased 361.8-fold by complexation with HPβ-CD and overcame the precipitation problem observed in aqueous buffers, such as during in vitro anti-butyrylcholinesterase activity assays. The 1:1 mole ratio of the 5,7-DMF/HPβ-CD complex showed a 2.7-fold higher butyrylcholinesterase inhibitory activity (in terms of the IC50 value) compared to the non-complexed compound.
KEY WORDS5,7-dimethoxyflavone butyrylcholinesterase inhibitory activity hydroxypropyl-β-cyclodextrin inclusion complex water solubility
This work was financially supported by the Higher Education Research Promotion and National Research University Project of Thailand, the Office of the Higher Education Commission (FW645A), National Research University project of CHE(AM1077I), the Special Task Force for Activating Research (STAR) from the Centenary Academic Development Project, Chulalongkorn University, and the Program of Center of Excellence Network from Nanotechnology Center (NANOTEC), NSTDA, Ministry of Science and Technology, Thailand. The authors are also grateful for English corrections by Robert Butcher of the Publication Counseling Unit, Faculty of Science, Chulalongkorn University.
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