Arundic acid, (R)-(-)-2-propyloctanonic acid, is a novel neurological agent for intractable neurodegenerative diseases. However, arundic acid, an oily drug, has low aqueous solubility and severe bitter/irritating tastes. Consequently, these physicochemical properties of arundic acid need to be improved to develop its pharmaceutical preparations. In the present study, we evaluated whether parent cyclodextrins (CyDs) and 2-hydroxypropylated CyDs (HP-CyDs) can interact with arundic acid, and have powderization, solubilization and taste-masking properties. Of various CyDs, HP-β-CyD had the most potent solubilizing effect for arundic acid. UV and (1)H NMR spectroscopic studies demonstrated that arundic acid formed inclusion complexes with CyDs at a molar ratio of 1:1 in solution. The complexation with CyDs changed an oily form of arundic acid to a solid form. The gustatory sensation studies indicate that of various CyDs, HP-β-CyD and γ-CyD showed the most significant taste-masking effects in solution and powders, respectively. HP-β-CyD significantly reduced the response of the electric potential caused by the adsorption of arundic acid to the taste sensor. These results suggest that hydrophilic CyDs have potential as multifunctional excipients for preparing solutions and powders containing arundic acid.
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