Abstract
2-Hydroxypropyl-β-cyclodextrin (HP-β-CyD) was examined for potential use as an inhibitor of foaming generated by L-ascorbic acid 2-[3, 4-dihydro-2, 5, 7, 8-tetramethyl-2-(4, 8, 12-trimethyl-tridecyl)-2H-1-benzopyran-6-yl-hydrogen phosphatel potassium salt (EPC-K1). Ultraviolet (UV), circular dichroism (CD) and proton nuclear magnetic resonance (1H-NMR) spectroscopic studies suggested the formation of inclusion complexes of EPC-K1 with HP-β-CyD in aqueous solution. HP-β-CyD inhibited the foaming generated by EPC-K1 in aqueous solution in a concentration dependent manner. The inhibitory effect of HP-β-CyD on the foaming was consistent with a restoring effect on the lowered surface tension of aqueous solutions containing EPC-K1. In addition, there is a negative correlation between the free EPC-K1 concentration calculated from the stability constants of the 1 : 1 and 1 : 2 EPC-K1/HP-β-CyD complexes and the surface tension of aqueous solutions containing EPC-K1 and HP-β-CyD. Therefore, the inhibitory effect of HP-β-CyD on the foaming generated by EPC-K1 could be attributable to the abatement in the surface activity of EPC-K1 by inclusion complexation with HP-β-CyD. These data suggest that HP-β-CyD is useful in topical liquid preparations such as lotions of EPC-K1 used in pharmaceutics and cosmetics.
