Inhibitory effect of 2-hydroxypropyl-beta-cyclodextrin on the foaming generated by the phosphodiester compound of vitamin C and E, EPC-K1

2-Hydroxypropyl-beta-cyclodextrin (HP-beta-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-hydroge n phosphate] potassium salt (EPC-K1). Ultraviolet (UV), circular dichroism (CD) and proton nuclear magnetic resonance (H-1-NMR) spectroscopic studies suggested the formation of inclusion complexes of EPC-K1 with HP-beta-CyD i n aqueous solution. HP-beta-CyD inhibited the foaming generated by EPC-K1 i n aqueous solution in a concentration dependent manner, The inhibitory effe ct of HP-beta-CyD on the foaming was consistent with a restoring effect on the lowered surface tension of aqueous solutions containing EPC-K1. In addi tion, 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-beta- CyD complexes and the surface tension of aqueous solutions containing EPC-K 1 and HP-beta-CyD. Therefore, the inhibitory effect of HP-beta-CyD on the f oaming generated by EPC-K1 could be attributable to the abatement in the su rface activity of EPC-K1 by inclusion complexation with MP-beta-CyD. These data suggest that HP-beta-CyD is useful in topical liquid preparations such as lotions of EPC-K1 used in pharmaceutics and cosmetics.