The suppression of
imipramine hydrochloride (
IMP)- induced
hemolysis by native
cyclodextrins (alpha-, beta-, and gamma-CDs) and beta-CD derivatives is measured as a function of CD concentration and is quantitatively correlated with the surface tension of the
solution determined at 37.0 degrees C. The modified beta-CDs are more or less adsorbed onto the air-water interface and occupy larger areas than the wider rim of beta-CD. The surface tension data at low CD concentrations in the presence of 3 mM
IMP allow us to estimate the 1:1 binding constants of
IMP with CDs. Both the capabilities of
hemolysis suppression and surface tension elevation for 3 mM
IMP are strong in the order carboxymethyl-beta-CD (
CM) > beta-CD approximately equal to 6-O-glucosyl-beta-CD (G(1)) > gamma-CD > 2-hydroxypropyl-beta-CD (HP) > alpha-CD > or = 2,6-di-O-methyl-beta-CD (DM). The suppression of
IMP-induced
hemolysis is ascribed to the decrease in the concentration of free
IMP molecules. This concentration can be quantitatively estimated from the surface tension data determined at 37 degrees C. Therefore, the suppression of
IMP-induced
hemolysis by most of the CDs can be quantitatively predicted from these surface tension data, regardless of the kind and concentration of CD. However, alpha-CD, HP, and DM are outliers of this prediction. This failure for alpha-CD and HP is ascribed to their weaker competitive binding to
IMP than to membrane
phospholipid. Because DM has a strong hemolytic activity, it does not almost suppress the
IMP-induced
hemolysis.