Molecular Complexation of Hederasaponin C with Cholesterol in Aqueous Isopropyl Alcohol

The 1:1 molecular complex of ivy triterpene glycoside hederasaponin C (HedC) with cholesterol (Chol) was obtained in aqueous isopropyl alcohol. The stability constant of (3.3 ± 0.7)∙106 (mol/L)–1 was calculated for the complex. The complexation was studied by UV- and ATR IR-Fourier spectroscopy, and method of isomolar series. The hydrogen bonds and hydrophobic interactions are formed in the molecular complex.

MOLECULAR COMPLEXES OF IVY TRITERPENE GLYCOSIDES WITH CHOLESTEROL

Molecular complexes of cholesterol with dominant triterpene saponins from members of the ivy genus Hedera L. (Araliaceae Juss.) – monodesmosidic glycoside α-hederin (hederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranoside) and bisdesmosidic glycoside hederasaponin C (hederagenin 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranosyl-28-О-α-L-rhamnopyranosyl-(1→4)-О-β-D-glucopyranosyl-(1→6)-О-β-D-glucopyranoside) as well as with minor monodesmosidic glycoside hederoside F (hederagenin 3-О-β-D-glucopyranosyl-(1→2)-О-β-D-glucopyranoside) have been prepared. The complexation has been investigated by methods of isomolar series in the spectrophotometric version and FT-IR spectroscopy with a universal optical attenuated total reflection (ATR) accessory. It was shown that a-hederin, hederasaponin C and hederoside F form a 1 : 1 complexes with cholesterol, having a stability constants (5.6±0.1)×104, (4.7±0.1)×104 and (6.0±0.6)×104 M–1 respectively (in 70% aqueous ethanol et 25 °С). The constants are calculated on the basis of isomolar curves. The complexes of cholesterol with ivy monodesmosidic glycosides are more stable. Intermolecular interaction in the complexes is carried out by hydrogen bonds formation of type –С=О···Н–О– (for monodesmosidic glycosides) and –(Н)О···Н–О– (for bisdesmosidic glycoside). Hydrophobic contacts of the aglycone part of glycosides (hederagenin) with a lipophilic cholesterol molecule are possible. As a result, changes in some frequencies of the absorption bands of CH bonds are observed, which was established by IR spectroscopy.