Study of micelles and surface properties of triterpene saponins with improved isolation method from Hedera helix

Abstract

Triterpene saponin fractions were extracted from Hedera helix, and in-depth analysis of their physicochemical properties was conducted. Hederasaponin B and hederacoside C were extracted from Hedera helix leaves, and their purification was carried out using reverse phase column chromatography with a modified method, providing an affordable alternative to HPLC. Structurally, hederacoside C differs from hederasaponin B only by the presence of a hydroxyl group at the carbon 23 of the aglycon. The critical micelle concentration (cmc) measurement confirmed hydrophilic nature of hederacoside C that led to a higher cmc value compared to hederasaponin B and alpha-hederin. Therefore, the cmc value of hederasaponin B is nearly an order of magnitude lower compared to hederacoside C. Additionally, the study of the surface tension revealed that the more lipophilic alpha-hederin displayed a greater surface tension value (γcmc = 39.8 mN·m−1) compared to hederasaponin B and hederacoside C. Measurements of the surface tension dependence on the concentration in water were enabled to determine the area corresponding to a single saponin molecule at the water/air phase interface (Acmc). Notably, structural changes had negligible effects, as Acmc values remained practically identical. Particle size determination further indicated that hederacoside C forms only micelles compared to the remaining substances that showed signs of vesicles formation. Alpha-hederin, as the only measured molecule capable of ionization, showed a negative zeta potential.