Glycosylation Drives Modulation of Triterpenoid Saponin Solubility, Micelle Formation, and Stability

Triterpenoid saponins are amphiphilic plant metabolites with broad agricultural applications. This study compares monodesmosidic α-hederin and hederacolchiside A1 (C3-glycosylated), and bidesmosidic hederacoside C (C3 and C28 glycosylated) to evaluate how glycosylation and pH affect solubility, micelle formation, partitioning, and stability. All three saponins were hydrolytically stable over six months. α-Hederin and hederacolchiside A1 were negligibly soluble in water at pH < 7, whereas hederacoside C maintained a water solubility above 100 µM across pH 2–10. Surface tension measurements in 1% ethanol revealed critical micelle concentrations (CMCs) of 12 µM (α-hederin), 16 µM (hederacolchiside A1), and >500 µM (hederacoside C). Small-angle X-ray scattering (SAXS) showed α-hederin and hederacolchiside A1 formed ellipsoidal micelles (radius ~1.5 nm), while hederacoside C formed spherical micelles above 500 µM (radius ~0.7 nm). Atomic force microscopy (AFM) confirmed monodesmosidic saponins formed needle-like crystalline precipitates in water. Glycosylation governs aggregation behavior and environmental mobility, informing formulation strategies for saponin-based biopesticides and functional food ingredients.