title: Stability of saponins in alcoholic solutions: ester formation as artifacts.
abstract: Saponins containing a free carboxylic group in the molecule give the corresponding esters as artifacts when stored for a long time in alcoholic solutions. Two saponins from Medicago sativa L., chosen on the basis of their different positions of the carboxylic group in the molecule, were refluxed with methanol and ethanol under neutral conditions. 3,28-di-O-glu medicagenic acid possesses a carboxylic group on the triterpenic moiety, whereas soyasaponin I, a glycoside of soyasapogenol B, has a glucuronic acid unit as the first sugar linked to the triterpene structure. Artifacts were quantified by HPLC. The peaks identified as the corresponding esters were examined during boiling from 1 h to 5 days. Quantitative results indicated that the carboxylic group on the sugar moiety, as for soyasaponin I, is more reactive than that on the triterpenic structure, as for 3,28-di-O-glu medicagenic acid. Saponins having the free carboxylic groups create enough acidity in their alcoholic solutions to catalyze the formation of the corresponding esters.
authors.affiliation: Istituto Sperimentale per le Colture Foraggere, viale Piacenza 29, 26900 Lodi, Italy. aldotava@katamail.com
authors.forename: Aldo
authors.initials: A
authors.lastname: Tava
authors.forename: Mariella
authors.initials: M
authors.lastname: Mella
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Bialy
authors.forename: Marian
authors.initials: M
authors.lastname: Jurzysta
mesh_terms: D016477:Artifacts; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004355:Drug Stability; D000431:Ethanol; D009682:Magnetic Resonance Spectroscopy; D000455:Medicago sativa / Q000737:chemistry*; D000432:Methanol; D012503:Saponins / Q000737:chemistry*; D012996:Solutions
chemical_list: D012503:Saponins; D012996:Solutions; D000431:Ethanol; D000432:Methanol