Isolation, chemical characterization and biological activity of alfalfa (Medicago media Pers.) root saponins

Abstract

Saponins from alfalfa (<em>Medicago media</em> Pers.) roots were isolated and their acid hydrolysis revealed several aglycones that were obtained in crystalline form and characterized. Medicagenic acid, hederagenin and soyasapogenols A. B, C. D, E and F were found. Crude saponins were separated into cholesterol-precipitable and nonprecipitable fractions. The precipitable fraction consisted of medicagenic acid glycosides: glucose, arabinose, xylose and rhamnose were found as their sugar chain components. The nonprecipitable fraction was a mixture of hederagenine and soyasapogenol glycosides, and glucose arthinose. xylose. galactose and glucuronic acid were found in the sugar component,. 7 he medicagenic acid glycosides made up 6% of root dry matter and showed high biological activity. They cuased red blood cells lysis (haemolytic index 3000), completely inhibited <em>Trichoderma viride</em> growth at the concentration of 2.5 Mg. 100 cm<sup>-3</sup> of growth medium and retarded wheat seedling growth at concentrations as low as 100 ppm. The cholesterol-nonprecipitable fraction caused no blood cell lysis and fungus growth inhibition, although it did inhibit seedling growth, but to a much lesser extent than medicagenic acrd glycosides. The detrimental effect of alfalfa root saponins on winter wheat crop after alfalfa is discussed.