Three Astragalus saponins I, II, III have been isolated from roots of A. membranaceus Bunge (Leguminosae). Astragalus saponin I is the major constitutent. The structure of astramembangenin C30H50O5 obtained from saponin I by Smith's oxidative degradation with NaIO4 followed by NaBH4 reduction, was assigned as 1 by means of spectroscopic analysis (IR, ^1H NMR, ^1^3C NMR and MSe as well as chemical degradation. The configuration of C20 and C24 of 1 was established as S and R respectively by means of^1H NMR spectroscopy using lanthanide shift reagent.

Key words: INSTRUMENTAL ANALYSIS, CHEMICAL COMPOSITION, ASTRAGALUS, ASTRAGALUS MEMBRANACEUS BUNGE