Trojanosides I—K: New Cycloartane-Type Glycosides from the Aerial Parts of Astragalus trojanus
Chemical and pharmaceutical bulletin
Astragalus L., the largest genus in the family Leguminosae, is represented by 380 species in the flora of Turkey. 1) The roots of Astragalus species represent a very old and well-known drug in traditional medicine for its usage as an antiperspirant, tonic and diuretic. It has also been used in the treatment of diabetes mellitus, nephritis, leukemia and uterine cancer. 2) In the district of Anatolia, located in South Eastern Turkey, an aqueous extract of the roots of Astragalus is traditionally
... s is traditionally used against leukemia and for its wound-healing properties. Known biologically active constituents of Astragalus roots represent two major classes of chemical compounds, polysaccharides and saponins. 2) Astragalus polysaccharides are known to have anticancer and immune enhancing properties in both in vitro and in vivo experiments.    Chemical studies on Astragalus saponins have reported the presence of cycloartane-type triterpenoid glycosides which were found to exert biological activities (e.g. anti-inflammatory, analgesic, diuretic, hypotensive and sedative effects). 6) Our earlier investigations of Astragalus species resulted in the isolation of a series of cycloartane-type triterpenic saponins. 7-13) We previously reported the isolation and the structure determination of trojanosides A-H from Astragalus trojanus. 10,11) In our continuing search, we have isolated three new cycloartane-type triterpene glycosides, named as trojanosides I-K (1, 2, 5) , from the aerial parts of Astragalus trojanus. Here we report the isolation and the structural elucidation of 1, 2 and 5. The IR spectrum of compound 1 indicated the presence of hydroxyl (3419 cm Ϫ1 ) and ester carbonyl (1726 cm Ϫ1 ) functionalities. The high resolution electrospray ionization mass spectrometry (HR-ESI-MS) spectrum of 1 exhibited an ion peak for [MϩNa] ϩ at m/z 933.3207, which is compatible with the molecular formulae C 47 H 74 O 17 . Taking into account the results of our comprehensive 1 Hand 13 C-NMR studies and previous knowledge derived from metabolites isolated from the genus Astragalus, 7-13) the main features of a cycloartane-type triterpene were evident: characteristic signals due to cyclopropane-methylene protons as an AX system (d 0.23, 0.64, J AX ϭ4.4 Hz, H 2 -19), seven tertiary methyl groups (d 1.Three new cycloartane-type triterpene glycosides have been isolated from the aerial parts of Astragalus trojanus. The structures were established mainly by a combination of one-and two-dimensional NMR techniques [ 1 H-1 H-correlation spectroscopy (COSY), 1 H-13 C-heteronuclear multiple quantum correlation spectroscopy (HMQC), and 1 H-13 C-heteronuclear multiple-bond correlation spectroscopy (HMBC)] and high resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 3-O-b b-(2,3-di-O-acetyl)-D-xylopyranosyl-6-O-b b-D-glucopyranosyl-16-O-acetoxy-20(R),24(S)-epoxycycloartane-3b b,6a a,16b b,25-tetrol, 3-O-[a a-L-rhamnopyranosyl-(1→2)b b-(3,4-di-O-acetyl)-D-xylopyranosyl]-6-O-b b-D-xylopyranosyl-20(R),24(S)-epoxycycloartane-3b b,6a a,16b b,25-tetrol, 3-O-b b-D-xylopyranosyl-6,16-di-O-b b-D-glucopyranosyl-20(R),24(S)-epoxycycloartane-3b b,6a a,16b b,25-tetrol.