Cyclogaleginoside D from Astragalus galegiformis stems

Abstract

Astragalus galagiformis stems. The structure of the glycoside was established using chemical transformations and IR, PMR, and 13 C NMR spectral data.We have previously isolated from A. galegiformis L. stems and identified cycloartane glycosides cyclogaleginosides A, B, and E [2, 3]. In continuation of chemical research on isoprenoids from plants of the genus Astragalus (Leguminosae) [1], we isolated in addition to the aforementioned glycosides another two polar glycosides C and D. Herein the structure of cyclogaleginoside D (1) is examined.The PMR spectrum of 1 contained a 1H doublet for an AX system at 0.38 and 0.54 ppm with SSCC 2 J = 4.5 Hz in addition to signals for seven methyls in the range 0.91-1.41 ppm. This indicated that the compound was a triterpenoid cycloartane [1]. This was consistent with the isolation of cyclogalegigenin (3) as the genin from the acid-hydrolysis products of cyclogaleginoside D. Paper chromatography detected D-xylose and D-glucose in the carbohydrate part of the acid-hydrolysis products. The PMR and 13 C NMR spectra of 1 (Table 1) contained signals for two carbohydrate units and indicated that the studied glycoside was a bioside.A 3H singlet at 2.10 ppm in the PMR spectrum of 1 was consistent with one acetic acid moiety. As expected, the 13 C NMR spectrum of 1 contained signals for C atoms of one acetyl at 21.1 and 169.5 ppm.Alkaline hydrolysis of 1 gave glycoside 2, which was identified as cyclogaleginoside E [3]. Therefore, cyclogaleginoside D is cyclogaleginoside E monoacetate.The attachment site of the acetyl was found by comparing the 13 C NMR spectra of 1 and 2. Atoms C-6 and C-16 of 1 resonated in the 13 C NMR spectrum of 1 at 69.07 and 74.40 ppm, respectively. These values were practically the same as those in the 13 C NMR spectrum of 2. This means that the acetyl is not located on the genin of 1.

A Review of Recent Research Progress on the Astragalus Genus

“…As the summarized results shown in Table 1, Table 2 and Table 3 and Figure 1, Figure 2, Figure 3 and Figure 4, 46 kinds of Astragalus species have been studied for their chemical constituents in recent years [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,…”

“…So the 20,24-epoxycycloartane-type saponins like 64 – 107 are derived from secondary metabolic pathways. Also there are usually 20 R , 24 S ( 64 – 10 1 ) [6,10,12,13,22,26,27,28,39,42,43,44,45,46,47,48,49,50,51,52,53] or 20 S ,24 R ( 102 – 107 ) [54,55,56,57] steric configurations.…”

Triterpenoids

“…98,99 Other new glycosides include two acetylcimifugosides 166 and 167 from Cimifuga racemosa 100 and cycloartane-3b,7b,24R,25,29-pentol 24-glucoside 168. 101 Other cycloartane glycosides with known genins have been reported from Camptosorus sibiricus, 102 Thalictrum fortunei, 103 Astragalus baibutensis (baibutoside), 104 Astragalus galegiformis (cyclogaleginoside D), 105 Astragalus caucasicus leaves (cycloascauloside A), 106 Cimicifuga foetida 107 and Cimifuga racemosa (cimiracemoside), 108,109 Astragalus oleifolius (oleifoliosides A and B) 110 and Souliea vaginata (soulieosides D and E). 111 The structures and stereochemistry of cycloorbicoside D 169 from Astragalus orbiculatus, 112,113 130 and parvimosides A and B from Stichopus parvimensis.…”