Triterpene glycosides from Astragalus and their genins. LXXX. Cyclomacroside D, a new bisdesmoside

Abstract

In continuation of research on cycloartane triterpenoids from plants of the genus Astragalus (Leguminosae) [1], we determined the structure of the new compound H [2], which was isolated from Astragalus macropus Bunge and which we called cyclomacroside D (1).PMR and 13 C NMR spectra of 1 (Table 1) indicated the presence of a 1,1,2,2-tetrasubstituted 9,19-three-membered ring (1H doublets for an AX system at δ 0.44 and 0.89 with SSCC 2 J = 4 Hz, C-9 and C-10 singlets, and C-19 triplet). This classified the studied glycoside as a triterpenoid of the cycloartane series [3][4][5][6].Comparison of the 13 C NMR spectra of 1 and the genin 3 showed that cyclomacroside D was a derivative of cyclomacrogenin B.Acid hydrolysis of cyclomacroside D and subsequent analysis of the carbohydrate part of the hydrolysate by paper chromatography detected D-xylose and L-rhamnose. The PMR and 13 C NMR spectra of 1 contained two sets of resonances for monosaccharide units. Therefore, 1 was a bioside containing D-xylose and L-rhamose in a 1:1 ratio.As expected, the native genin cyclomacrogenin B could not be detected in the genin part of the acid hydrolysate of the glycoside. The presence of the 1α-hydroxyl, which is easily eliminated in acidic medium, caused migration of the 9,19-bond to a 1,19-bond and generated a 9(11) double bond [3].Enzymatic hydrolysis of cyclomacroside D by gastric juice of the grapevine snail (Helix pomatia) formed progenin 2, which was identified as cyclomacroside C [1]. This indicated that the L-rhamnose was bonded to the genin at C-3 of the α-glycoside bond and that the monosaccharide has the 1 C 4 -conformation. In agreement with this, the HMBC spectrum contained a cross-peak between resonances for the anomeric H atom of the α-L-rhamnose unit and C-3 of the genin. The resonance for H-1 of D-xylose in the same HMBC spectrum correlated with the resonance of C-24, indicating the site of attachment of the pentose.In fact, C-3 and C-24 experienced a glycosylation effect and resonated at δ 84.19 and 89.56. Chemical shifts of H and C atoms and SSCC of D-xylose in the PMR and 13 C NMR spectra of 1 indicated the pyranose form, the 4 C 1 -conformation, and the β-configuration of the studied monosaccharide.Thus, cyclomacroside D has the structure 24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-L-rhamnopyranoside-24-O-β-D-xylopyranoside.

Triterpene glycosides from Astragalus and their genins. LXXXII. Cyclomacroside B, a new glycoside

“…Therefore, cyclomacroside B was an ester. As expected, 1 was hydrolyzed by base to form cyclomacroside D (2) [6], the formation of which from new glycoside 1 confirmed the conclusion about the location, size of the oxide ring, and conformation and configuration of the monosaccharide units.…”

Compounds from the pods of Astragalus armatus with antioxidant, anticholinesterase, antibacterial and phagocytic activities

“…Phytochemical studies of both extracts afforded seven compounds (1-7) including flavonoids (1-5), one cyclitol (6) and one saponin (7) (Figure 1). The compounds were elucidated as isorhamnetin (1) (Lee et al 2008 (Yasukawa & Takido 1987), and kaempferol- (Leite et al 2001), pinitol (6) (Pistelli et al 1998), and 24R-cycloartan-1a, 3b, 7b, 24, 25-pentaol- (Iskenderov et al 2009) using the 1D-, and 2D-NMR, and MS techniques.…”

Five New Triterpene Bisglycosides with Acyclic Side Chains from the Rhizomes of Cimicifuga foetida L.

“…Additionally, two anomeric protons at d C-NMR data of C-24 were comparable to analogue compounds having a 24R configuration. [5][6][7] Consequently, the structure of 1 was elucidated as lanosta-9(11)-en-3b,16b,24R,25…”