Cycloascauloside a from Astragalus caucasicus leaves

Abstract

In continuation of research on isoprenoids from plants of the genus Astragalus [1], we isolated from leaves of A. caucasicus Pall. (Leguminosae L.) compounds called cycloascaulosides A, B, and C. Herein the structure of cycloascauloside A is reported.The PMR spectrum of cycloascauloside A (1) contained two 1H doublets coupled in an AB-type system at 0.39-0.54 ppm with SSCC 2 J = 4.5 Hz in addition to signals for seven methyls at 0.80-1.78 ppm. This enabled 1 to be considered as a cycloartane triterpenoid [1][2][3]. This conclusion was confirmed by absorption bands in the IR spectrum at 3045 and 1452 cm -1 and the preparation of cyclogalegigenin (2) upon acid hydrolysis of 1 and its Smith decomposition [2][3][4]. The carbohydrate part of the hydrolysate contained D-glucose and L-rhamnose in a 1:1 ratio according to paper (PC) and gas chromatography [5]. 1: R = α-L-Rhap-(1→6)-β-D-(2-O-Ac)-Glcp 2: R = H 3: R = α-L-Rhap-(1→6)-β-D-Glcp 4: R = β-D-GlcpThe IR spectrum of 1 exhibited absorption bands at 1755 and 1240 cm -1 (ester); the PMR spectrum, a 3H singlet at 1.98 ppm belonging to an acetyl. As expected, the 13 C NMR spectrum of 1 contained signals for C atoms of one acetyl at 19.70 and 170.02 ppm.Glycoside 1 treated with dilute base solutions gave progenin 3, which underwent partial hydrolysis. The resulting products included cyclogalegigenin and glycoside 4, acid hydrolysis of which gave D-glucose and genin 2. Therefore, D-glucose was directly bound to cyclogalegigenin.

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.…”

Chemical constituents of the aerial part of Astragalus bungeanus

“…The genin dissolved in acetone in the presence of H 2 SO 4 and formed an acetonide, mp 222-225°C, indicating the presence of an D-diol in the side chain and, therefore, identifying it as cyclocanthogenin [6]. D-Glucose and D-xylose in a 1:1 ratio were found by PC and HPLC analysis of the carbohydrate part of the hydrolysate [9,10].…”