Cardiac Glycosides from Erysimum cheiranthoides
Chemical and pharmaceutical bulletin
Erysimum cheiranthoides L. (Cruciferae) is a Chinese crude drug used for treating cardiac diseases, weak cardiopalmus, edema, dyspepsia, etc. 1) In previous papers, 2-4) we reported seven new cardenolides. As a continuing study on the constituents in the seeds, three additional new glycosides named cheiranthosides VIII, IX and X were isolated, and their chemical structures are described here. Cheiranthoside VIII (1) , obtained as a white powder, [a] D Ϫ5.2°(MeOH), showed a quasimolecular ion at
... m/z 711 [MϪH] Ϫ in the negative FAB-MS. Its 1 H-NMR spectrum displayed signals due to H 3 -18 (3H, s) at d 1.00, H-17 (1H, br d, Jϭ8.5 Hz) at d 2.78, H 2 -21 (each 1H, br d, Jϭ18.3 Hz) at d 4.98 and 5.28, H-22 (1H, s) at d 6.12, CHO-19 at d 10.37 on the cardiac steroidal framework, and two anomeric protons at d 4.57 (1H, d, Jϭ7.3 Hz) and 5.38 (1H, d, Jϭ8.5 Hz) , and H 3 -6 at d 1.52 (3H, d, Jϭ6.1 Hz) representing of one 6-deoxysugar in the sugar moiety. The 13 C-NMR spectrum showed signals due to a total of 35 carbons, among which 23 carbon signals were originated from the steroidal aglycone part and were coincident with those of strophanthidin; the remaining 12 carbons should be assigned to a sugar moiety. Comparative studies of the 1 H-and 13 C-NMR spectra with those of the glycosidic linkages of cheiranthosides already obtained from the seeds of the title plant resulted in the identification of 1 with that of the sugar linkage, b-D-glucopyranosyl-(1→4)-b-D-antiaropyranosyl 5-7) moiety, of cheiranthoside VII. 4) Heteronuclear multiplebonds correlation (HMBC) spectrum of 1 showed the connectivities between C-3 (d C 74.8) of the aglycone and the H-1 (d H 5.38) of antiarose, and between the H-1 (d H 4.57) of glucose and the C-4 (d C 79.1) of antiarose. Therefore, 1 was characterized as 3-O-b-D-glucopyranosyl-(1→4)-b-D-antiaropyranosyl strophanthidin, as shown in the Formulae. Cheiranthoside IX (2), obtained as a white powder, [a] D ϩ1.8°(MeOH), showed a quasimolecular ion peak at m/z 711 [MϪH] Ϫ in the negative FAB-MS. The 1 H-NMR spectrum showed signals due to H 3 -18 (3H, s) at d 1.03, H-17 (1H, br s) at d 2.80, H 2 -21 (each 1H, br d, Jϭ18.3 Hz) at d 5.05 and 5.33 , H-22 (1H, s) at d 6.12 in the aglycone part, and two anomeric protons at d 4.92 (1H, d, Jϭ7.3 Hz) and 5.46 (1H, br d, Jϭ9.8 Hz) and a methyl group at d 1.54 (3H, d, Jϭ6.7 Hz) of a 6-deoxyhexosyl moiety in the sugar part. The 13 C-NMR spectrum of 2 showed a total of 35 carbon signals, among which 23 were assigned to an aglycone, in Three new cardiac glycosides named cheiranthoside VIII (1), cheiranthoside IX (2) and cheiranthoside X (3) were isolated from the seeds of Erysimum cheiranthoides. Based on spectroscopic data, the structures of 1-3 were characterized as strophanthidin 3-O-b b-D-glucopyranosyl-(1→4)-b b-D-antiaropyranoside, cheiranthidin 3-Ob b-D-glucopyranosyl-(1→4)-b b-D-boiviopyranoside and cheiranthidin 3-O-a a-L-rhamnopyranosyl-(1→4)-b b-D-digitoxopyranoside, respectively. The aglycone moiety possessing a carboxyl group at C-10 of 2 and 3 was regarded to be determined for the first time.