Re-investigation of the cardenolide glycosides from Gomphocarpus sinaicus

Nine cardenolide glycosides and one aglycone, including five new compounds, were isolated from the aerial parts of the milkweed, Gomphocarpus sinaicus. The elucidation of the structures and stereochemistry of the new glycosides was accomplished using FAB mass spectrometry, H-1 NMR, C-13 NMR, H-1-H-1 COSY, H-1-C-13 COSY, NOE and NOESY. The new compounds were identified as 7,8-dehydrocalotropin, 17 alpha-hydroxy-7,8-dehydrocalotropin, 19-acetylglucocoroglaucigenin, 19-acetylglucofrugoside and humistratagenin. Some of these results differ from those reported in three recent publications on the cardenolides of the same plant species.