Saurobacciosides A - C: three new glycosides from Sauropus bacciformis with their cytotoxic activity

Three new glycosides, named as saurobaccioside A (1), saurobaccioside B (2), saurobaccioside C (3), together with five known magastigmanes, canangaionoside (4), (6S,9S)-roseoside (5), cucumegastigmane I (6), icariside B5 (7), linarionoside A (8) were isolated from the whole plant of Sauropus bacciformis (L.) Airy Shaw. Their structures were established by extensive spectroscopic analysis (UV, IR, HR-ESI-MS and NMR) and by comparison of the spectral data with those reported in the literature. The absolute configurations of compounds 2 and 3 were elucidated by experimental CD spectra. Compounds 1-8 were screened their cytotoxic activities towards CAL27 and MDAMB231 cancer cell lines. Compound 1 exhibited significant cytotoxic activity towards CAL27 and MDAMB231 cell lines with IC₅₀ values of 3.21 ± 0.23 and 4.75 ± 0.17 µM, respectively, which were smaller than those of positive control capecitabine (IC₅₀: 8.20 ± 0.75 and 5.20 ± 0.89 µM). Other compounds (2-8) were inactive.