Calysepins I–VII, Hexasaccharide Resin Glycosides from Calystegia sepium and Their Cytotoxic Evaluation

Seven new hexasaccharide resin glycosides, named calysepins I–VII (1–7), with 27-membered rings, were obtained from the aerial parts of Calystegia sepium. Their structures with absolute configuration were established on the basis of spectroscopic data interpretation analysis and the use of chemical methods. They were defined as hexasaccharides composed of one d-quinovose, four d-glucose, and one l-rhamnose unit, and their sugar moieties were partially acylated by (2S)-methylbutanoic acid in 1–7 and (2R,3R)-nilic acid in 1–5 and 7, which mainly differed at the positions of acylation. Additionally, calysepin IV (4) exhibited cytotoxicity against A549 cells with an IC50 value of 5.2 μM.