Tricalysionoside A, a Megastigmane Gentiobioside, Sulfatricalysines A-F, and Tricalysiosides X-Z, ent-Kaurane Glucosides, from the Leaves of Tricalysia dubia
Further isolation work on the water-soluble fraction of a MeOH extract of Tricalysia dubia afforded one new megastigmane gentiobioside, named tricalysionoside A (1), and three sulfates, named sulfatricalysines A—C (2—4). Extensive isolation work on the 1-BuOH-soluble fraction of a MeOH extract of T. dubia yielded sulfatricalysines D—F (5—7) and three new ent-kaurane glucosides, named tricalysiosides X—Z (8—10). The structures of the new compounds were elucidated by analyses of one- and two-dimensional NMR spectroscopic data. The absolute stereochemistry of tricalysionoside A (1) was established by modified Mosher's method.
Icariside B5 is one of the widely distributed megastigmane glucosides among plant sources. The absolute structure of icariside B5 was reinvestigated by chemical conversion from the related compound and the application of the modified Mosher's method. As a result, the structure of icariside B5 was revised to be (6S,9S)-6,9-dihydroxymegastigman-4-en-3-one 9-O-β-D-glucopyranoside.