Cytotoxic Triterpenoid Saponins Acetylated with Monoterpenoid Acid from Albizia julibrissin

Three new triterpenoid saponins, named julibroside J16 (2), julibroside J17 (3), and julibroside J21 (4), each of which possesses an oleanane triterpenoid aglycone of acacic acid, two monoterpenoid acids, and nine sugar moieties, together with one known saponin, julibroside II (1), were isolated from the stem bark of Albizia julibrissin by chromatographic methods. Their structures were established by chemical and spectroscopic means. Saponins 1, 2, and 4 showed inhibitory activities against Bel 7402 human cancer cell line in vitro.