ChemInform Abstract: Astertarone B, a Hydroxy-Triterpenoid Ketone from the Roots of Aster tataricus L.

Abstract

The roots of Aster (A.) tataricus L. (Compositae) are used as the Chinese crude drug Asteris Radix (Japanese name: shion) and are combined in various traditional Chinese prescriptions for use as cough medicines, expectorants and diuretics 1) . Constituents of the root extracts have been investigated, and the presence of a triterpenoid ketone, shionone (shion-21-en-3-one), 2—4) seven triterpenoid glycosides, aster saponins A—G, 5—7) and three monoterpenoid glycosides, shionosides A—C, 7,8) have been reported. Our recent study on the methanol extract of A. tataricus roots has led to the isolation and structural elucidation of a new triterpenoid ketone, astertarone A (D: A-friedoeuph-21-en-3-one), along with epishionol (shion-21-en-3b -ol). 9) In this paper, we report the isolation and characterization of yet another new triterpenoid ketone, designated astertarone B (1), in addition to spinasterone [(22E)-5a-stigmasta-7,22-dien-3-one], from the extract. Column chromatography of the hexane soluble portion of the methanol extract of A. tataricus roots on silica gel afforded a triterpenoid ketone fraction. Crystallization of the ketone fraction from acetone‐methanol, followed by preparative HPLC of the filtrate portion, eventually yielded compound 1 and spinasterone. Identification of spinasterone was performed by spectral comparison with an authentic compound. Compound 1, with a molecular formula of C30H50O2 determined from its high-resolution mass spectrum (HR-MS) (M 1 , m/z 442.3836), gave IR absorptions at 3473 (hydroxyl group), 1712 (ketone), and 833 cm 21 (trisubstituted double bond). Compound 1 displayed two olefinic methyl singlets at d 1.61 and 1.69, with an olefinic methine signal at d 5.10 (br t, J57.0 Hz), which correspond to one isopropylidene group, and six tertiary methyl singlets at d 0.82, 0.89, 0.90,