title: The bioactivity-guided isolation and structural identification of toxic cucurbitacin steroidal glucosides from stemodia kingii.
abstract: A histologically validated murine model for the ovine intoxication by Stemodia kingii was used as a bioassay to guide the isolation of several groups of toxins from Stemodia kingiL Two of the toxins from one group were purified sufficiently to allow structural analysis and a determination of their median lethal doses (LD50) for oral administration to mice. A combination of acid hydrolysis, elemental analysis, HPLC-MS, 1D-NMR (1H, 13C) and 2D-NMR (1H-1H COSY, 13C-1H HSQC and HMBC, and gNOESY) was used to define stemodiosides B3 and B4 as cucurbitacin steroidal glucosides. Thus stemodioside B3 is (24Z)-3 alpha-(beta-glucopyranosyloxy)-2 beta,20,27-trihydroxy- 19-(10 -9 beta)-abeo-10alpha-lanost-5,24-diene- 11-one and stemodioside B4 is (23E)-3 alpha-(beta-glucopyranosyloxy)-20,20,22,27-tetrahydroxy- 19-( 10-9 beta)-abeo- 10 alpha-lanost-5,23-diene- 11-one. The approximate oral LD50s for stemodiosides B3 and B4 in mice were estimated to be 99 and 42 mg/kg body weight, respectively.
authors.affiliation: Department of Agriculture, 3 Baron-Hay Court, South Perth, Western Australia 6151, Australia.
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Allen
authors.forename: Steven M
authors.initials: SM
authors.lastname: Colegate
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Mitchell
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Mulder
authors.forename: Merl F
authors.initials: MF
authors.lastname: Raisbeck
mesh_terms: D000818:Animals; D001681:Biological Assay; D054728:Cucurbitacins; D008401:Gas Chromatography-Mass Spectrometry; D005960:Glucosides / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular; D028083:Scrophulariaceae / Q000737:chemistry*; D013237:Stereoisomerism; D013256:Steroids / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D014315:Triterpenes / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D014904:Western Australia
chemical_list: D005960:Glucosides; D013256:Steroids; D014315:Triterpenes; D054728:Cucurbitacins