Triterpene glucosides of <Emphasis Type="Italic">Astragalus</Emphasis> and their genins. LXXIV. Cyclotrisectoside,the first trisdesmoside of cyclocephalogenin

The two trisdesmoside cycloartane glycosides astragaloside VII and cyclotrisectoside were isolated from Astragalus dissectus (Leguminosae) and identified. The latter was 20R,25-epoxy-24S-cycloartan-3β,6α,16β,24-tetraol 3-O-β-D-xylopyranoside-6,24-di-O-β-D-glucopyranoside and was a new natural compound. Presented at the Sixth International Symposium on the Chemistry of Natural Compounds (SCNC, Turkey, Ankara, 28–29 June 2005). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 132–134, March–April, 2007.     

Triterpene Glycosides of Astragalus and Their Genins. LXVI. Cycloorbicoside C, a New Bisdesmoside

The new triterpene glycoside cycloorbicoside C was isolated from the aerial parts of Astragalus orbiculatus Ledeb. (Leguminosae) and was identified as (23R,24S)-16,23;16,24-diepoxycycloartan-3,25-diol 3-O--D-xylopyranoside 25-O--D-glucopyranoside.     

A novel editing technique for F MRI: Molecule-specific imaging

A novel technique is proposed to facilitate the selective imaging of specific molecules from a mixture. The application of the technique presented here demonstrates the ability to selectively produce ¹⁹F MR images of either trifluoroacetic acid or the perfluorocarbon emulsion Oxypherol-ET (perfluorotributylamine), when both molecules are present simultaneously. Selective detection is based on the presence of homonuclear J-modulation in one molecule and differential spin-spin relaxation time (T₂). Perfluorotributylamine, an A₃B₂ system, is subject to homonuclear J-modulation, which produces a null signal from the antiphase components of the triplet (A₃) when an echo time is used in a spin-echo image. At this echo time the second molecule, in this example trifluoroacetic acid, a non-coupled spin system, is selectively imaged. At longer echo times, e.g., TE = 1/J there is substantial recovery of the J-modulated signal, which may be solely observed due to T₂ decay of the trifluoroacetic acid signal. The method is demonstrated both using phantoms and in vivo.     

Triterpene Glycosides of Astragalus and Their Genins. LXVII. Structure of Cycloexoside B

Another seven components from the roots of Astragalus exilis A.Kor. (Leguminosae) were identified using spectral data and chemical transformations. A triterpenoid of genin nature was identical to cyclosiversigenin. One compound of glycosidic nature turned out to be a new cycloartane glycoside called by us cycloexoside B of structure 20R,24S-epoxycycloartan-3,6,16,25-tetraol 3-O--D-(2-Oacetyl) xylopyranoside. Five glycosides were identified as cyclosiversigenin 3-O--D-xylopyranoside and cyclosiversiosides B, C, D, and G.     

Triterpene Glycosides from <Emphasis Type="Italic">Astragalus</Emphasis> and Their Genins. LXXI. Cycloorbicoside D,a New Glycoside from <Emphasis Type="Italic">Astragalus orbiculatus</Emphasis>

The new cycloartane glycoside cycloorbicoside D, which has the structure 23ξ,24ξ-cycloartan-3β6α,16β,23,24,25-hexaol 3-O-β-D-xylopyranoside, was isolated from the aerial part of Astragalus orbiculatus Ledeb. (Leguminosae). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 345–346, July–August, 2005.     

Triterpene Glycosides and Their Genins from Astragalus. LXIX. Orbigenin, the First Lanostanoid from Astragalus Plants

The new lanostane methylsteroid orbigenin, the structure of which is 23,24-lanost-9(11)-en-3,7,16,19,23,24,25-heptaol, was isolated from Astragalus orbiculatus Ledeb. (Leguminosae). The structure of the new triterpenoid, the first lanostanoid from plants of the Astragalus genus, was determined using electron-impact mass spectrometry and PMR and ¹³C NMR spectroscopies interpreted using J-modulation, DEPT, and the 2D NMR methods: ¹H-¹H COSY, HSQC, and HMBC.