Revisiting the Cyclocephagenols via Astragalus condensatus: Structural Insights and Configurational Revision

J Nat Prod. 2024 Nov 22;87(11):2657-2664. doi: 10.1021/acs.jnatprod.4c00751. Epub 2024 Oct 26.

Abstract

The phytochemical investigation of the MeOH extract of Astragalus condensatus roots led to the discovery of a new tetrahydropyran cycloartane-type triterpenoid, astracondensatol A (1), alongside six known cyclocephagenol derivatives (2, 3, 20, 32, 35, and 36). Elucidation of their structures involved 1D and 2D-NMR spectroscopy and mass data analysis. Upon comparing NMR spectroscopic data with prior literature, several carbon shift anomalies, particularly at C-24, prompted a reevaluation using quantum chemical calculations, resulting in the revision of the 24S to 24R absolute configuration for compound 2 and 38 other reported cyclocephagenol-type triterpenoids. X-ray crystallography data further supported the analysis in establishing the absolute configuration of compound 2. Ambiguous NOE correlations and publication bias could have played a significant role in miss-assigning the C-24 absolute configuration in tetrahydropyran cycloartane-type triterpenoids.

MeSH terms

  • Astragalus Plant* / chemistry
  • Crystallography, X-Ray
  • Magnetic Resonance Spectroscopy
  • Molecular Conformation
  • Molecular Structure
  • Plant Roots / chemistry
  • Triterpenes* / chemistry

Substances

  • Triterpenes
  • cycloartane