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Variable-temperature ¹H-NMR studies on two C-glycosylflavones
Julia H Frank1, Yomica L Powder-George, Russel S Ramsewak
1Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago, West Indies.
Molecules (Basel, Switzerland)
|July 4, 2012
Summary
Two C-glycosylflavones, swertisin and embinoidin, from Anthurium aripoense leaves exist as two rotamers in solution. Variable-temperature NMR and computational studies confirmed their interchange via rotation around the C-glycosidic bond.
Area of Science:
- Natural Product Chemistry
- Organic Chemistry
- Spectroscopy
Background:
- C-glycosylflavones are a class of plant secondary metabolites with potential biological activities.
- Anthurium aripoense is a plant species from which bioactive compounds can be isolated.
Purpose of the Study:
- To isolate and characterize C-glycosylflavones from Anthurium aripoense leaves.
- To investigate the solution-state conformational dynamics of isolated C-glycosylflavones.
Main Methods:
- Isolation and purification of compounds using chromatographic techniques.
- Structure elucidation using 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy.
- Variable-temperature (VT) ¹H-NMR studies to assess dynamic processes.
- Transverse-spatial Relaxation (T-ROESY) NMR experiments.
- Molecular mechanics (MM2) calculations using Chem3D Pro software.
Main Results:
- Two known C-glycosylflavones, swertisin and embinoidin, were successfully isolated and identified.
- NMR spectra at room temperature showed signal doubling, indicating the presence of two distinct rotamers.
- VT ¹H-NMR studies confirmed the dynamic nature of these rotamers.
- T-ROESY data and MM2 calculations provided evidence for interconversion between rotamers through rotation around the C-glycosidic bond.
Conclusions:
- Swertisin and embinoidin exist as an equilibrium mixture of two rotamers in solution.
- The observed rotameric interconversion is driven by rotation about the C-glycosidic bond.
- This study provides insights into the conformational flexibility of C-glycosylflavones in solution.
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