Dynamic stereochemistry of rutin (vitamin P) in solution: theoretical approaches and experimental validation

Rutin, vitamin P, was extracted from Salvia macrosiphon and identified by 1H, 13C, 1H–1H COSY, HMQC, and HMBC spectroscopy. In parallel, density functional theory (DFT) using B3LYP functional and split-valance 6-311G∗∗ basis set has been used to optimize the structures and conformers of rutin. Also experimental and theoretical methods have been used to correlate the dependencies of 1J, 2J, and 3J involving 1H and 13C on the C5″–C6″ (ω), C6″–O6″ (θ), and C1‴–O6″ (φ) torsion angles in the glycosidic moiety. New Karplus equations are proposed to assist in the structural interpretation of these couplings. 3JHH depends mainly on the C–C (ω) torsion angle, as expected, and 2JHH values depend on both C–C (ω) and C–O (θ) torsions. 1JCH values within hydroxymethyl fragments were also examined and found to depend on rCH, which is modulated by specific bond orientation and stereoelectronic factors. In all calculations solvent effects were considered using a polarized continuum model (PCM).

Graphical abstractThe 3D structure of vitamin P, an important bioflavonoid, has been studied in solution by 2D NMR spectroscopy and QM calculations.Figure optionsDownload full-size imageDownload as PowerPoint slide