CORRELATIONS BETWEEN HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC RETENTION, X-RAY STRUCTURAL AND C-13 NMR SPECTROSCOPIC DATA OF FLAVONOID COMPOUNDS

The retention behaviour of selected flavonoid compounds was analysed and correlated with structural properties, as elucidated by X-ray crystallographic and C-13 NMR spectroscopic studies. A detailed analysis of group retention contribution (DELTA-log k') makes it possible to establish how the introduction of an OH group in the molecule affects the overall solute polarity and, therefore, its retention, in relation to the position of the OH group and the molecular environment. X-ray structural information and C-13 NMR chemical shifts show the formation of strong intramolecular hydrogen bonding (HB) in 5-hydroxy-flavones and a weaker intramolecular HB in 3-hydroxy-substituted compounds. DELTA-log k' values may be explained in terms of these intramolecular HB properties; moreover a quantitative relationship between DELTA-log k' values and chemical shifts was found.