Identification and quantification of caffeic and rosmarinic acid in complex plant extracts by the use of variable-temperature two-dimensional nuclear magnetic resonance spectroscopy
Identification and quantification of caffeic and rosmarinic acid in complex plant extracts by the use of variable-temperature two-dimensional nuclear magnetic resonance spectroscopy
(EN)
Exarchou, V.
(EN)
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
(EL)
Exarchou, V.
(EN)
A combination of advanced nuclear magnetic resonance (NMR) methodologies for the analysis of complex phenolic mixtures that occur in natural products is described, with particular emphasis on caffeic acid and its ester derivative, rosmarinic acid. The combination of variable-temperature two-dimensional proton-proton double quantum filter correlation spectroscopy (H-1-H-1 DQF COSY) and proton-carbon heteronuclear multiple quantum coherence (H-1-C-13 HMQC) gradient NMR spectroscopy allows the identification and tentative quantification of caffeic and rosmarinic acids at 243 K in extracts from plants of the Lamiaceae family, without resorting to previous chromatographic separation of the components. The use of proton-carbon heteronuclear multiple bond correlation (H-1-C-13 HMBC) gradient NMR spectroscopy leads to the complete assignment of the correlations of the spins of H-2a and H-3a with the ester and carboxyl carbons of rosmarinic and caffeic acid, even at room temperature, and confirms the results of the above methodology. Quantitative results are in reasonable agreement with reverse phase HPLC measurements.
(EN)
