31P nuclear magnetic resonance spectroscopy of polyphenol-containing olive oil model compounds

Phosphitylation of the free hydroxyl and carboxyl groups of a series of polyphenol-containing olive oil model compounds with 2-chloro-4,4,5,5-tetramethyl-dioxaphospholane allows their classification on the basis of P-31 NMR chemical shifts. Unambiguous assignment of the P-31 NMR chemical shifts of the dihydroxy- and polyhydroxy-phenols has been achieved by employing one and two-dimensional NMR techniques. Furthermore, integration of the appropriate signals of the hydroxyl derivatives in the corresponding P-31 NMR spectra allows the quantification of these compounds. This study forms the basis for the development of a novel and sensitive method that can be used to obtain valuable information about polyphenols that are present in olive oils.