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Published on: October 2, 2016
Rapid and direct low micromolar NMR method for the simultaneous detection of hydrogen peroxide and phenolics in plant
Pantelis Charisiadis1, Constantinos G Tsiafoulis, Vassiliki Exarchou
1Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
Abstract:
A rapid and direct low micromolar ¹H NMR method for the simultaneous identification and quantification of hydrogen peroxide and phenolic compounds in plant extracts was developed. The method is based on the highly deshielded ¹H NMR signal of H₂O₂ at ∼10.30 ppm in DMSO-d₆ and the combined use of picric acid and low temperature, near the freezing point of the solution, in order to achieve the minimum proton exchange rate. Line widths of H₂O₂ below 3.8 Hz were obtained for several Greek oregano extracts which resulted in a detection limit of 0.7 μmol L⁻¹. Application of an array of NMR experiments, including 2D ¹H-¹³C HMBC, spiking of the samples with H₂O₂, and variable temperature experiments, resulted in the unequivocal assignment of H₂O₂ precluding any confusion with interferences from intrinsic phenolics in the extract.
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