title: Rapid and direct low micromolar NMR method for the simultaneous detection of hydrogen peroxide and phenolics in plant extracts.
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.
authors.affiliation: Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
authors.forename: Pantelis
authors.initials: P
authors.lastname: Charisiadis
authors.forename: Constantinos G
authors.initials: CG
authors.lastname: Tsiafoulis
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Exarchou
authors.forename: Andreas G
authors.initials: AG
authors.lastname: Tzakos
authors.forename: Ioannis P
authors.initials: IP
authors.lastname: Gerothanassis
mesh_terms: D002934:Cinnamates / Q000032:analysis; D005419:Flavonoids / Q000032:analysis; D006861:Hydrogen Peroxide / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008832:Microchemistry / Q000379:methods*; D039821:Monoterpenes / Q000032:analysis; D031341:Origanum / Q000737:chemistry; D010636:Phenols / Q000032:analysis*; D035261:Plant Components, Aerial / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry*; D013997:Time Factors
chemical_list: D002934:Cinnamates; D005419:Flavonoids; D039821:Monoterpenes; D010636:Phenols; D010936:Plant Extracts; D006861:Hydrogen Peroxide