Development of a rapid method to determine phenolic and other polar compounds in walnut by capillary electrophoresis-electrospray ionization time-of-flight mass spectrometry.
The aim of this work was to develop a capillary electrophoresis-mass spectrometry (CE-MS) method to identify and quantify phenolic and other related polar compounds in walnut samples. The extraction capacity of several solvent mixtures of phenolic compounds from walnut by conventional solid-liquid extractions was tested, and CE and electrospray ionization MS parameters were optimized. The finalized procedure is able to determine many well-known phenolic compounds present in walnuts and provide relevant information about the presence of minor polar compounds. A new compound in walnut ((2E,4E)-8-hydroxy-2,7-dimethyl-2,4-decadiene-1,10-dioic acid 6-O-beta-d-glucopiranosyl ester, [M-H](-) 403.161m/z) with a structure similar to glansreginins was also identified. Phenolic compounds correspond to 14-28% of total polar compounds quantified. Aglycone and glycosylated ellagic acid represent the principal components and account for 64-75% of total phenols in walnuts. However, the sum of glansreginins A, B and (2E,4E)-8-hydroxy-2,7-dimethyl-2,4-decadiene-1,10-dioic acid 6'-O-beta-d-glucopiranosyl ester was in the range of 72-86% of total quantified compounds. In addition, this is the first time that separation by CE with detection by electrospray ionization time-of-flight MS has been applied to the analysis of phenolic and other polar compounds in walnut samples, providing results in less than 15min.
Gómez-Caravaca
Ana M
AM
Department of Analytical Chemistry, University of Granada, c/Fuentenueva s/n, 18003 Granada, Spain.
Verardo
Vito
V
Segura-Carretero
Antonio
A
Caboni
Maria Fiorenza
MF
Fernández-Gutiérrez
Alberto
A
D019075:Electrophoresis, Capillary / Q000379:methods*; D031324:Juglans / Q000737:chemistry*; D010636:Phenols / Q000032:analysis*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D010636:Phenols