Identification of phenolic compounds in almond (Prunus dulcis) and pecan (Carya illinoinensis) extracts by liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS)

Abstract

Almonds and pecans are considered functional foods because their regular intake provides protection against several chronic-degenerative diseases. Phenolic compounds are some of the most bioactive components of these tree nuts; yet, their identification and characterization is regularly viewed as an analytical challenge. The aim of the present work was to characterize the phenolic compound profile of acetone and methanol extracts of almond and pecan nut, by using HPLC coupled to tandem mass spectrometry (MS/MS). First, high resolution MS (Q-TOF) was used to identify phenolic compounds in the extracts: 29 compounds were detected in almond (22 in acetone extract, 24 in ethanol extract) and 43 in pecan (39 in acetone extract, 37 in ethanol extract). Identity of 6 almond compounds and 20 pecan compounds was confirmed through analysis of their MS/MS fragmentation patterns. Phenolic profiles were different between pecan and almond but similar between extraction solvents for a same tree nut species. Flavonols and flavanones were the major types of phenolic compounds in almond, while pecan phenolics were mostly hydrolysable (ellagitannins acid ellagic acid derivatives) and condensed tannins (upto tetramers). Three ellagitannins are described for the first time in pecan.