Determination of 2,5-Diketopiperazines Iin Greek Processed Olives by Liquid Chromatography/Mass Spectrometry Analysis

Sotirios M. Bratakos¹, Panagiotis Zoumpoulakis², Eleni Siapi², Kyriakos Riganakos³, and Vassilia J. Sinanoglou^1*

¹Laboratory of Chemistry, Analysis and Design of Food Processes, Instrumental Food Analysis, Department of Food Technology, Technological Educational Institution of Athens, Ag. Spyridonos, 12210, Egaleo, Greece
²Institute of Biology, Medicinal Chemistry and Biotechnology, National Hellenic Research Foundation, Vas. Constantinou Ave., 11636, Athens, Greece
³Laboratory of Food Chemistry and Technology, Department of Chemistry, University of Ioannina, 45110, Ioannina, Greece

Corresponding Author Email: vsina@teiath.gr

Diketopiperazines (DKPs) are cyclic dipeptides which have been detected in a variety of natural products, especially in thermally treated or fermented foods and beverages, providing a metallic bitter taste. DKPs, mainly due to their characteristic heterocyclic system, have been reported to exhibit a broad spectrum of biological activities including antimicrobial, antiviral, antitumor, antihyperglycaemic and antimutagenic. In the present study, several DKPs were identified in seven different Greek varieties of processed olives using HR-LC-MSⁿ. The identification of DKPs in olive samples was achieved by comparison of their retention time and fragmentation pattern with reference DKP standards. The MSⁿ spectra were identical to confirm the presence of specific compounds because their results associate both fragmentation pattern and fragments’ intensity. Nine compounds were found out of a total of 19 standard DKPs. The most prominent diketopiperazine was the cyclo(Phe-Phe) followed by and cyclo(Phe-Pro). Varieties where most DKPs were identified were Kothreiki, Kalamon, Throumpoelies and Helidoni.

2,5-diketopiperazines; HR-LC-MSⁿ; olives; fragmentation pattern

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