Direct characterization of adulterated oregano leaves by atmospheric pressure maldi mass spectrometry

Economically motivated adulteration (EMA) of herbs and spices is a matter of great concern for consumers, producers, and regulators alike. EMA is a widespread practice that involves the deliberate addition of inexpensive substances to herbs and spices for economic benefit [1]. Accordingly, dried oregano appears to be the most vulnerable herb and it is suspected that approximately 48% of commercial samples may be adulterated [2]. Ambient mass spectrometry (AMS) methods analyze unprocessed or minimally modified solid samples enabling the rapid, economic and accurate analysis with minimal sample preparation [3]. In this project, a direct, rapid, and non-targeted method is proposed for classifying oregano samples using atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (AP-MALDI-MS) to distinguish between authentic oregano and its adulterants. This pilot study aimed to determine the chemical profiles of various oregano samples, including the most common adulterants such as sumac, olive, savory, strawberry tree, and myrtle. The AP-MALDI-MS fingerprints were acquired in both positive and negative ion modes and the two resulting data sets were pre-processed and submitted to supervised partial least squared discriminant analysis (PLS-DA) in order to discriminate the authentic oregano from the adulterants.