Gas Chromatography-Ion Mobility Spectrometry for Characterizing Different Species of Origanum and Detecting Blends of Its Products

Abstract Origanum spp. are aromatic herbs with leaves rich in essential oils. The dried leaves of some species are known as oregano and are widely used as culinary herbs. This study evaluates headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) for profiling the volatilome of Origanum and for detecting blends with nonoregano leaves. Five (sub)species were cultivated under controlled conditions and analyzed over 6 weeks using HS-GC-IMS, supported by mass spectrometry (MS) for identification. The method showed good repeatability (RSD < 5%), acceptable intermediate precision (RSD < 12.8%), and the plants exhibited a stable profile over 6 weeks. Clear differences among species in their content of carvacrol/thymol and sesquiterpenes are shown. To assess authenticity, ground oregano was blended with marjoram, myrtle, thyme, olive, or hoary rock-rose leaves, but possible marker substances can only be found for marjoram and myrtle. However, the results demonstrate that HS-GC-IMS is a sensitive, cost-effective tool for characterizing the volatilome in Origanum and for detecting selected adulterants.