Essential oil chemotypification and secretory structures of the neglected vegetable Smyrnium olusatrum L. (Apiaceae) growing in central Italy

As part of our research on local plants, including neglected horticultural crops to be rediscovered as culinary vegetables, we focused on Smyrnium olusatrum, a biennal herb used in cuisine for many centuries by Romans that has now been replaced by celery. We investigated the essential oil compositions of different plant organs collected in 18 populations of central Italy (Marche, Umbria, Abruzzo, Tuscany and Latium) by gas chromatography (GC) with a flame ionization detector and GC with mass spectrometry (MS) to identify the main chemotypes that occur. Owing to the presence of thermosensitive molecules such as isofuranodiene, curzerene and germacrone undergoing Cope-rearrangement during the GC run, a truthful quantitative determination of these constituents was accomplished by high-performance liquid chromatography with a diode-array detector (HPLC-DAD). Chemical data were supported by a chemometric technique in the form of principal component analysis, which allowed identification of chemical differences among organs. Furanosesquiterpenoids were the main fraction of the oils, with isofuranodiene as the most abundant in flowers and roots, furanoeremophil-1-one in leaves and roots and 1-β-acetoxyfuranoeudesm-4(15)-ene in fruits. To complete the phytochemical analysis, polar compounds such as chlorogenic acid, isoquercitin, 3-indoleacetic acid and saccharose were isolated from the ethanolic extracts of the plant by column chromatography and structurally elucidated by nuclear magnetic resonance. Moreover, a morphological and histochemical survey on the secretory structures was performed, with the special aim to localize the sites of terpenes biosynthesis in both above- and belowground organs. Overall, the results can be considered important in the light of the recent interest in neglected edible plants for botanical food supplements and functional foods market.