Geographical patterns of in vivo spontaneously emitted volatile organic compounds in Salvia spp.

The genus Salvia is part of the family of the Lamiaceae, comprising almost 1000 different species that make it the largest one in this family; it includes annual, biennial and perennial specimens. It shows a wide variety of characteristics in the specimens, both in the external appearance and the volatile organic compounds (VOCs) profiles. Such a wide number of species is due to the almost ubiquitous origin of this genus, but also to the cultivars selection carried out by botanists and private collectors during centuries. In this work, we analysed the spontaneous volatile emission profiles of living samples to evaluate the existence of possible patterns and to find out possible parameters that lead to such patterns. We carried out the analysis on living samples of leaves taken from 30 species of Salvia obtained from a large collection, which has been bestowed the title of “collection of national relevance” by the Italian Botany Society, located at the Botanical Garden of the University of Pisa. Within the collected samples, 14 are specimens whose natural habitat is the Mediterranean Europe and Middle East regions, 14 species have their native environment in the Central and Southern America, and 2 come from South Africa. The sampling was carried out using the Head Space - Solid Phase Micro Extraction technique. The captured volatile organic compounds were then characterized by GC-MS. We carried out a Multivariate Statistical Analysis on the results to show possible relevant patterns: we found out that the spontaneous volatile emission profiles differ significantly accordingly to the geographical origin of the various species. This permitted to hypothesize that the environment plays a fundamental role in Salvia secondary metabolites production: the volatile fraction, in particular, represents the reaction of the specimen to the particular local environment (temperature, humidity, latitude, altitude, pollinators, enemies…), making it a very specific chemotaxonomical marker. These results, once improved with a wider number of specimens analyses, could be used as a method to identify the origins of unknown cultivars and wild Salvia species. At present, the dietary and pharmacological use of Salvia is restricted to a small number of species. This genus exhibits a largely variable thujones (α- and β-thujone) content, which determines the edibility and the potential human toxicity if used in dietary and pharmacological supplements or in essential oil form. Thujone toxicity has been widely studied and its intake can result in neurotoxicity, both acute and chronic: it inhibits GABAA receptors, inducing dose-dependent excitation and convulsions. This becomes especially important in assessing the safety of use in children: in 2011 a report showed the case of a child and a newborn who experienced generalized tonic-clonic seizures after an accidental exposure to sage essential oil. In this study, we also investigated the collected leaves samples to assess the presence (or the lack of) thujone in the spontaneously emitted volatile fraction. We found specimens without thujone, thus making them suitable possible candidates for food and pharmacological use. Furthermore, the different aromatic profiles could suggest different uses of the various species as spices.