Sage at the botanic garden: essential oils and VOC emission related to micromorphological characterization

In this work we studied four sage species (Salvia verticillata, S. uliginosa, S. blepharophylla, S. greggii) preserved at the Ghirardi Botanic Garden of the Milan University. Micromorphological observations on glandular trichomes were firstly related to the spontaneous emission of Volatile Organic Compounds (VOCs) from both flowers and leaves, since volatiles could act as attractors for pollinators or deterrents for herbivores/pathogens (phytocentric perspective). The composition of the essential oils (EOs) was then taken into consideration, paying special emphasis to the potential importance for humans (anthropocentric perspective). Phytochemical survey revealed that the overlapping of VOCs between the Head-Space and EOs profiles ranged from 25.0% in S. verticillata up to ca 65.0% in the other species. Sesquiterpene hydrocarbons were the dominant compound class in all of the HS-SPME (28.3 – 90.1%) and EOs profiles (30.6 – 79.6%), with the exception of the floral profiles of S. blepharophylla and S. greggii, where monoterpene hydrocarbons (74.8%) and oxygenated monoterpenes (66.4%) prevailed, respectively. As a whole, the most abundant components of VOCs were consistent with the major compounds of EOs within each Salvia species. Among the principal compounds, β-caryophyllene, germacrene D, bicyclogermacrene, 1,8-cineole and γ-muurolene are common deterrents with a documented inhibiting growth effect towards bacteria or larvae of insects [1,2]. Conversely, an attractive role towards pollinators is hypothesized only for β-caryophyllene, but documented literature data lack. The therapeutic potential value of EOs in S. uliginosa and S. verticillata could be due to the presence of β-caryophyllene and γ-humulene (total relative amount ca 12.0%), with well-known anti-inflammatory properties [3].