Teucrium fruticans L., a multi-scale study: from trichomes to essential oil

This work represents the first multi-scale study on Teucrium fruticans L. cultivated at the Ghirardi Botanic Garden (Lombardy, Northern Italy), combining a micromorphological and a phytochemical survey on the plant’s aerial parts. Micromorphological investigations highlighted the presence of five trichomes morphotypes, distinguished by a different distribution pattern: peltates, short-stalked and ball-like medium-stalked capitates, ubiquitous on the whole plant, medium-stalked and long-stalked capitates, exclusive to the floral whorls. Both peltates and medium-stalked capitates were recognized as the main terpene production sites. Phytochemical characterization focused on the essential oils, obtained by Clevenger-type hydrodistillation in February and April 2022, which resulted mainly formed by sesquiterpene hydrocarbons. The February EO profile was characterized by β-caryophyllene and germacrene D as main compounds, while in April β-myrcene was detected at high percentage in addition to the previous two components. Literature data, dealing with the biological activities of the main oil constituents, highlighted an anti-microbial, anti-inflammatory, and anti-tumor potential, due to the high content in sesquiterpenes and, particularly, of β-caryophyllene and germacrene D.