Essential Oils Diversity of Teucrium Species

The Mediterranean flora is characterized by an abundance of aromatic plants. These plants make a significant contribution to the Mediterranean ecological communities both in terms of species numbers and biomass. In this area, Teucrium is a polymorphic and cosmopolitan genus of perennial plants, the largest of the Lamiaceae family, which comprises more than 300 species, of which almost 50 are native to Europe. The members of this genus are commonly known as germanders: they are bitter, astringent and antirheumatic herbs, utilized as antispasmodic agents for gastric ulcer and intestinal inflammation, as diuretic, antiseptic, antipyretic and antihelmintic agents. Moreover, they were also used in food preparation. Teucrium species are rich in essential oils and the presence of various biologically active monoterpenoid and sesquiterpenoid with several biological activities has been reported. This review summarizes the chemical features of the essential oils of Teucrium species reported in literature: it provides an overview on their compositions with particular reference to the more abundant components and to the reported biological activities. Teucrium polium, T. chamaedrys, T. flavum and T. capitatum are the most studied taxa concerning the volatile oil composition. Moreover, it is possible to distinguish different types of essential oils, characterized by the prevalence of a specific class of compounds: in particular, we recognized volatile oils rich in caryophyllene and caryophyllene derivatives, α- and β-pinene, germacrene B and D, α-, γ-, δ-cadinene and/or cadinol, limonene, and bisabolol/bisabolene. This richness in chemodiversity confers to the essential oils from Teucrium species distinctive biological properties and applications, often confirming the traditional and folk uses of this genus. This review testifies the high great variability of Teucrium essential oils and shows that the possible factors responsible for the chemical polymorphism of essential oils and consequently for their bioactivity need further investigatio