Identification of the Volatile Components of Galium verum L. And Cruciata leavipes Opiz from the Western Italian Alps

The chemical composition of the volatile fraction from Galium verum L. (leaves and flowers) and Cruciata laevipes Opiz (whole plant), Rubiaceae, was investigated. Samples from these two plant species were collected at full bloom in Val di Susa (Western Alps, Turin, Italy), distilled in a Clevenger-type apparatus, and analyzed by GC/FID and GC/MS. A total of more than 70 compounds were identified, making up 92%–98% of the total oil. Chemical investigation of their essential oils indicated a quite different composition between G. verum and C. laevipes, both in terms of the major constituents and the dominant chemical classes of the specialized metabolites. The most abundant compounds identified in the essential oils from G. verum were 2-methylbenzaldheyde (26.27%, corresponding to 11.59 μg/g of fresh plant material) in the leaves and germacrene D (27.70%; 61.63 μg/g) in the flowers. C. laevipes essential oils were instead characterized by two sesquiterpenes, namely β-caryophyllene (19.90%; 15.68 μg/g) and trans-muurola-4(15),5-diene (7.60%; 5.99 μg/g); two phenylpropanoids, benzyl alcohol (8.30%; 6.71 μg/g), and phenylacetaldehyde (7.74%; 6.26 μg/g); and the green-leaf alcohol cis-3-hexen-1-ol (9.69%; 7.84 μg/g). The ecological significance of the presence of such compounds is discussed.