Verbenone

An n-alkane (C 7 -C 25 ) mixture was analyzed under the same experimental GC/MS conditions to calculate the retention indices (RIs). Identification of EO components was performed by comparing their mass spectra on both columns with those listed in the commercial mass spectral libraries NIST and Wiley 275 computer libraries, our home-made library constructed with pure compounds, and those from literature [21, 22] , allowing a reliable confirmation of the identity of each component. A further identification was accomplished by comparing their RIs on both polar and apolar columns relative to the retention times of the series of n-alkanes (C 7 -C 25 ) with those from literature [21, 23] or with those of standard compounds available in our laboratories, obtained from Sigma-Aldrich (Germany). Standards of some EOs of known composition (such as the EO of Rosmarinus officinalis L. from Phytosun Aroms, Plélo, France) were also injected in similar conditions for the comparison of retention times (t R ) and mass spectra. In addition, the following standards were purchased from Sigma-Aldrich: α-pinene, camphene, β-pinene, myrcene, limonene, borneol, terpinen-4-ol, α-terpineol, verbenone, bornyl acetate, β-caryophyllene, γ-cadinene, δ-cadinene, caryophyllene oxide, α-cadinol, and β-bisabolol. Relative proportion of each compound was determined from the GC peak areas.

The analytical standards n-hexanal, n-nonane, α-pinene, camphene, benzaldehyde, β-pinene, 1octen-3-ol, p-cymene, limonene, γ-terpinene, terpinolene, linalool, trans-thujone, trans-pinocarveol, terpinen-4-ol, α-terpineol, myrtenol, verbenone, n-decanal, geraniol, geranial, (E)-caryophyllene, αhumulene, (E)-β-ionone, (E)-nerolidol, caryophyllene oxide, n-hexadecanoic acid were purchased from SigmaAldrich (I-Milan) and used for identification of some peaks; (E)-Phytol was previously isolated from Onosma echioides (Maggi et al., 2009) . A mixture of n-alkanes (C8-C30) was purchased from Supelco (Bellefonte, PA) and used to calculate the temperature-programmed retention indices of chromatographic peaks. n-Hexane was purchased from Carlo Erba (I-Milan).