Chemical classification of the essential oils of the Iranian Salvia species in comparison with their botanical taxonomy

The essential oils of eight Salvia species collected from different localities in Iran were analyzed by gas chromatography/mass spectrometry (GC/MS). The analytical results were compared with those previously published for related Iranian sage species in order to identify chemical markers for these species. Salvia eremophila, S. hypoleuca, and S. reuteriana are endemic, while S. atropatana, S. chloroleuca, S. santolinifolia, S. aegyptiaca, and S. macrosiphon also grow wild in neighboring countries. We categorized the Iranian Salvia species into four main chemotypes according to their essential-oil constituents: those which are dominated by 1) monoterpenes, 2) mono- and sesquiterpenes, or 3) sesquiterpenes as the major constituents, and 4) those containing low-molecular-weight acids, aldehydes, and esters, and green-leaf volatiles (GLVs). Likely due to the chemical diversity of different Salvia chemotypes, this categorization was supported by principal component analysis (PCA) for the group sampled here, but not for the values reported in the literature. We identified the following chemical markers: α-pinene, β-pinene, 1,8-cineol, linalool, and borneol in monoterpene-rich species, or β-caryophyllene, germacrene D, bicyclogermacrene, spathulenol, and caryophyllene oxide in sesquiterpene-rich species. Among these, α-pinene, β-caryophyllene, and germacrene D are the most common and abundant in the Salvia species investigated. In accordance with their close biological taxonomy, the chemical similarity of the essential oils of S. santolinifolia and S. eremophila is so high that we may consider them chemically identical.