Study on the histochemical localization of essential oil and evaluation of the chemical profiles of wild populations of Salvia nemorosa L.

Salvia nemorosa L. is a widely distributed but comparatively understudied Salvia species. This work investigated the tissue localization of lipophilic constituents and profiled essential oil (EO) composition of wild Bulgarian populations. Stems were hand-sectioned and stained with Sudan III to visualize lipid deposits by light microscopy. EOs isolated from the collected flowering aerial parts from four sites were obtained by 4 h hydrodistillation and analyzed by gas chromatography–mass spectrometry (GC–MS); constituents were identified by RI and library match. Results: Sudan III staining revealed abundant red–orange lipid droplets distributed throughout the internal and epidermal tissues, including within the glandular trichomes. Across sites, 31–45 volatile compounds were identified, representing 91.96–97.71% of the total oils. Profiles were dominated by sesquiterpenes: germacrene D (17.64–41.34%) and β-caryophyllene (9.50–22.38%) were major constituents, with site-specific contributions of sabinene (up to 21.89%) and bicyclogermacrene (up to 7.67%). Sesquiterpene hydrocarbons (SH) comprised 50.96–70.81% of each EO, followed by oxygenated sesquiterpenes (8.19–25.58%). Monoterpenes were present in low concentrations in all samples, except for the Ivan Vazovo EO sample. Conclusion: Salvia nemorosa L. from Bulgaria exhibits SH-dominant chemotypes with marked geographic variation. The high levels of germacrene D and β-caryophyllene support the species as a potential source of bioactive sesquiterpenes and merit further biological evaluation.