Abstract
Seseli tomentosum Vis. is an endemic species distributed along the eastern coast of the Adriatic Sea. In this study, the leaf structure as observed by light and electron microscopy, the phytochemical composition of the volatile organic compounds, and the cytotoxic activity of S. tomentosum are presented. The secretory ducts located above and within the phloem and below the xylem part of the vascular bundle represent the first description of the leaf secretory structures of S. tomentosum. The essential oil and hydrosol were extracted from air-dried leaves by Clevenger distillation and analyzed by gas chromatography-mass spectrometry, combined with headspace solid-phase microextraction of volatiles from the hydrosol and fresh plant material. α-Amorphene, β-caryophyllene, germacrene D, β-cadinene, and α-copaene were the most abundant sesquiterpenes in the essential oil and fresh plant material. Among the monoterpenes, α-pinene was most abundant in the essential oil, limonene in fresh plant material, and α-terpineol in the hydrosol. Moderate cytotoxic activity of the methanolic extract of S. tomentosum, with higher inhibition of cell division observed in the human cervical cancer and osteosarcoma cell lines, and weaker activity in the healthy retinal pigmented epithelial and colon cancer cell lines, was detected using the MTS-based assay. With these results, we aim to highlight the potential of endemic plants, emphasizing the importance of studying species such as S. tomentosum and their contributions to biodiversity and human health as sources of bioactive compounds.