Cladanthus scariosus Essential Oil and Its Principal Constituents with Cytotoxic Effects on Human Tumor Cell Lines

Cladanthus is a small genus of the Asteraceae family comprising just five species that, apart from Cladanthus mixtus (L.) Chevall., has a large distribution in all the Mediterranean countries, mainly in the North Africa area. Several ethnopharmacological uses have been reported for species of this genus. Notably, Cladanthus scariosus (Ball) Oberpr. & Vogt is endemic to Morocco. Seeking to delve deeper into the phytochemistry and pharmacological aspects of this species, in this work, we investigated the essential oil (EO) obtained from the aerial parts of a locally sourced accession, hitherto unexplored, growing wild near Tizi n’Ticha, Morocco. The chemical composition of the EO, obtained by the hydrodistillation method, was evaluated by GC and GC-MS. The most abundant EO constituent was germacrene D (13.2%), the principal representative of the sesquiterpene hydrocarbons class (27.2%). However, the major class of constituents was monoterpene hydrocarbons (43.0%), with α-pinene (11.9%), sabinene (10.2%), p-cymene (8.5%), and α-phellandrene (5.2%) as the most abundant. The EO and its main constituents have been tested for their possible cytotoxic activity against three human tumor cell lines (MDA-MB 231, A375, and CaCo2) using the MTT assay, with corresponding IC₅₀ values of 13.69, 13.21, and 22.71 µg/mL, respectively. Germacrene D and terpinen-4-ol were found to be the most active constituents with IC₅₀ values between 3.21 and 9.53 µg/mL. The results demonstrate remarkable cytotoxic activity against the three human tumor cell lines studied, and in the future, further analyses could demonstrate the excellent potential of C. scariosus EO as an antitumor agent.