The Cytotoxic Effects on Tumor Cell Lines of Thymus zygis subsp. gracilis Essential Oil and its Principal Constituents

Thymus zygis subsp. gracilis is an aromatic plant endemic to Morocco and Spain where it is used in the folk medicine. In this work, the essential oil (EO) composition of wild Moroccan accessions has been investigated by GC and GC-MS. The chromatogram showed the occurrence of oxygenated monoterpenes, with thymol (29.5%), carvacrol (10.6%), and linalool (7.2%) as the most abundant components; monoterpene hydrocarbons (15.2%), and sesquiterpene hydrocarbons (12.5%), were less abundant with p-cymene (10.6%) and caryophyllene (8.3%) as the most representatives. 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 CaCo-2), with corresponding IC50 values of 31.10, 27.97, and 33.32 µg/mL, respectively. Carvacrol and caryophyllene resulted in the most active constituents. The results demonstrate a good cytotoxic activity against several tumors and suggest that T. zygis subsp. gracilis EO could be regarded as a natural bioactive source.