**Abstract**

Natural products are commonly used for developing anticancer drugs that are beneficial for various cancer types. The aim of this study is to apply *Colchicum umbrosum* Steven and *Colchicum baytopiorum* CD Brickell (one of the endemic species in Turkey) extracts on HeLa cell lines and determine changes in cytotoxicity and viability. For this aim, kinetic parameters such as proliferation rate have been determined by MTT assay, and apoptotic index (AI) has been researched by fluorescence microscopies using DAPI staining. Also, some apoptosis-related genes have been examined by the RT-PCR method. Five different concentrations of both extracts from the two Colchicum species have cytotoxic effects and it has been understood that HeLa cells were more sensitive to the most effective concentration of the *C. baytopiorum* extract, which is 0.1 mg/ml, and it showed antitumor effects by causing apoptosis for 48 h. The cytotoxic activity and apoptotic effects of *Colchicum umbrosum* Steven and *Colchicum baytopiorum* (Colchicaceae/Liliaceae) have been studied for the first time on HeLa cell lines. We suggested that the medicines derived from natural products seem to be a new promising treatment for cancer.

**Keywords:** apoptosis, *Bcl-2* gene family, cancer, *Colchicum baytopiorum*, *Colchicum umbrosum*, HeLa cells
