Phytochemicals in ethanolic extract of Cinnamomum tamala induce cell cycle arrest, DNA damage and apoptosis in human breast cancer cell lines MDA-MB-231 and MCF-7.

Cinnamomum tamala (CT), commonly known as 'Indian bay leaf' in English and 'Tejpatta' in Hindi is a tree belonging to family Lauraceae and is widely used as a culinary condiment with well-known medicinal properties. In the present study, ethanolic extract of dried CT leaves (EECTL) was characterized by HPLC and the antioxidant activity was evaluated using DPPH radical scavenging assay. Anticancer activity of EECTL was evaluated against human breast cancer cell lines MDA-MB-231 and MCF-7 vis-à-vis normal HEK-293 and Vero cells using MTT assay, along with morphological analysis using phase-contrast microscopy. EECTL-induced chromatin condensation and apoptosis were studied using Hoechst and AO/EtBr staining by fluorescence microscopy, as well as by qRT-PCR analysis. Annexin V-FITC/PI double staining for apoptosis detection and cell cycle analysis using PI were performed using flow cytometry. Catechin (Rt = 6.085 min), eugenol (Rt = 7.211 min) and apigenin (Rt = 19.496 min) were identified as the major bioactive components. EECTL was found to induce apoptosis in MDA-MB-231 and MCF-7 cell lines in a dose-dependent manner with IC50 values of 47 and 110 µg/mL, respectively. Interestingly, EECTL did not exhibit any significant effect on normal HEK-293 and Vero cells. The selectivity indices of EECTL with respect to Vero/MDA-MB-231 and HEK-293/MDA-MB-231 were determined as 5.69 and 8.16, respectively, while those for Vero/MCF-7 and HEK-293/MCF-7 were 2.43 and 3.48, respectively. Mechanistically, EECTL caused cell cycle arrest at G0/G1 in MDA-MB-231 and sub-G0 phase in MCF-7 cells, leading to chromatin condensation and apoptosis. DNA damage and fragmentation were confirmed via comet assay. Expression analysis revealed that EECTL upregulated the expression of TP53 in MDA-MB-231 and MCF-7 cells. EECTL was found to have significant antioxidant potential against DPPH radicals, with an IC50 of 150 µg/mL. This study is the first to report anticancer potential and mechanism of action of EECTL against breast cancer MDA-MB-231 cells. EECTL shows potential to serve as an adjunct to the main line of treatment in breast cancer and may be of interest for future preclinical and clinical studies aimed at developing integrative breast cancer treatments.