Metal-Free, Visible-Light-Mediated Synthesis of Tetracyclic Benzimidazole: Regioselective C–H Functionalization with In Vitro and Computational Study of Anti-breast Cancer Compounds

Globally, breast cancer is the leading cause of mortality. Within the field of antibreast cancer drug design by several compound docking studies, eight new N-containing nonsteroid tetracyclic derivatives have been synthesized via regioselective intramolecular C-H functionalization by visible light. The adopted methodology is highly efficient, green, and sustainable to unload a new pathway with excellent yield. It offers a rapid, low-cost, catalyst-free method for creating physiologically active molecules from easily accessible substrates. The synthesized substances were described using spectroscopic methods like HRMS, ¹HNMR, ¹³CNMR, and XRD analysis. This study explores the cytotoxic potential of novel compounds against human MCF-7 breast cancer cells. This study includes in vitro experiments to assess the effect of our compounds on cells. These experiments include cytotoxicity assessment by cell cycle, apoptosis, MTT test analysis by flow cytometry, reactive oxygen species (ROS) production assessment, etc. Among the novel compounds, compound <b>2e</b> exhibited the most potent cytotoxic activity, with an inhibitory concentration (IC₅₀) of 40 nM, surpassing the efficacy of established drugs such as exemestane (IC₅₀ 24.97 micromolar) and tamoxifen (IC₅₀ 5.45 μM). Compound <b>2e</b> also significantly induced apoptosis and cell cycle arrest in the G1 phase, increasing the apoptotic cell population to 65.97%. Additionally, the compound led to a marked rise in the level of ROS generation, implicating oxidative stress in its mechanism of action. Molecular docking and dynamic simulation further supported the vigorous anticancer activity of compound <b>2e</b>, demonstrating its promise as an effective breast cancer treatment.