Design, Synthesis, and Investigation of Cytotoxic Effects of 5-Hydroxyindole-3-Carboxylic Acid and Ester Derivatives as Potential Anti-breast Cancer Agents

: Breast cancer is a deadly disease with a high prevalence rate among females. Despite several treatments, scientists are still engaged in finding less invasive treatments for this disease. The cellular proliferation rate and cell viability survey are critical to assess the drug’s effect on both normal and malignant cell populations. Indole derivatives are promising candidates for their cytotoxic effect causing on breast cancer cells; however, they are less toxic on normal cells. This study synthesized 23 novel 5-hydroxyindole-3-carboxylic acids and related esters featuring various linear, cyclic, and primary aromatic amines. The MTT assay indicated the cytotoxicity of all acid and ester derivatives against the MCF-7 cells with no significant cytotoxicity on normal human dermal fibroblasts cells. Compound 5d, an ester derivative possessing a 4-methoxy group, was the most potent compound, with a half-maximal effective concentration of 4.7 µM. Compounds 5a, 5d, and 5l bearing ester group in their structure demonstrated cytotoxicity values < 10 µM against the MCF-7 cell line and were safe for advanced screening.