Antiproliferative Activity Screening in <i>Ocotea</i> spp. Reveals Active Compounds in <i>O. villosa</i> with a Promising Mechanism of Action against Human Breast Cancer Cell Line MCF-7

Breast cancer is a global public health challenge, being the most prevalent cancer and the leading cause of cancer-related mortality among women worldwide. About half of the cases occur without specific risk factors. The biological heterogeneity of the disease, including distinct molecular subtypes, variable aggressiveness, and differential treatment responses, combined with its increasing incidence, makes its management particularly complex. Furthermore, current treatments often cause severe side effects, chronic toxicity, and negatively impact patients' quality of life. Consequently, there is an urgent need for new, safer, and more effective therapies. Natural agents are particularly capable of targeting multiple molecular pathways, which could overcome therapeutic resistance, modulate the tumor microenvironment, and induce fewer and milder adverse effects. Some species of the <i>Ocotea</i> genus have demonstrated encouraging antiproliferative activity. However, the activity against breast cancer of most species of this genus and their active compounds remains poorly investigated. Thus, this study screened 56 <i>Ocotea</i> species extracts for in vitro cytotoxic activity against MCF-7 human breast cancer cells. Among the tested species, only the crude extract of <i>O. villosa</i> leaf (CE) exhibited a significant cytotoxicity against MCF-7 (IC₅₀ = 100.00 ± 6.06 μg/mL; selective index, SI = 1.3). Metabolomic profiling revealed high levels of alkaloids in CE, including chemical annotations of major aporphine compounds (e.g., nuciferine-derived alkaloids). Mechanistic studies indicated that CE has pro-apoptotic activity, inducing apoptosis of 56.59% MCF-7 population, with an activity similar to 5-FU (53.8%), inhibiting cell migration by approximately 5%, and suppressing colony formation by around 50%, without significantly changing the cell cycle. Additionally, semiquantitative RT-PCR evidenced the overexpression of the pro-apoptotic marker CASP9, suggesting intrinsic apoptosis pathway activation by CE. These findings highlight the potential of <i>O. villosa</i> as a source of promising bioactive compounds for the development of anticancer therapies. The complex composition of CE provides various chemical scaffolds as lead compounds, supporting a multitarget mechanism of action with potential in the development of more effective anticancer therapies, reducing therapy resistance and decreasing adverse effects.