Natural Products in Cancer Prevention and Therapy: Current Challenges and Future Directions

Natural products, originating from diverse biological sources, serve as a critical reservoir of bioactive compounds for cancer intervention across prevention, treatment, and supportive care. Their mechanisms extend beyond direct cytotoxicity to include modulation of tumor metabolism-such as glucose, lipid, and glutamine pathways-and the tumor microenvironment (TME), highlighting their multifaceted role in oncology. However, a systematic synthesis of how natural products concurrently target metabolic reprogramming and immune-stromal components across different clinical phases remains lacking. This review delineates the therapeutic applications of natural products-such as flavonoids, alkaloids, and terpenoids-across the clinical continuum, including perioperative support, concurrent chemoradiotherapy, maintenance therapy, and metastasis suppression. We detail their actions in disrupting core metabolic pathways and elucidate their influence on TME components like cancer-associated fibroblasts, extracellular matrix, and immune cells including tumor-associated macrophages and T lymphocytes. Furthermore, we discuss innovative delivery strategies-including nanocarriers and codelivery systems-that enhance bioavailability and enable synergistic combination with chemotherapy or immunotherapy. By integrating mechanistic insights with clinical translation strategies, this work provides a comprehensive framework for employing natural products in biomarker-driven, precision oncology regimens, supporting their evolving role in multimodal cancer care.