Impacts of Phenolic Compounds Alone and in Combination with Natural Substances or Drugs on Cancer Cells

Phenolic compounds (PCs) are secondary metabolites found in the root and flower parts of plants that help protect the plant from pathogens. The amount and content of the plant species and the environment in which they live vary. Because PCs have antioxidant properties, they have a preventive effect against oxidising substances. Therefore, PCs in the human diet contribute to the prevention of cancer, osteoporosis, diabetes, and many other diseases. Cancer is the most dangerous and deadly disease among these diseases today. Although many chemotherapeutic drugs are used against cancer, the tendency to use other drugs or other applications has increased because the effectiveness of chemotherapeutic drugs is low and healthy cells are damaged in the process. PCs boost the effectiveness of chemotherapeutic drugs against cancer cells while, preserving the health of other cells. In this review, in vivo and in vitro studies conducted in cancer lines, applications of PCs alone, combined applications of PCs with natural substances, and the effects of PCs with drugs were investigated and discussed. In conclusion, gallic acid, ellagic acid, caffeic acid, and ferulic acid are frequently used in cancer treatment. These findings highlight the potential of PCs as versatile adjuvants in cancer treatment, which can increase drug efficacy, protect healthy cells, and minimise toxicity. Consequently, they highlight the therapeutic potential of PCs as complementary agents in cancer treatment strategies.