Current Trends and Prospective Role of Flavonoids and Flavones as Anticancer Agents: A Review

Background: Among the leading causes of death, cancer is second to heart disease as a group of diseases. It has been found that several natural substances, including flavonoids, can treat cancer in addition to several types of chemotherapy. Objective: Flavonoids are naturally occurring polyphenolic compounds with no or minimal toxicity, and have been utilized by people since ancient times. They produce several special therapeutic effects, such as anti-inflammatory, immune response modulating, and antioxidant effects, thereby supporting normal cellular functions. Flavonoids can be classified into six major subtypes or groups based on the degree of oxidation, chemical structure, and unsaturation in the linking chain. Aside from flavonoids and flavanones, flavonols, flavonols, flavones, and anthocyanids also fall into these categories. Methods: In order to find studies on flavonoids as anticancer agents, we searched Science Direct, Google Scholar, PubMed, Wiley Online Library, Springer, and Medline databases. Results: The enhanced generation of reactive oxygen species (ROS) in the electron transport chain due to oxidative stress leads to inflammation, the development of many degenerative diseases, cancer, etc. Oxidative stress can be relieved by flavonoids because they regulate ROS homeostasis (scavenging ROS), trigger apoptosis, and suppress prooxidant enzymes during oxidative stress. Conclusion: Here we review the structure and classification of flavonoids and their mechanisms of action as anticancer agents as well as the challenges involved in developing flavonoids to fight cancer.