Rheumatoid arthritis (RA) is a chronic, systemic, joint-invading, autoimmune inflammatory disease, which causes joint cartilage breakdown and bone damage, resulting in functional impairment and deformation of the joints. The percentage of RA patients has been rising and RA represents a substantial burden for patients around the world. Despite the development of many RA therapies, because of the side effects and low effectiveness of conventional drugs, patients still need and researchers are seeking new therapeutic alternatives. Polyphenols extracted from natural products are effective on several inflammatory diseases, including RA. In this review polyphenols are classified into four types: flavonoids, phenolic acids, stilbenes and others, among which mainly flavonoids are discussed. Researchers have reported that anti-RA efficacies of polyphenols are based mainly on three mechanisms: their anti-inflammatory, antioxidant and apoptotic properties. The main RA factors modified by polyphenols are mitogen-activated protein kinase (MAPK), interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), nuclear factor κ light chain enhancer of activated B cells (NF-κB) and c-Jun N-terminal kinases (JNK). Polyphenols could be potent alternative RA therapies and sources for novel drugs for RA by affecting its key mechanisms.
Keywords: flavonoids; natural products; phenolic acid; polyphenol; rheumatoid arthritis; stilbene.