Advancement of Natural Compounds as Anti-rheumatoid Arthritis Agents: A Focus on Their Mechanism of Actions.

Rheumatoid Arthritis (RA) is a chronic inflammatory disease characterized by infiltration of inflammatory cells, synovial hyperplasia, pannus formation and bone destruction. RA is associated with high incidence of disability worldwide. Although several anti-RA agents are available in the market, clinical use of these drugs is limited due to their severe side effects. Several studies are currently exploring new anti-rheumatic drugs which are more effective and have fewer side effects. Notably, natural products with anti-RA effect have been identified and studies have reported the underlying molecular mechanisms of action of the novel and known compounds. This review explored naturally occurring known and novel compounds that have anti-RA activity. Further, the compounds are classified based on their molecular mechanisms of action as anti-RA agents. In addition, the safety of compounds from natural sources is compared with that of conventional drugs. In addition, clinical trials for anti-RA compounds isolated from natural plant sources were summarized in this manuscript.