Immunomodulatory Effects of Flavonoids in the Prophylaxis and Treatment of Inflammatory Bowel Diseases: A Comprehensive Review

Inflammatory Bowel Diseases (IBD) comprised of two disorders of idiopathic chronic intestinal inflammation that affect about three million people worldwide: Crohn's disease and ulcerative colitis. Nowadays, the first-line of treatment for patients with mild to moderate symptoms of IBD is comprised of corticosteroids, immunosuppressants, antibiotics, and biological agents. Unfortunately, none of these drugs are curative, and their long-term use may cause severe side effects and complications. Almost 40% of IBD patients use alternative therapies to complement the conventional one, and flavonoids are gaining attention for this purpose. The biological properties of flavonoids are well documented and their antioxidant and anti-inflammatory activities have been arousing attention in the scientific community. Flavonoids are the most widely distributed polyphenols in plants and fruits, making part of the human diet. Taking into account that all ingested flavonoids are expected to exert biological actions at the gastrointestinal level, research on the modulatory effect of these compounds in IBD is of paramount importance. This review intends to summarize, in an integrated and comprehensive form, the effect of flavonoids, both in vitro and in vivo, in the different phases of the characteristic IBD inflammatory network.