Comprehensive review of Urtica dioica L. (Urticaceae) phytochemistry and anti-inflammatory properties

Herbal medicinal products are widely considered beneficial and gaining importance in preventing and treating several diseases. Urtica dioica L. (UD) is a medicinal plant that has been used as an herbal remedy and dietary supplement for centuries based on traditional experience or random trials without the know-how of phytoconstituents. UD is one of those herbs with a long record of anti-inflammatory activity and several mechanisms of action have been discussed. Plant part, extraction solvent, and phytoconstituents have a determinant effect on both efficacy and therapeutic objective. Current literature mainly elaborates on the antioxidant effect of Urtica species, with the anti-inflammatory role of UD still being a matter of discussion, as in vitro and in vivo studies have only been characterized to such an extent. In order to elaborate on this topic, the present review aims to characterize the anti-inflammatory action of several UD extracts according to in vitro and in vivo results, as well as the possible molecules and respective mechanism responsible for its anti-inflammatory effect on several pathologies. Despite the knowledge gathered so far surrounding the anti-inflammatory activity of UD, further studies are required to characterize the mechanism of action and discriminate between the molecules underlying the beneficial effects of nettle on inflammatory diseases.