The major chemical component thought to be responsible for the anti-inflammatory activity of devil's claw is harpagoside, a monoterpene glucoside. Other iridoid glycosides include procumbide, harpagide, 8-para-coumaroyl-harpagide, and verbascoside. Harpagoside is found primarily in the roots; secondary tubers contain twice as much glucoside as the primary roots. Flowers, stems, and ripe fruits are essentially devoid of the compound, while traces have been isolated from the leaves. Harpagoside can be progressively hydrolyzed to harpagid and harpagogenin. Commercial sources of devil's claw extract contain 1.4% to 2% of harpagoside. Other constituents include carbohydrates, flavonoids (kaempferol, luteolin), aromatic acids, phytosterols, and triterpenes. High-performance liquid chromatography methods for identification have been reported.
