[Also known as Evening Primrose Oil or Primrose]
Oenothera biennis and other Oenothera species; see GLA 

Origin: The seeds of a native American wildflower, containing 7 to 10 percent gamma-linolenic acid (GLA).

Dosage: Capsules, oil and softgel; generally five 500-mg capsules per day. For rheumatoid arthritis, 540 mg daily to 2.8 g daily in divided doses. Evening primrose oil may take up to six months to work.