Oenothera biennis, commonly known as evening primrose, sun drop, King’s cure-all, and fever plant, is a biennial edible plant widely found in temperate and subtropical regions. Roots, flowers, leaves, and seeds are used in cooking; among them, seeds are the most commonly used part of evening primrose. The oil obtained from the seeds is used as a dietary supplement due to its high content of polyunsaturated fatty acids. The mature seeds contain approximately 7-10% γ-linolenic acid, one of the essential fatty acids, which has been reported to have beneficial effects on rheumatic and arthritic conditions, atopic dermatitis, premenstrual and menopausal syndrome, and diabetic neuropathy.

The polyphenols found in seed extract of evening primrose showed anti-oxidant activities, and long-chain fatty alcohols extracted from evening primrose oil inhibited the inflammatory response in macrophages. Evening primrose oil also has the potential anti-obesity agent as the body and liver weights were reduced when evening primrose oil was administered to cholesterol-fed rats.