Evening Primrose

Background & General Info

Evening primrose, or Oenothera biennis, is widely spread throughout the gardens, roadsides, and meadows of North America. [1] Its oil is universally used in alternative therapy and is noteworthy for its copious amount of omega-6 essential fatty acids, being one of the richest natural products in terms of phytosterol content. [2][3] From its Central American origin, this wild medicinal plant has gone far and currently has become one of the most extensively used herbs worldwide with great economic importance in medicines and nutraceutics. [4] The oil is acquired from evening primrose’s seeds and is typically vended as dietary supplements in capsular forms (gel cap) for various conditions. [5]

Evening Primrose - Botany

Evening primrose is an erect biennial distinguished for its roots that resemble those of turnips; its oblong to lance-shaped, finely toothed leaves with short hanging petioles; and most prominently its solitary, fragrant, yellow flowers that open only in the evening—hence the name of the plant. The plant’s gray or black seeds are contained in long, linear receptacles that look like small, dried okra pod and can be poured once matured. [1]

Evening Primrose - History & Traditional Use

Evening primrose is a valuable medicinal plant for Native Americans, who apply it on bruises. A poultice made from the roots of the plant is recommended for hemorrhoids, whereas its leaves are traditionally used to remedy minor wounds and relieve gastrointestinal complaints and sore throats. [4][5] The Cherokee, the indigenous people of the Southeastern Woodlands, consume the plant as food as a means to lose weight, especially the roots that are said to provide strength. Alternatively, the Potawatomi use the seeds to treat a variety of conditions and similarly spread poultice of the whole evening primrose over bruises. [1]

Evening Primrose - Herbal Uses

Celebrated as a well-known alternative treatment of various systemic diseases characterized by chronic inflammation, including atopic dermatitis and rheumatoid arthritis, evening primrose oil is also regularly used to manage conditions distinct to women such as breast pain, menopausal and premenstrual symptoms, and cervical ripening and can be helpful in inducing labor. [2] It is also traditionally employed as treatment of eczema, asthma, and other breast-related maladies. [4]

Evening Primrose - Constituents / Active Components

Evening primrose contains large quantities of flavonoids, steroids, tannins, fatty acids, and terpenoids, all of which contribute to its important biological activities, including antitumor, anti-arthritic, and anti-inflammatory effects. [6] According to the quantification of Montserrat-de la Paz (2014) through GC–MS and HPLC techniques, oleic (7%), linoleic (74%), and gamma-linolenic (9%) acids appear to be the most abundant fatty acids. β-Sitosterol and campesterol are predominant in phytosterol fraction, whereas tetracosanol and hexacosanol are plentiful in linear aliphatic alcohol fraction. Ferulic acid is the major constituent of the phenolic fraction. [3]

Evening Primrose - Medicinal / Scientific Research


Treatment principally comprising evening primrose oil at a dose of 5 or 10 gm/kg/day for 6 weeks had been shown in the study of Abo-Gresha et al. (2014) to improve the electrocardiographic pattern, serum lipid profile, cardiac biomarkers, and percentage of platelet aggregation in rats experimentally induced to have high levels of cholesterol and myocardial infarction. Furthermore, a reduction of serum levels of tumor necrosis factor-α, interleukin 6, and cyclooxygenase-2 and of tumor necrosis factor-α and transforming growth factor-β in the cardiac homogenate was observed. Histopathological findings indicated also noticeable amelioration. Evening primrose oil had also been found to encourage cardiac recovery in hypercholesterolemic rats with myocardial infarction. [7]


In MTT assay, Singh et al. (2017) investigated the antiproliferative activity of compounds isolated from the roots of evening primrose against selected cancer cell lines. Results from this study revealed the ability of oenotheralanosterol B alone and a mixture of oenotheralanosterols A and B to inhibit the growth of breast, hepatic, prostate, and leukemia cancer cell lines and mouse macrophages, with IC50 values ranging from 8.35 μg/mL to 49.69 μg/mL. Oenotheralanosterols A and B and their mixture also suppressed the activity of ornithine decarboxylase, strongly interacting with this enzyme. Ornithine decarboxylase influences cell growth, proliferation, and transformation and is overexpressed in some types of solid cancers. Aside from oenotheralanosterols A and B, cetoleilyl diglucoside and dihydroxyprenylxanthone had been shown to impede the activity of cathepsin D, a protease associated with cell invasion and apoptosis. [6]


Long-chain fatty alcohols from evening primrose oil had been demonstrated in a 2014 study to display anti-inflammatory activity in vitro, supporting its traditional use to manage conditions presenting inflammation as manifestation. These fatty alcohols, which include hexacosanol (38.65%), tetracosanol (31.59%), docosanol (11.36%), and octocosanol, compose the non-triacylglycerol fraction of evening primrose oil and were demonstrated to significantly prevent the release of phospholipase A2 (an enzyme that hydrolyzes fatty acids) and thromboxane B2 (a platelet-produced vasoconstrictor deemed vital during inflammation and injury). The fraction significantly lowered the production of nitric oxide (a regulatory signaling molecule that mediates aspects of inflammatory responses) in a dose-dependently manner. Furthermore, results from western blot assay indicated a reduction of gene expression of the enzyme cyclooxygenase-2 at all doses of long-chain fatty alcohols, and a marked decrease in the secretion of inflammatory cytokines from lipopolysaccharide-stimulated murine macrophage, namely, interleukin 1β and tumor necrosis factor-α, was observed. [4]


The antimicrobial activity of compounds isolated from evening primrose roots was confirmed by a 2017 study from researchers of the CSIR’s Central Institute of Medicinal and Aromatic Plants, India. As validated by analysis using the disc diffusion and broth dilution methods, evening primrose compounds were effective against selected microbes (bacteria and fungi), with a growth inhibition ranging from 6 to 14 mm and a minimum inhibitory concentration between 125 and 500 μg/mL. In particular, the compounds oenotheralanosterol B and acetylated dihydroxyprenylxanthone displayed superior antimicrobial activity, with a minimum inhibitory concentration of 62.50–500 μg/mL. [6]


Findings from a 2009 study pointed out the substantial anticoagulant and anti-platelet action of evening primrose oil. In this study, evening primrose oil at concentrations of 90, 180, and 360 µL/kg was administered to healthy rabbits for 30 and 60 days. This led to a marked increase in coagulation parameters in all assays, except for fibrinogen time, perhaps because of the inactivation or inhibition of factors that influence coagulation. The administration of evening primrose oil also resulted in a significant decrease in platelet count in experimental rabbits. [8]


A 2005 randomized, double-blind, placebo-controlled study provided findings on the ability of evening primrose oil to enhance biophysical skin parameters, which are essentially signals of changes in skin tissues related to age. Orally administered in soft gel capsules twice a day for 12 weeks, evening primrose oil at a dose of 500 mg was tested on healthy adults to evaluate its effect on skin moisture, transepidermal water loss, redness, firmness, elasticity, fatigue resistance, and roughness. Significant differences among all measured variables except skin redness were observed between the group treated with evening primrose oil and that with placebo at the 12th week, as well as an improvement in skin moisture, transepidermal water loss, elasticity, firmness, fatigue resistance, and roughness by 12.9%, 7.7%, 4.7%, 16.7%, 14.2%, and 21.7%, respectively. [9]

Atopic Dermatitis:

Atopic dermatitis is a chronic, eczematous skin condition marked by itching and inflammation. [10] Evening primrose oil has attracted scientific attention as a possible candidate in the management of atopic dermatitis because of its ample amounts of gamma-linolenic acid. However, there are conflicting results from different researches across the globe regarding the purported benefit an individual with atopic dermatitis can gain from using evening primrose oil. A 2008 randomized placebo-controlled study published in the Indian Journal of Dermatology, Venereology and Leprology evinced the safety and efficacy of evening primrose oil as medicine to manage atopic dermatitis. In this study, 96% of patients clinically diagnosed to have atopic dermatitis displayed improvement following receipt of 500 mg of evening primrose oil in clear unmarked capsules. A significant difference between the outcomes of treated and placebo groups was noted and there was no major adverse event reported during the duration of assessment. [11]

Dental Caries:

A 2011 Japanese study had demonstrated the ability of extract derived from evening primrose seeds to inhibit Streptococcus mutans itself and the dental caries this bacterial species can cause. The extract was shown to stimulate a strong aggregation of Streptococcus mutans MT8148 cells and to cause an approximately 90% decrease in the hydrophobicity of cell surface at a concentration of 0.25 mg/mL. In addition, evening primrose extract reduced the sucrose-dependent adherence of the MT8148 cells, with a reduction rate of 73% perceived at a concentration of 1 mg/mL. In the presence of the extract studied, biofilm development phase was remarkably altered, as revealed through confocal microscopic imaging. Rats consuming 0.05 mg/mL of evening primrose seed extract in drinking water had significantly lower caries scores than those drinking only water that does not contain the extract. [12]

Evening Primrose - Contraindications, Interactions, And Safety

Overall, the use of evening primrose oil is well tolerated, with only few minor adverse effects having been rarely reported, such as gastrointestinal upset and headaches. [2] This is especially true for short periods of time for a majority of patients; however, in the case of long-term use, the safety of evening primrose oil has not yet been confirmed. [5] Because of paucity of data in literature regarding the safety of evening primrose oil during gestation, pregnant women should best avoid it as a cautionary measure. [2] It should be noted that concurrent use of evening primrose oil and warfarin (Coumadin), an anticoagulant drug, may elevate risk of bleeding. [5]


[1] J. Meuninck, Basic Illustrated Medicinal Plants, Guilford, Connecticut: Globe Pequot Press, 2014. https://books.google.com/books?id=DSvVBQAAQBAJ

[2] B. Bayles and R. Usatine, "Evening primrose oil," American Family Physician, vol. 80, no. 12, p. 1405–1408, 2009. https://www.ncbi.nlm.nih.gov/pubmed/20000302

[3] S. Montserrat-de la Paz, "Phytochemical characterization of potential nutraceutical ingredients from Evening Primrose oil (Oenothera biennis L.)," Phytochemistry Letters, vol. 8, p. 158–162, 2014. https://www.sciencedirect.com/science/article/pii/S187439001300147X

[4] S. Montserrat-de la Paz, M. García-Giménez, M. Ángel-Martín, M. Pérez-Camino and A. Fernández Arche, "Long-chain fatty alcohols from evening primrose oil inhibit the inflammatory response in murine peritoneal macrophages," Journal of Ethnopharmacology, vol. 151, no. 1, p. 131–136, 2014. https://www.ncbi.nlm.nih.gov/pubmed/24239848

[5] "Evening Primrose Oil," National Center for Complementary and Integrative Health (NCCIH), 30 November 2016. https://nccih.nih.gov/health/eveningprimrose

[6] S. Singh, V. Dubey, D. Singh, K. Fatima, A. Ahmad and S. Luqman, "Antiproliferative and antimicrobial efficacy of the compounds isolated from the roots of Oenothera biennis L.," Journal of Pharmacy and Pharmacology, 2017. https://onlinelibrary.wiley.com/doi/10.1111/jphp.12753/full

[7] N. M. Abo-Gresha, E. Z. Abel-Aziz and S. M. Greish, "Evening primrose oil ameliorates platelet aggregation and improves cardiac recovery in myocardial-infarct hypercholesterolemic rats," International Journal of Physiology, Pathophysiology and Pharmacology, vol. 6, no. 1, p. 23–36, 2014. https://www.ncbi.nlm.nih.gov/pubmed/24665356

[8] A. Riaz, R. Khan and S. Ahmed, "Assessment of anticoagulant effect of evening primrose oil," Pakistan Journal of Pharmaceutical Sciences, vol. 22, no. 4, p. 355–359, 2009. https://www.ncbi.nlm.nih.gov/pubmed/19783511

[9] R. Muggli, "Systemic evening primrose oil improves the biophysical skin parameters of healthy adults," International Journal of Cosmetic Science, vol. 27, no. 4, p. 243–249, 2005. https://onlinelibrary.wiley.com/doi/10.1111/j.1467-2494.2005.00274.x/abstract

[10] "atopic dermatitis," Merriam-Webster Unabridged. https://unabridged.merriam-webster.com/unabridged/Atopic%20dermatitis

[11] S. Senapati, S. Banerjee and D. Gangopadhyay, "Evening primrose oil is effective in atopic dermatitis: a randomized placebo-controlled trial," Indian Journal of Dermatology, Venereology and Leprology, vol. 74, no. 5, p. 447–452, 2008. https://www.ncbi.nlm.nih.gov/pubmed/19052401

[12] M. Matsumoto-Nakano, K. Nagayama, H. Kitagori and et al., "Inhibitory effects of Oenothera biennis (evening primrose) seed extract on Streptococcus mutans and S. mutans-induced dental caries in rats," Caries Research, vol. 45, no. 1, p. 56–63, 2011. https://www.ncbi.nlm.nih.gov/pubmed/21311187

Article researched and created by Dan Ablir for herbshealthhappiness.com.
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