1046 Asian Pac J Trop Biomed 2017; 7(11): 1046–1054 Contents lists available at ScienceDirect Asian Pacific Journal of Tropical Biomedicine journal homepage: www.elsevier.com/locate/apjtb Review article https://doi.org/10.1016/j.apjtb.2017.10.004 An updated review on pharmacological activities and phytochemical constituents of evening primrose (genus Oenothera) Rebecca Munir1, Nabil Semmar2, Muhammad Farman1*, Naseem Saud Ahmad3 1Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan 2Laboratory of Bioinformatics, Biomathematics and Biostatistics, Pasteur Institute of Tunis, University of Tunis El Manar, Tunisia 3Department of Pharmacology, University of Health Sciences, Lahore, Pakistan ARTICLE INFO ABSTRACT Article history: Genus Oenothera includes medicinal plants that are distributed throughout the world and Received 22 Aug 2017 are known since ancient times. Popular indications of different species of this genus Received in revised form 19 Sep 2017 include treatment of inflammations, diabetes, microbial infections, ulcers, tumors, kidney Accepted 13 Oct 2017 and liver problems. The plants of this genus are a botanical source for various pharma- Available online 23 Oct 2017 ceutically active components like sterols, alkaloids, phenolic acids, flavonoids, triterpe- noids, saponins, biflavonols and tocopherols. This review article is a compilation of chemical composition and biological activities of the various species of the genus Keywords: Oenothera. Oenothera Medicinal plants Chemical composition Biological activities 1. Introduction shaped white, pink, yellow and red flowers, and most are fragrant [2]. Herbal plants play a significant role in the life of humans as The plants owned to Oenothera have a wide range of me- they are being used in different fields such as pharmacology, dicinal properties that prompted us to compile a review article on cosmetics, perfumery, nutraceuticals, beverages and dying in- this particular genus. It comprises all the currently available dustries. Years ago, before the development of synthetic drugs, literature related to the pharmacological activities and phyto- these herbs were mainly used as an alternative therapy to treat chemical constituents of the different species of Oenothera various kinds of diseases. Oenothera, belonging to family including some of the findings of our own research work [3]. Onagraceae, is the second largest genus with 145 species of flowering plants [1]. It mainly occurs in temperate America as 2. Pharmacological activities well as in tropics. The genus is commonly recognized as evening primrose family that consists of herbs and under 2.1. Antioxidant activity shrubs. The plants of this genus occur in the form of annual, biennial or perennial herbs with alternate and mostly narrow Antioxidants play an important role in the preclusion of hu- leaves. The species of Oenothera are known for their saucer- man diseases. Medicinal plant is a rich source of natural radical scavengers and it is believed that this radical scavenging prop- erty is the main causative factor to the therapeutic assistance of many medicinal plants. As far as antioxidant capacity of genus *Corresponding author: Muhammad Farman, Department of Chemistry, Oenothera is concerned, it dates back to the mid of 90s. One of Quaid-i-Azam University, Islamabad 45320, Pakistan. Tel: +92 5190642097 its member Oenothera biennis (O. biennis) L. is the most Fax: +92 5190642241 important medicinal plant. In year 1995, its antioxidant property E-mail: [email protected] (M. Farman). was reported for the first time using lard as the substrate. Peer review under responsibility of Hainan Medical University. The journal implements double-blind peer review practiced by specially invited international Antioxidant power was assessed based on measuring peroxide editorial board members. 2221-1691/Copyright © 2017 Hainan Medical University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). Rebecca Munir et al./Asian Pac J Trop Biomed 2017; 7(11): 1046–1054 1047 number of the sample. Research showed that ethanolic extract of In 2003, a study was conducted on rats to determine the activity O. biennis L. exhibited pronounced antioxidant activity [4,5]. of ethanolic extract from defatted seeds of evening primrose Years later, it was explored that the triterpenoids found in O. biennis L., to control the rise of blood glucose level. It was methanol/water extract of O. biennis also have the potential of found that the extract played an imperative role in the suppression radical scavenging activity [6]. In year 2006, the lipophilic of postprandial hyperglycemia [19]. An investigation on the triterpenoidal esters present in cold-pressed, non-raffinated antidiabetic activity of Oenothera erythrosepala Borb was also evening primrose oil were found to be effective in reducing carried out in the very next year. It was reported that the dose of oxidation stress [7]. The pressing residues from O. biennis were 15 g/100 mL of the oil of Oenothera erythrosepala Borb can also reported to possess a very high antioxidant property [8].In lower the fasting blood glucose in experimental animals [20]. year 2009, methanolic extract of the seeds of O. biennis were Few years later, the anti-hyperglycemic activity of aerial also investigated using DPPH and were found to possess parts (leaves and stems) of O. speciosa Nutt was also investi- significant radical scavenging activity [9]. A research carried gated by conducting an experiment on rats. It was concluded that out in 2010 showed that O. biennis is one of the most 80% aqueous methanolic extract exhibited momentous anti- common botanicals used in anti-aging creams due to its anti- hyperglycemic activities in dose dependant manner [21]. oxidant properties [10]. In the same year, the aerial parts of In year 2015, a study was conducted on some edible plants Oenothera speciosa (O. speciosa) Nutt were also explored for including O. paradoxa to investigate their antidiabetic activity. the determination of their antioxidant potential. It was found Their polyphenolic extracts were screened in terms of a- that 80% methanolic extract of O. speciosa showed potent amylase, a-glucosidase and protein tyrosine phosphatase 1B in vitro antioxidant activity using DPPH radical assay [11]. inhibitors. The study concludes that among these plants Oenothera paradoxa (O. paradoxa) is also an active member O. paradoxa may be considered as a promising natural source of genus Oenothera. An experiment was conducted on three for active compounds with antidiabetic properties [22]. different extracts of defatted seeds of O. paradoxa Hudziok, 60% ethanolic extract, aqueous extract, and 30% isopropanolic 2.3. Anti-inflammatory activity extract, differing by their total content of phenolic compounds and contents of individual polyphenols. It was found that the Complementary and alternative medicine, particularly herbal 60% ethanolic extract exhibited most promising antioxidant therapy, is generally used by the patients with inflammatory activity due to its greater total content of phenolic compounds diseases. In 2004, the anti-inflammatory activity of methanolic and higher content of pentagalloyloglucose [12]. extract of Oenothera rosea (O. rosea) was determined for the In year 2013, another member of this genus O. paradoxa first time by carrageenan-induced rat paw edema model. It was Hudziok was found to protect the skin from any UVA induced found that 70% of the plant extract of O. rosea produced a high damage [13]. reduction of edema [23]. Later on, the aerial parts (leaves and The radical-scavenging capacity of oil seed cake extracts of stems) of O. speciosa Nutt were also reported to possess O. biennis was evaluated against 2,2-azinobis (3-ethylben O. speciosa Nutt significant anti-inflammatory activities in a zothiazoline-6-sulphonic acid). Research showed that the alco- dose dependant manner [21]. holic extract of oil seed cakes exhibited strong antioxidant ca- In the very same year, an ethnopharmacological field survey pacity [14,15]. The antioxidant capacity of the roots of O. biennis was also conducted in the municipality of Tlanchinol Hidalgo, was also evaluated against DPPH and was found to possess high Mexico in which it was further confirmed that O. rosea has the antioxidant potential [16]. potential to cure inflammations [24]. In addition to the In a study conducted in year 2015, in vivo and ex vivo methanolic extract, aqueous extract of O. rosea also possesses properties of emulsions of O. biennis seedcake extracts were strong anti-inflammatory activity. This activity can be attrib- evaluated using the tewameter, pH meter, corneometer, methyl uted to several secondary metabolites present in O. rosea with nicotinate model of micro-inflammation in human skin, and tape no toxic effects at the administrated doses [25]. stripping of the stratum corneum. The studies exhibited that the O. laciniata was also claimed to possess important pharma- emulsions with O. biennis seedcake extracts have strong anti- cological activities. The dichloromethane fraction of O. laciniata inflammatory and antioxidant activity [17]. extract was used to evaluate the anti-inflammatory activity. The By using melan-A cells, in vitro antioxidant and anti- extract effectively inhibited lipopolysaccharide-induced NO, melanogenic effects of methanolic extract of Oenothera laciniata PGE(2), and proinflammatory cytokine production in (O. laciniata)