DOI: 10.2478/hepo-2018-000 International journal edited by the Institute of Natural Fibres and Medicinal Plants Vol. 65 No. 3 2019 Received: 2019-08-01 DOI: 10.2478/hepo-2019-0018 DOI: 10.2478/hepo-2018-000 Accepted: 2019-09-20 Available online: 2019-09-30 REVIEW PAPER Fireweed (Epilobium angustifolium L.): botany, phytochemistry and traditional uses. A review ARTUR ADAMCZAK1*, MARIOLA DREGER2, KATARZYNA SEIDLER-ŁOŻYKOWSKA1, KAROLINA WIELGUS2 1Department of Botany, Breeding and Agricultural Technology of Medicinal Plants Institute of Natural Fibres and Medicinal Plants Kolejowa 2 62-064 Plewiska, Poland 2Department of Biotechnology Institute of Natural Fibres and Medicinal Plants Wojska Polskiego 71B 60-630 Poznań, Poland *corresponding author: phone: +48 (61) 665-95-50, e-mail: [email protected] Summary Fireweed (Epilobium angustifolium L., Onagraceae) is one of important medicinal plants used especially in the treatment of urogenital disorders, including benign prostatic hyperplasia (BPH) and prostatitis. The therapeutic effects of E. angustifolium extracts comprise antiproliferative, anti-inflammatory, immunomod- ulatory, antioxidant, and also antimicrobial activities. The aim of the present review was to provide the in- formation on the botany, phytochemistry and traditional uses of E. angustifolium. This plant is a widespread circumboreal species of North America and Eurasia, tolerant in terms of habitat conditions, and often oc- cupying man-made open habitats. Phytochemical studies on E. angustifolium resulted in the identification of about 250 different metabolites, including about 170 substances found for the first time in this plant in the last six years (2014–2019). Fireweed has an abundance of polyphenolic compounds, particularly ellagi- tannins. Oenothein B and quercetin-3-O-glucuronide are proposed as markers for the identification and standardization of the plant raw material. E. angustifolium exhibits significant phytochemical variability in relation to the geographical origin, plant part and time of harvest/vegetation phase. Survey of the ethnobo- tanical literature showed that the above-mentioned species has been widely used not only as a medicinal, but also as an edible, honey and decorative plant. Herba Pol 2019; 65(3): 51-63 52 A. Adamczak, M. Dreger, K. Seidler-Łożykowska, K. Wielgus Key words: rosebay willowherb, phytochemical composition and variability, ellagitannins, oenothein B, ethnobotany Słowa kluczowe: wierzbówka kiprzyca, skład i zmienność fitochemiczna, elagotaniny, oenoteina B, etnobotanika INTRODUCTION botanical part, we described taxonomy, synonyms, and also morphology, ploidy, distribution and habi- Nowadays, the consumption of herbal products and tats of fireweed. The phytochemistry included the the popularity of dietary supplements are growing composition of the bioactive substances found in the throughout the world. Nutraceuticals or functional plant raw material, with particular emphasis on the foods are intended to improve the state of health and newly identified metabolites and with the descrip- well-being and to reduce the risk of nutrition-asso- tion of the phytochemical variability of this species. ciated diseases, including cancer prevention. Fire- In turn, the ethnobotanical characteristic aimed to weed (Epilobium angustifolium L.) is an important present the traditional uses of E. angustifolium as a medicinal plant used in the pharmaceutical, food medicinal, edible, honey and decorative plant. and cosmetic industries. It is particularly utilized in the treatment of benign prostatic hyperplasia (BPH) and prostatitis [1]. Today, dietary supple- BOTANY ments or nutraceuticals containing E. angustifolium components are widely available in many countries in the form of tea, capsules, pills, water and alcohol Taxonomy extracts/tonics. Fireweed extracts are also utilized in creams, shampoos and other cosmetic products, Epilobium (Chamerion) angustifolium is classified to especially for acne. the Onagraceae family, which consists of 22 genera E. angustifolium is a rich source of phenolic com- and approximately 650 species. The genus Chamer- pounds, especially hydrolysable tannins (ellagitan- ion (Raf.) Raf. ex Holub (syn. Chamaenerion Ség.) nins), flavonoids, and phenolic acids [2-4]. Medici- with eight species restricted to the northern hemi- nal properties of fireweed extracts have been attrib- sphere (mainly in Eurasia) belongs to the Onagroi- uted to the synergic effect of polyphenols and the deae subfamily and Epilobieae tribe [18]. Relatively presence of the most abundant, compound – oeno- often, it is included in Epilobium L., which is the thein B. This substance shows various pharmacolog- largest genus in the Onagraceae [19-22]. However, ical activities, including anti-androgenic, antiprolif- Chamerion clearly differs from Epilobium in terms erative, anticancer, antioxidant, anti-inflammatory, of flower structure, leaf arrangement and other and immunomodulatory properties [5-10]. Addi- features [18, 23-25]. Molecular data also show that tionally, E. angustifolium exhibits antimicrobial [11- Chamerion is a separate monophyletic group of 15], analgesic [16] as well as photoprotective and plants [26-28]. antiaging [17] activities. Recently, the number of publications concerning the above-mentioned species has increased signifi- Synonyms cantly. Screening of the Scopus database with the keywords of 'Epilobium/Chamerion/Chamaenerion The Plant List [22] provides more than 40 synonyms angustifolium' found 416 document results, includ- of the species described, with three of these being the ing 80 articles published in the years of 2014–2019. most commonly used: Epilobium angustifolium L., A new detailed summary is required not only for Chamerion angustifolium (L.) Holub and Chamae- phytochemistry and pharmacology of E. angustifoli- nerion angustifolium (L.) Scop. According to Holub um, but also in the case of scattered data on fireweed [23], Chamerion should be considered the correct botany and ethnobotany. Latin name of this genus, while Chamaenerion is The aim of the study was to provide an overview an illegitimate name. On the other hand, Sennikov of information available on the botany, phytochem- [25] recently presented arguments for the restora- istry and traditional uses of E. angustifolium. In the tion of the older name Chamaenerion. However, in Fireweed (Epilobium angustifolium L.): botany, phytochemistry and traditional uses. A review 53 this review, the name appearing most frequently in subentire margin, and glabrous abaxial midribs, the references will be used: Epilobium angustifolium. as well as subglabrous stems and usually triporate E. angustifolium is commonly known as fireweed pollen. The polyploid plants of subsp. circumvagum in the United States and rosebay willowherb in Brit- (n=36, 54) are generally luxuriant with taller stems, ain [25]. Other names mentioned include: peren- larger leaves, flowers and pollen. They have leaves nial fireweed, narrow-leaved fireweed, great willow- with petioles 2–7 mm long, a cuneate base, denticu- herb, willow herb, flowering willow, French willow, late margin, glabrous to very pubescent midribs, as etc. [29, 30]. well as strigillose stems, at least in the upper section, while pollen is usually a mixture of triporate and quadriporate grains [36, 37]. Morphology and ploidy Fireweed is an herbaceous perennial with long Distribution and habitats branched rhizomes and fleshy stolons. Green stems, frequently reddish, glabrous below and pubescent E. angustifolium is a widespread circumboreal spe- above, are erect up to 2 m high. The willow-like cies occurring in the temperate zone of North Amer- leaves are alternate, 3–20 cm long. E. angustifolium ica and Eurasia at a latitude from 25o to 70o north. It blooms from June to September, developing large grows both in the lowlands and in the mountains: in raceme inflorescences consist of a number of pink Switzerland to 2530 m, in North America to 3960 m, (rarely white) flowers (figure 1). They are up to 3 cm and in the Himalayas to an altitude of 4850 m a.s.l. in diameter, zygomorphic, epigynous with a small Diploid populations occur in colder climates: in nectar-secreting disc, markedly protandrous. The Greenland, Canada, Alaska, Siberia and northern capsules, 4–8 cm long, contain small light brown Europe, and also tend to develop at higher altitudes. seeds (1.0–1.3 mm in length) with greyish white Tetraploids grow in warmer and drier habitats oc- hairs up to 13 mm long. One plant could produce cupying the southern part of the range in Eurasia 76 000 wind-dispersed seeds per year [31-33]. The and North America [18, 38, 39]. In turn, triploids weight of 1 000 seeds is about 0.07 g [34] and with- (n=27) appear in mixed-ploidy populations of bor- out the pappus reaches about 0.05 g [35]. der areas [40]. The hexaploid cytotype was reported E. angustifolium is a variable species diverse in only in central Japan and the Yunnan province of terms of morphology and ploidy. The diploid rep- China [36, 41]. resenting subsp. angustifolium (n=18) has sub- Fireweed is a common plant occupying man- sessile leaves with an obtuse or subrounded base, made open habitats, such as deforested or burned Figure 1 Epilobium angustifolium in the blooming phase (Krajewice, Poland) Vol. 65 No. 3 2019 54 A. Adamczak, M. Dreger, K. Seidler-Łożykowska, K. Wielgus areas, roadsides and railway embankments. This Hydrolysable tannins species also occurs on the edge of forests and thick- ets, along streams, on rocky