Vegetational variation of phenolic compounds in Epilobium angustifolium

Harvest time optimization for medicinal and aromatic plant secondary metabolites

Plant secondary metabolites (SMs) play a crucial role in shielding plants from pathogens and environmental stressors. These natural products find widespread applications across various industries, including pharmaceutical, food, cosmetic, and healthcare. However, the quantity and quality of these compounds in plants can be influenced by factors such as genetics, morphology, plant age, and the seasonal and daily variations. The timing of harvest holds particular significance for medicinal and aromatic plants (MAPs) as their active compounds peak at a specific moment during the plant growth cycle. Determining the optimal harvest time is essential to ensure the plants meet their intended cultivation goal. In this review, we analyzed how developmental and external factors impact the qualitative and quantitative effectiveness of SMs in MAPs. We examined recent studies on the effects of environmental and developmental factors on SMs of MAPs, compiling relevant data for analysis. The results of this review demonstrate how these factors influence the quantity and quality of plant SMs, underscoring the importance of determining the optimal harvest time (known as the balsamic time) to maximize the utilization of these compounds. Our findings offer crucial insights into the factors affecting SMs, serving as a tool for quality control in MAPs production. Moreover, this review can be a valuable resource for researchers, farmers, and industrial users aiming to optimize plant growth and harvest timing for maximum yield. Overall, our review provides valuable information for devising effective strategies to produce high-quality MAPs products.

Phenological Variations in the Content of Polyphenols and Triterpenoids in Epilobium angustifolium Herb Originating from Ukraine

The composition of secondary metabolites undergoes significant changes in plants depending on the growth phase and the influence of environmental factors. Therefore, it is important to determine the harvesting time of plant material for the optimum secondary metabolite profile and therapeutic activity of the primary material. The shoots of Epilobium angustifolium are used as a healing tea due to the presence of polyphenolic compounds. The aim of this study was to assess the composition of phenolic compounds and triterpenoid saponins in E. angustifolium leaves and flowers and to estimate the dynamics of their content depending on the flowering phase. Qualitative and quantitative characterisation of polyphenols and triterpenoids in E. angustifolium samples from Ukraine of three flowering phases were performed using the high-performance liquid chromatography photo diode array (HPLC-PDA) method. During the present study, 13 polyphenolic compounds and seven triterpenoids were identified in the plant material. It was noted that the largest content and the best polyphenol profile was in late flowering. The most important polyphenolic compounds in the plant material were chlorogenic acid, hyperoside, isoquercitin, and oenothein B. The triterpenoid profile was at its maximum during mass flowering, with corosolic and ursolic acids being the dominant metabolites. The results of the analysis revealed that the quantity of many of the tested metabolites in the raw material of E. angustifolium is dependent on the plant organ and flowering phase. The largest content of most metabolites in the leaves was in late flowering. In the flowers, the quantity of the metabolites studied was more variable, but decreased during mass flowering and increased significantly again in late flowering. The results show that E. angustifolium raw material is a potential source of oenothein B and triterpenoids.

Antibacterial and Antimycotic Activity of Epilobium angustifolium L. Extracts: A Review

The aim of this work was to provide an overview of available information on the antibacterial and antifungal properties of Epilobium angustifolium extracts. A literature search of Scopus, PubMed/Medline, and Google Scholar for peer-reviewed articles published between January 2000 and June 2023 was undertaken. A total of 23 studies were eligible for inclusion in this review. Significant variation of antimicrobial activity depending on the tested species and strains, type of extract solvent, or plant organs utilized for the extract preparation was found. E. angustifolium extracts were active against both Gram-positive and Gram-negative bacteria and showed antimycotic effects against the fungi of Microsporum canis and Trichophyton tonsurans and the dermatophytes Arthroderma spp. Greater susceptibility of Gram-positive than Gram-negative bacteria to fireweed extracts was found. A strong antibacterial effect was recorded for Staphylococcus aureus, Bacillus cereus, Micrococcus luteus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii including multi-drug resistant strains. E. angustifolium extract might find practical application as an antimicrobial in wound healing, components of cosmetic products for human and animals, or as food preservatives.

In Vitro Human Skin Penetration, Antioxidant and Antimicrobial Activity of Ethanol-Water Extract of Fireweed (Epilobium angustifolium L.)

Epilobium angustifolium L. is applied as an antiseptic agent in the treatment of skin diseases. However, there is a lack of information on human skin penetration of active ingredients with antioxidative potential. It seems crucial because bacterial infections of skin and subcutaneous tissue are common and partly depend on oxidative stress. Therefore, we evaluated in vitro human skin penetration of fireweed ethanol-water extracts (FEEs) by determining antioxidant activity of these extracts before and after penetration study using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and Folin-Ciocalteu methods. Microbiological tests of extracts were done. The qualitative and quantitative evaluation was performed using gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC-UV) methods. The in vitro human skin penetration using the Franz diffusion chamber was assessed. The high antioxidant activity of FEEs was found. Gallic acid (GA), chlorogenic acid (ChA), 3,4-dihydroxybenzoic acid (3,4-DHB), 4-hydroxybenzoic acid (4-HB), and caffeic acid (CA) were identified in the extracts. The antibacterial activities were found against Serratia lutea, S. marcescens, Bacillus subtilis, B. pseudomycoides, and B. thuringiensis and next Enterococcus faecalis, E. faecium, Streptococcus pneumoniae, Pseudomonas aeruginosa, and P. fluorescens strains. In vitro penetration studies showed the penetration of some phenolic acids and their accumulation in the skin. Our results confirm the importance of skin penetration studies to guarantee the efficacy of formulations containing E. angustifolium extracts.

Evaluation of anticholinesterase effect of some Epilobium species and quantification of hyperoside by HPLC

This article presents the evaluation of anticholinesterase effects of aerial parts of Epilobium angustifolium, E. stevenii and E. hirsutum and isolated flavonoids from E. angustifolium, and quantification of the flavonoids by HPLC. Besides, the highest acetylcholinesterase inhibition was seen in the EtOAc sub-extracts of E. angustifolium and E. stevenii (36.51 ± 1.88 and 39.89 ± 3.09%, respectively), whereas EtOAc sub-extract of E. angustifolium had the best butyrylcholinesterase inhibition (62.09 ± 1.98%). Hyperoside showed strong inhibition activity on both enzymes. The active EtOAc sub-extract of E. angustifolium was quantitatively analyzed for their content of hyperoside (quercetin-3-O-β-D-galactoside) by HPLC. The content of hyperoside in EtOAc sub-extract of E. angustifolium was detected as 3.312%. The anatomical structures of the stem, leaf, sepal, petal, anther, and filament of E. angustifolium were investigated. The anatomical properties given in this study provide a description of E. angustifolium.

Application of green-extraction technique to evaluate of antioxidative capacity of wild population of fireweed (Epilobium angustifolium)

Introduction: Fireweed (Epilobium angustifolium (L.) Holub) is a common weed growing on meadows, roadside and agricultural wasteland, creating vast, rapidly spreading fields.

Objective: The aim of the study was to evaluate the antioxidant activity of extracts from fresh fireweed, harvested at three ripening stages.

Methods: Analysis of antioxidative activity was carried out by DPPH, ABTS and FRAP methods. Total polyphenol and total flavonoid content were also determined. Plant material was extracted using ultra-sound-assisted green extraction technique with methanol, ethanol and isopropanol at different concentrations and water.

Results: The highest antioxidant activity evaluated by DPPH, ABTS and FRAP was found for the extracts prepared in 70% ethanol. The highest content of total polyphenols were observed in extracts in 70% ethanol, whereas the highest content of flavonoids extracts in undiluted methanol.

Conclusion: Epilobium angustifolium harvested at fruit ripening stage seems to be a valuable source of antioxidants.

Inventing a herbal tradition: The complex roots of the current popularity of Epilobium angustifolium in Eastern Europe

ETHNOPHARMACOLOGICAL RELEVANCE

Currently various scientific and popular sources provide a wide spectrum of ethnopharmacological information on many plants, yet the sources of that information, as well as the information itself, are often not clear, potentially resulting in the erroneous use of plants among lay people or even in official medicine. Our field studies in seven countries on the Eastern edge of Europe have revealed an unusual increase in the medicinal use of Epilobium angustifolium L., especially in Estonia, where the majority of uses were specifically related to "men's problems". THE AIM OF THE CURRENT WORK IS: to understand the recent and sudden increase in the interest in the use of E. angustifolium in Estonia; to evaluate the extent of documented traditional use of E. angustifolium among sources of knowledge considered traditional; to track different sources describing (or attributed as describing) the benefits of E. angustifolium; and to detect direct and indirect influences of the written sources on the currently documented local uses of E. angustifolium on the Eastern edge of Europe.

MATERIALS AND METHODS

In this study we used a variety of methods: semi-structured interviews with 599 people in 7 countries, historical data analysis and historical ethnopharmacological source analysis. We researched historical and archival sources, and academic and popular literature published on the medicinal use of E. angustifolium in the regions of our field sites as well as internationally, paying close attention to the literature that might have directly or indirectly contributed to the popularity of E. angustifolium at different times in history.

RESULTS

Our results show that the sudden and recent popularity in the medical use of E. angustifolium in Estonia has been caused by local popular authors with academic medical backgrounds, relying simultaneously on "western" and Russian sources. While Russian sources have propagated (partially unpublished) results from the 1930s, "western" sources are scientific insights derived from the popularization of other Epilobium species by Austrian herbalist Maria Treben. The information Treben disseminated could have been originated from a previous peak in popularity of E. angustifolium in USA in the second half of the 19th century, caused in turn by misinterpretation of ancient herbals. The traditional uses of E. angustifolium were related to wounds and skin diseases, fever, pain (headache, sore throat, childbirth), and abdominal-related problems (constipation, stomach ache) and intestinal bleeding. Few more uses were based on the similarity principle. The main theme, however, is the fragmentation of use and its lack of consistency apart from wounds and skin diseases.

CONCLUSIONS

Historical ethnobotanical investigations could help to avoid creating repeating waves of popularity of plants that have already been tried for certain diseases and later abandoned as not fully effective. There is, of course, a chance that E. angustifolium could also finally be proven to be clinically safe and cost-effective for treating benign prostatic hyperplasia, but this has not yet happened despite recent intensive research. Documented traditional use would suggest investigating the dermatological, intestinal anti-hemorrhagic and pain inhibiting properties of this plant, if any.

Fireweed (Epilobium angustifolium L.): botany, phytochemistry and traditional uses. A review

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, immunomodulatory, antioxidant, and also antimicrobial activities. The aim of the present review was to provide the information 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 occupying 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 ellagitannins. 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 ethnobotanical 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.

Inter-population and inter-organ distribution of the main polyphenolic compounds of Epilobium angustifolium

Rosebay willowherb (Epilobium angustifolium) contains large amounts of polyphenolic compounds, including tellimagrandin I-based oligomeric ellagitannins (ETs). The aim of this study was to assess the interpopulational and inter-organ variability of the polyphenol fingerprint of E. angustifolium. Seven ETs, 11 flavonol glycosides and neochlorogenic acid were quantified by UHPLC-DAD-ESI-QqQ-MS in the leaves, flowers and stem parts of plants from 10 populations. Total polyphenol content of leaves and flowers ranged from 150 to 200 mg/g dry wt, of which 90% was constituted by dimeric to heptameric ETs. Flowers contained, on average, 10% more oenothein B (dimeric ET) and 2 times less oenothein A (trimeric ET) than leaves. Tetrameric and pentameric ETs exhibited rather similar levels in leaves and flowers whereas hexameric and heptameric were 3-4 times more abundant in flowers than in leaves. Quercetin-3-O-rhamnoside, myricetin-3-O-rhamnoside and kaempferol-3-O-rhamnoside were specific to flower tissue and were absent from leaves. The inflorescence stem showed the highest content in total polyphenols with an average of 250 mg/g dry wt and contained remarkably large amounts of oenothein B and A. Polyphenol content steadily decreased along the inflorescence stem and reached its lowest level in the vegetative part of the stem. The interpopulational variability of most polyphenols was within a two- to threefold range across the 10 sampled populations. Myricetin-3-O-glucoside and myricetin-3-O-glucuronide, however, showed a more population-specific distribution with concentrations varying from 0 to 2.3 mg/g dry wt. Finally, this study showed that the levels of oenothein B and A in the plant are not interdependent but that their relative abundance is constant within a population.

Therapeutic Potential of Polyphenols from Epilobium Angustifolium (Fireweed)

Epilobium angustifolium is a medicinal plant used around the world in traditional medicine for the treatment of many disorders and ailments. Experimental studies have demonstrated that Epilobium extracts possess a broad range of pharmacological and therapeutic effects, including antioxidant, anti-proliferative, anti-inflammatory, antibacterial, and anti-aging properties. Flavonoids and ellagitannins, such as oenothein B, are among the compounds considered to be the primary biologically active components in Epilobium extracts. In this review, we focus on the biological properties and the potential clinical usefulness of oenothein B, flavonoids, and other polyphenols derived from E. angustifolium. Understanding the biochemical properties and therapeutic effects of polyphenols present in E. angustifolium extracts will benefit further development of therapeutic treatments from this plant. Copyright © 2016 John Wiley & Sons, Ltd.

Content of phenolic compounds in wild populations of Epilobium angustifolium growing at different altitudes

CONTEXT

Flavonoids are regarded as essential ingredients for the anti-inflammatory activity of Epilobium angustifolium L. (Onagraceae). The metabolic profiles of medicinal plants vary aside from genetic determination due to the influence by external factors.

OBJECTIVES

This study evaluates the influence of altitudinal variation on the content of flavonoids in E. angustifolium in two consecutive growing periods.

MATERIALS AND METHODS

Aerial and herbaceous plant materials were collected at three different altitudes (800, 1000, and 1500 m) during two collection periods. Plant samples (11-13 samples per altitude and year) were extracted with methanol using accelerated solvent extraction (ASE). Identification and quantification of the constituents were achieved by chromatographic means of HPLC-PDA and LC-PDA-MS analyses.

RESULTS

Rising concentrations of flavonol 3-O-glycosides could be detected with increasing altitude. The content of the major compound, quercetin 3-O-glucuronide, ranged from 4.4 ± 2.05 (800 m) to 4.9 ± 1.03 (1000 m) and up to 6.6 ± 1.14 mg/g (1500 m). The total amount of flavonol 3-O-glycosides in 73 analyzed samples ranged from 10.7 ± 1.37 up to 17.3 ± 1.99 mg/g.

DISCUSSION

Quercetin-3-O-glucuronide can be considered as a potential marker for the increased production of flavonols in herbal parts of E. angustifolium at higher altitudinal levels.

CONCLUSION

The study confirms that environmental factors at higher altitude result in elevated levels of flavonols in aerial plant tissues of E. angustifolium. Specific factors for influencing the flavonoid content have to be clarified in further studies.