In vivo bioactivity assessment on Epilobium species: A particular focus on Epilobium angustifolium and its components on enzymes connected with the healing process

ETHNOPHARMACOLOGICAL RELEVANCE

Epilobium species are generally known as "Yakı Otu" in Turkey, which mens "plaster herb" in English. Young shoots of Epilobium angustifolium L., Epilobium stevenii Boiss., and Epilobium hirsutum L. are consumed as salad or meal. These species have been used as a poultice for the treatment of mouth wounds in traditional medicine. An ointment prepared from leaves is used for skin disorders in children.

AIM OF THE STUDY

We aimed to evaluate the ethnopharmacological use of Epilobium angustifolium, E. stevenii, and E. hirsutum by using in vivo and in vitro experimental models, and to identify the active wound-healer compound(s) and to explain the probable mechanism of the wound-healing activity.

MATERIALS AND METHODS

Evaluation of wound healing effects of plant extracts was performed in rats and mice by linear incision and circular excision wound models. Determination of total phenolic constituents and antioxidant capacities, which are known to promote the wound healing process, were carried out through Folin-Ciocalteau method and 2,2 Diphenyl 1 picrylhydrazyl (DPPH) scavenging assay as well as determination of total antioxidant status (TAS) and total oxidant status (TOS) on the treated tissues. The active ethyl acetate (EtOAc) sub-extract of E. angustifolium was fractionated by different chromatographic separation techniques. The structures of isolated compounds were elucidated via detailed analyzes (NMR and LC/MS). In addition, in vitro collagenase, hyaluronidase, and elastase enzymes inhibitory activity tests were performed on the isolated compounds to discover the activation pathways of the samples.

RESULTS

Among the methanol (MeOH) extracts, E. angustifolium had the highest wound healing activity. Among the sub-extracts, EtOAc showed the highest wound healing activity. Thus, EtOAc sub-extract was subjected to chromatography to isolate the active compounds. Five known flavonoids namely hyperoside (quercetin-3-O-β-D-galactoside) (1), kaempferol (2), kaempferol-3-O-α-L-rhamno pyranoside (3), quercetin-3-O-α-L-rhamno pyranoside (4), and quercetin-3-O-α-L-arabino pyranoside (5) were isolated from the EtOAc sub-extract of E. angustifolium. In vitro tests showed that hyperoside could be the compound responsible for the wound-healing activity by its significant anti-hyaluronidase, anti-collagenase, and antioxidant activities.

CONCLUSION

The EtOAc sub-extract of the aerial part of Epilobium angustifolium displayed remarkable wound-healing activity with anti-hyaluronidase, anti-collagenase, and antioxidant activities. Hyperoside was detected as the primary active compound of the aerial parts. According to the results, we suggest that EtOAc sub-extract of E. angustifolium and hyperoside may be a potent nominee to be used for the improvement of a wound-healing agent.

Comparative Analyses of Phytochemical Variation Within and Between Congeneric Species of Willow Herb, Epilobium hirsutum and E. parviflorum: Contribution of Environmental Factors

The plants in the Epilobium genus are considered to have several important medicinal properties due to their unique chemical composition. Although metabolic profiles of medicinal plants are mainly controlled by genetic factors, their production is also to some degree influenced by environmental factors, thus, variations in the levels of phytochemicals may represent long-term ecological and evolutionary interactions. In order to depict the magnitude of natural variation in level of chemical compounds among conspecific populations of Epilobium hirsutum (n = 31) and E. parviflorum (n = 16), metabolite profiling of aerial parts of plants was performed with gas chromatography/mass spectrometry analysis. Putative identification and structure annotation revealed the presence of 74 compounds including 46 compounds considered secondary metabolites categorized into flavonoids (n = 8), phenolic acids (n = 26), steroids (n = 3), and terpenes (n = 5) across all populations. Although there was a considerable natural variation among conspecific populations, principal component analysis revealed a clear separation of populations of each species based on the second main principal component which was highly correlated with eight secondary metabolites. The level of secondary metabolites was significantly correlated between species (r = 0.91), suggesting shared metabolic pathways underlying the production of chemical compounds. In addition, redundancy and variance partitioning analyses by including bioclimatic variables and altitude revealed a significant contribution of elevation in explaining the total variation of secondary metabolites in E. hirsutum. Two-thirds of all secondary metabolites were significantly correlated with altitude in E. hirsutum. The large-scale geographic analyses of populations revealed additionally detected flavonoids and terpenes (E. hirsutum and E. parviflorum) and steroids (E. hirsutum) for the first time. This study provides significant information on additional chemical compounds found across the distribution range of the two ecologically important species of willow herb and emphasizes the importance of geographic-wide sampling as a valuable strategy to depict intraspecific and interspecific variability in chemical traits.

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.

Phytochemistry, pharmacology and traditional uses of different Epilobium species (Onagraceae): a review

ETHNOPHARMACOLOGICAL RELEVANCE

The Epilobium genus (willowherb) comprises of ca. 200 species of herbaceous plants distributed around the world. Infusions prepared form willowherbs have been traditionally used externally in skin and mucosa infections and in the treatment of benign prostate hyperplasia. Nowadays extracts from different Epilobium species are widely used by patients, however the lack of clinical studies does not allow to fully establish their efficacy. The present review summarizes published data on phytochemistry, ethnopharmacological use and pharmacological studies concerning willowherb species investigated throughout past few decades.

MATERIALS AND METHODS

Literature survey was performed using Scopus, PubMed, Web of Science and Reaxys databases looking for papers and patents focused on chemical composition and bioactivity of Epilobium species. Systematic research in ethnopharmacological literature in digitalized sources of academic libraries was also carried out.

RESULT

The chemical composition of different Epilobium species and their bioactivities are described. The detailed information on constituents isolated and detected by chromatographic methods is given. The studies show that polyphenols are main compounds occurring in Epilobium herb among which flavonoids, phenolic acids and tannins (oenothein B and oenothein A) are dominating constituents. The extracts and some isolated compounds from Epilobium sp. were shown to possess antimicrobial, anti-proliferative, anti-inflammatory, analgesic and antioxidative activities. Because many studies suggest that oenothein B as dominating constituent may be responsible for Epilobium sp. pharmacological effects, its documented bioactivities were also described.

CONCLUSIONS

The pharmacological studies performed on Epilobium justify the traditional use of this species in external and in gastrointestinal inflammations. As far as the treatment of benign prostate hyperplasia (BPH) is considered, in the literature, there are some reports indicating that Epilobium extracts have a beneficial effect for this disorder, but the number of in vitro studies is not sufficient and the in vivo studies are not conclusive or too preliminary to draw a final conclusion about the efficacy of Epilobium preparations. More in vitro, in vivo and clinical studies to confirm this mode of action are strongly needed. Epilobium's extracts have also documented antioxidative and potential anti-inflammatory properties. Oenothein B can be considered as responsible for some of Epilobium pharmacological properties. Because of the lack of clinical data further studies are needed to provide an evidence base for traditional uses of plant materials belonging to the Epilobium genus.

Determination of macrocyclic ellagitannin oenothein B in plant materials by HPLC-DAD-MS: method development and validation

INTRODUCTION

Oenothein B (OeB) is a dimeric macrocyclic ellagitannin occurring mainly in the genus Oenothera. In the literature no validated HPLC method for quantification of this compound has been reported.

OBJECTIVE

To develop and validate an efficient HPLC method for quantification of OeB in plant materials.

METHODOLOGY

Extraction conditions of OeB from plant material were optimised. Then the first validated HPLC method for quantification was developed.

RESULTS

We have shown that ultrasonic-assisted extraction at 40 °C in 15 min using water are the most optimal conditions for OeB extraction. We have quantified OeB in several plant materials belonging to Oenotheraceae family. The lowest amount of OeB was present in Circaea lutetiana herb (27.64 ± 0.26 mg/g) and the highest was quantified in Epilobium hirsutum aerial parts (72.91 ± 1.38 mg/g).

CONCLUSION

The first HPLC method for quantification of OeB in plant materials was developed and validated. We also for the first time optimised the extraction conditions for OeB.

Vegetational variation of phenolic compounds in Epilobium angustifolium

Epilobium angustifolium L. herbs are used in ethnomedicine to treat benign prostate hyperplasia. The aim of the study was to investigate the phenolic contents in distinct E. angustifolium organs during the whole vegetational period from May to October. The plants were obtained from a remote habitat in Estonia and spectrophotometrically analysed for the total polyphenol, tannin, and flavonoid contents. The total polyphenol content was the highest in roots (85 mg g(-1)) and stems (67 mg g(-1)) in July. The total flavonoid content was the highest in leaves (2.36 mg g(-1)) and flowers (2.09 mg g(-1)) and it remained relatively stable during the summer months. The highest tannin content was found in small growing plants in May; in older ones it declined, whereas the absolute yield per plant was greater. In sum, the aerial organs without stems collected in July-August are the best choice to get E. angustifolium plant material with stable high phenolic content.