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

Mitra Mohammadi Bazargani,Mohsen Falahati-Anbaran,Jens Rohloff

doi:10.3389/fpls.2020.595190

Abstract

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.

Highlights

An herbal product is economically affordable when the content of secondary metabolites or the so-called specialized metabolites (Tissier et al, 2014) and its active ingredients has reached a desirable and significant level
In terms of phytochemical properties, 46 compounds were classified into different groups including flavonoids (n = 8), phenolic acids and its derivatives (n = 26), steroids (n = 3), terpenes, lignin and neolignan glycosides (n = 3), and a compound belonging to the group of plant hormones (Table 2)
The average level for secondary metabolites was positively correlated between E. hirsutum and E. parviflorum (n = 46, r = 0.91, P < 0.0001, Figure 3)

Summary

Introduction

An herbal product is economically affordable when the content of secondary metabolites or the so-called specialized metabolites (Tissier et al, 2014) and its active ingredients has reached a desirable and significant level. Both genetic and environmental factors that affect growth and development may alter the biosynthesis of primary and secondary compounds in plants (Moore et al, 2014; Yang et al, 2018). Limited studies have screened the intraspecific variability of secondary metabolites (e.g., FalahatiAnbaran et al, 2018), little is known regarding the interspecific variation in the level of metabolites while comparing multiple populations from a larger geographical range

Methods

Results

Conclusion