# Spectrophotometric Estimation of Polyphenolic Compounds in Willowherbs (Epilobium angustifolium L. and E. hirsutum L.) and Implications for Genetic Resource Conservation

## TL;DR

This study compares the polyphenol content in two willowherb species to identify those with the highest medicinal potential for conservation.

## Contribution

The study provides a comparative spectrophotometric analysis of polyphenolic compounds in two Epilobium species for genetic resource conservation.

## Key findings

- E. angustifolium leaves had 16.8% higher total phenolic content than E. hirsutum.
- E. angustifolium flowers showed 63% higher total flavonoid content compared to E. hirsutum.
- The study identifies populations with high phytochemical potential for conservation.

## Abstract

There is a growing interest in natural bioactive substances, particularly plant-derived secondary metabolites. Polyphenols constitute one of the largest and most significant groups of these metabolites. Rosebay willowherb (Epilobium angustifolium) is well known in traditional medicine and can serve as a reference species for studying its less-known congener, hairy willowherb (E. hirsutum), thereby expanding knowledge of medicinal plants. This study aimed to quantitatively estimate and compare the total phenolic content (TPC) and total flavonoid content (TFC) in the leaves and flowers of Epilobium angustifolium and E. hirsutum, and to identify populations with the highest phytochemical potential. TPC and TFC were quantified using the Folin–Ciocalteu and aluminium chloride (AlCl3) colorimetric assays, respectively, with resulting values regarded as estimates due to the non-specificity of these assays. The results showed that, in terms of TPC, E. angustifolium leaves accumulated 132 ± 3.4 mg_GAE/g (milligrams of gallic acid equivalent per gram of dry plant mass), exceeding those of E. hirsutum by 16.8%; in flowers, the respective values were 153 ± 3 mg_GAE/g, a difference of 1.3%. Regarding TFC, E. angustifolium leaves contained 25 ± 1.4 mg_RE/g (milligrams of rutin equivalent per gram of dry plant mass), which was 20% lower than in E. hirsutum, whereas its flowers accumulated 44 ± 1.4 mg_RE/g, representing a 63% higher content compared with E. hirsutum. The study may contribute to the selection of the Epilobium populations for genetic resource conservation and sustainable utilisation.