Chemical characterization of the anti-inflammatory activity fraction of Epilobium angustifolium

The air-dried aerial part of Epilobium angustifolium is a very popular recreational tea in the Eastern edge of Europe. Studies have found that the extract of E. angustifolium has strong anti-inflammatory effects, and the oenothein B contained therein is speculated the main anti-inflammatory component. In this study, a fraction without oenothein B from the ethanol extract of E. angustifolium exhibited a much stronger anti-inflammatory activity than that of the oenothein B. Guided by rapid characterization of the chemical compositions based on UPLC–Orbitrap–MS/MS, a total of 39 compounds, including 20 flavonoids and 19 other phenolic acids were identified in the active fraction, based on the accurate mass within 3 ppm error. Further investigation resulted in the isolation and identification of 10 compounds, one of which was a new compound, and four known compounds were identified in E. angustifolium for the first time. All isolated compounds exhibited significant inhibitory activity on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 cells. This study indicated that the anti-inflammatory active ingredients in E. angustifolium were mainly concentrated in the 30% ethanol eluted fraction obtained over macroporous adsorption resin. In addition to the oenothein B, there are a large number of other more effective anti-inflammatory components in E. angustifolium .