Chemical composition and in vitro antioxidant evaluation of commercial water-soluble willow herb (Epilobium angustifolium L.) extracts.

Five commercially available water-soluble extracts prepared from the aerial parts of Epilobium angustifolium L. (Onagraceae) were screened for antioxidant-related properties in a battery of six in vitro assays. Total phenol content and qualitative-quantitative analyses were also carried out. The extracts demonstrated varying degrees of efficacy in each screen. Two extracts, denoted as nonfermented and Tver, were the most effective toward reducing iron(III), scavenging 1,1-diphenyl-2-picrylhydrazyl free radicals, inhibiting hydroxyl radical-catalyzed bovine brain-derived phospholipid degradation, and non-site- and site-specific hydroxyl radical-catalyzed 2-deoxy-D-ribose degradation. The activity profile of the extracts changed, however, when their iron(II) chelating ability was assessed. The nonfermented and Tver extracts were not as effective iron(II) chelators as the extract denoted as Lotos. All the extracts contained Folin-Ciocalteu-reactive substances, which was confirmed by the presence of predominantly polar phenolic analytes (i.e., hydroxylated benzoic acid derivatives and flavonoids).