Bioactivity-guided characterization of antioxidant and anti-inflammatory phenolics from edible Oenothera biennis young shoots

Oenothera biennis (evening primrose) young shoots are consumed as edible greens and possess a phenolic-rich composition distinct from the seed oil, yet their bioactive constituents and biological functions remain insufficiently characterized. Here, we evaluated an ethanol extract of young shoots and leaves for antioxidant and anti-inflammatory activities using bioactivity-guided chromatographic fractionation. The extract was separated into ten time-resolved fractions (OB01–OB10) and analyzed using UPLC–PDA–QTOF/MS. Relatively late-eluting fractions increased antioxidant response element-luciferase activity and reduced intracellular ROS levels in HT22 neuronal cells, while suppressing nitric oxide (NO) production in lipopolysaccharide-stimulated BV2 microglial cells. Chemical profiling identified ellagic acid derivatives and quercetin/kaempferol glucuronides as the principal bioactive constituents. Isolated compounds, including 3-methylellagic acid and quercetin 3- O -glucuronide, exhibited antioxidant and NO-modulating activities consistent with those observed in their parent fractions. These findings demonstrate that phenolic constituents enriched in specific chromatographic regions contribute to the biological properties of O. biennis young shoots, providing a biochemical basis for their use as functional food ingredients.