Polyphenolic compounds characterization and reactive nitrogen species scavenging capacity of Oenothera paradoxa defatted seed extracts

► We investigated reactive nitrogen species scavenging capacity of different Oenothera paradoxa defatted seeds extracts. ► Characterization of the extracts polyphenols was performed by HPLC-DAD-MS/MS method. ► Extract showed high scavenging capacity against NO and ONOO−. ► Extracts contain five groups of compound: phenolic acids, flavan-3-ol, flavonols and gallotannins. ► Penta-O-galloyl-β-d-glucose a significant NO and ONOO− scavenger may be consider as O. paradoxa extracts quality marker.