Comprehensive identification of minor components and bioassay-guided isolation of an unusual antioxidant from Azolla imbricata using ultra-high performance liquid chromatography—quadrupole time-of-flight mass spectrometry combined with multicomponent knockout and bioactivity evaluation

Azolla imbricata (Roxb.) Nakai is used as a traditional Chinese medicine. However, very limited information is available on its effective components. Traditional procedures for discovering natural bioactive compounds, especially for minor ones, are usually time-consuming and labor-intensive. Therefore, an efficient approach using ultra-high performance liquid chromatography–quadrupole time-of-flight tandem mass spectrometry (UHPLC–QTOF–MS/MS)...