Variation in antioxidant properties and metabolites during flower maturation of Flos Lonicerae Japonicae flowers

Antioxidant properties of methanol extracts from Flos Lonicerae Japonicae (FLJ) flowers during maturation were determined with different antioxidant assays, including antioxidant activity in emulsion system, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, superoxide anion radical scavenging and reducing power. Antioxidant metabolites, such as chlorogenic acid, caffeic acid, rutin, 3,5-O-dicaffeoylquinic acid (3,5-O-diCQA) and 3,4-O-diCQA, were also identified and analyzed by DPPH-HPLC-DAD-TOF/MS method. Significant variation in antioxidant properties and related compounds was observed between different maturity stages, and the strongest antioxidant activity was observed at stage I accompanying the highest content of antioxidant compounds. Chlorogenic acid and its derivatives were the main antioxidant compounds in FLJ flowers, accounting for more than 90 % of total bioactive molecules. In summary, bud-developing-stage (stage I and stage II) FLJ flowers possess the highest functional benefit.