Antioxidant capacity of extract from edible flowers of Prunus mume in China and its active components

Prunus mume flowers are used as traditional edible and medicinal materials in China. In this study, phenolic compounds and antioxidant activity of ethanolic extract from flowers of P. mume in China were investigated for the first time. The total phenol content was estimated as gallic acid equivalents by the Folin–Ciocalteu reagent method. The antioxidant activity was measured by DPPH, ABTS+, and OH free radicals scavenging and ferric-reducing antioxidant power (FRAP). Three chlorogenic acid isomers, namely, 3-O-caffeoylquinic, 4-O-caffeoylquinic and 5-O-caffeoylquinic acids, were isolated and purified by preparative HPLC from the ethanolic extract and identified by UV, MS and NMR. The contents of these isolated compounds were quantified by HPLC. Results showed that 5-O-caffeoylquinic acid was of the highest level in these three isomers. The ethanolic extract demonstrated activity to some degree in all the antioxidant assays. In all tested assays, all of the isolated chlorogenic acid isomers exhibited strong antioxidant activities, which were almost the same. The results showed that chlorogenic acid isomers are the key phenolic compounds which are responsible for antioxidant activity of the ethanolic extract from Chinese P. mume flowers.