Antioxidant Activities and Chemical Constituents of Flavonoids from the Flower of Paeonia ostii

Paeonia ostiiis a traditional medicinal plant popularly used in China. This study intended to evaluate the antioxidant properties and the chemical components of the flavonoid-rich extracts from the flowers ofP. ostii. The results showed that the flavonoid-rich extracts from the flowers ofP. ostiihad strong scavenging capacities on 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), hydroxyls, superoxide anions, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in a dose-dependent manner. Five flavonoids, dihydrokaempferol (1), apigenin-7-O-β-d-glucoside (2), apigenin-7-O-β-d-neohesperidoside (3), kaempferol-7-O-β-d-glucopyranoside (4), and kaempferol-3-O-β-d-glucopyranosyl-7-O-β-d-glucopyranoside (5), were isolated from the flavonoid-rich extracts of the flowers ofP. ostii. High-performance liquid chromatography (HPLC) analysis revealed that compounds3and4were abundant in theP. ostiiflower and in flavonoid-rich extracts. The main components of the flower ofP. ostiiare flavonoids. The high antioxidant activity of the flavonoid-rich extracts may be attributed to the high content of flavonoids. The five isolated flavonoids were the primary antioxidant ingredients, and may play important roles in the strong antioxidant activities of this flower. Based on the obtained results, the flower ofP. ostiicould be a potential source of natural antioxidants in food and pharmaceutical applications.Keywords:flavonoids of peony flower;Paeonia ostii;natural antioxidant;chemical constituents