Determination and Antioxidant Activity of Flavonoids from Winter Jujube

This study was aimed to analyze the flavonoids from winter jujube and the antioxidant activity was also assessed. Winter Jujube was extracted with 60% ethanol and separated by macroporous resin chromatography to obtain crude flavonoids(FW-1). FW-1 was further purified on silica gel column into FW-2. The composition and chemical structure of FW-1 and FW-2 was analyzed by LC-MS, and their radical scavenging activity against · OH and O 2- · and DPPH radicals was measured. Results showed that total flavonoid contents in FW-1 and FW-2 were 55% and 94%, respectively. The HPLC chromatogram of FW-2 showed that the main peak was E and based on mass spectra, it was identified as bis-flavonoid with a relative molecular weight of 790. Flavonoids at low concentration showed higher radical scavenging capacity against · OH than VC but less effective in scavenging superoxide anion radical than VC. The DPPH radical scavenging rate of flavonoids at 200 μ g/mL was higher than 85%, and the effect was dose-dependent. In conclusion, the main component of the flavonoids extracted from winter jujube was bis-flavonoid and it demonstrated higher antioxidant activity.