In this study,the flavonoids in Mei-tea(Ampelopsis grossedentata)were extracted by the ultrasound-assisted water extraction method,and the antioxidant activity of flavonoids in the aqueous extract of Mei-tea(Ampelopsis grossedentata)was investigated by the DPPH and ABTS radical scavenging assays,and the effects of different lighting,pH values,metal ions,oxidants,reducing agents and water-soluble macromolecules on the stability of flavonoids in the aqueous extract of Mei-tea(Ampelopsis grossedentata)were investigated by UV spectrophotometry.The results showed that the flavonoids had good antioxidant activity and could scavenge effectively DPPH and ABTS+free radicals,with the IC50 values being 3.09 μg/mL and 1.43 μg/mL for DPPH and ABTS+radicals,respectively.Meanwhile,the flavonoids in the Mei-tea(Ampelopsis grossedentata)underwent autoxidization during a long-term storage and light could promote the oxidation of the flavonoids in Mei-tea(Ampelopsis grossedentata)to a certain extent.Alkaline conditions and reducing agents could destroy the molecular structures of the flavonoids in the Mei-tea(Ampelopsis grossedentata).The flavonoids in the Mei-tea(Ampelopsis grossedentata)could easily form insoluble complexes with metal ions such as Cu2+and Fe3+,thereby affecting the stability of flavonoids.Water-soluble macromolecules could protect the flavonoids in the Mei-tea(Ampelopsis grossedentata)to a certain extent,to prevent their oxidation through avoiding contact with oxygen.
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