Antioxidant Activity and Stability of Flavonoids from Mei-tea (Ampelopsis grossedentata)
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Abstract:
In this study, the flavonoids in Mei-tea (Ampelopsis grossedentata) were extracted by the ultrasoundassisted 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.