Abstract: In order to solve the problem that the antioxidant activities of natural extracts are weaker than those of synthetic antioxidants, the effect of zinc ions on the antioxidant activity of lycium extract was explored. The antioxidant activity of ethanol extract from lycium in the presence of zinc chloride, zinc gluconate or zinc acetate was evaluated by lipid oxidation, β-carotene bleaching, DPPH radical scavenging capacity and superoxide anion radical scavenging capacity. Due to different antioxidant mechanisms, the antioxidant activity of ethanol extract from lycium could be affected by zinc ions. The complex between zinc acetate and lycium extract revealed the strongest scavenging capacity against DPPH and superoxide anion free radicals, with a scavenging rate of 85% and 20%, respectively when the complex concentration was 800 mg/L. The complex between zinc gluconate and lycium extract showed the strongest inhibitory effect against lipid oxidation. In contrast, the complex between zinc chloride and lycium extract was the strongest in inhibiting β-carotene oxidation. Different new absorption peaks in UV-visible spectra of these complexes were observed, suggesting that new substances were generated.

Key words: lycium extract, zinc ion, antioxidant activity