Abstract:To study the antioxidant capacity of four natural substances，tannin，ginsenoside，Lycium barbarum polysaccharide，and astaxanthin，their free radical scavenging capacity，metal ion chelating capacity，total reduction capacity，and lipid antioxidant capacity were measured.Tannin displayed the strongest DPPH and ABTS+free radical scavenging ability，and its total reduction ability，lipid antioxidant ability，and metal ion chelating capacity were the strongest in the mass concentration range of 0.2 mg/mL-1.0 mg/mL.Ginsenoside displayed the strongest ability to scavenge superoxide free radicals.The scavenging ability of Lycium barbarum polysaccharide for hydroxyl radical was the strongest at a mass concentration range of 0.2 mg/mL-0.8 mg/mL，and the scavenging ability of astaxanthin for DPPH radical was 0.6 mg/mL-1.0 mg/mL，which was higher than that of ginsenoside and Lycium barbarum polysaccharide.Principal component analysis revealed that DPPH and ABTS+free radical scavenging ability，total reduction ability，and metal ion chelating capacity of tannins were better.Prawn cyanin had a better performance on the DPPH radical scavenging ability，ginsenoside had a major impact on the superoxide radical scavenging ability，and Lycium barbarum polysaccharide had a better performance on the hydroxyl radical scavenging ability and total reduction ability.