Abstract:The preparation conditions of red pigment from Brassica napiformis were optimized by single factor experiment and the resultant red pigment was then purified by AB-8 macroporous adsorption resin.The effects of pH，light，and food additives on the stability of red pigment were studied.The scavenging activity of B.napiformis red pigment against 1，1-diphenyl-2-picrylhydrazyl（DPPH）radicals，2，2'-azino-bis（3-ethylbenzothiazoline-6-sulfonic acid）（ABTS）cation radicals，and hydroxyl radicals，and its protective effects on human HaCaT keratinocytes damaged by medium-wave ultraviolet ray（UVB）were detected to explore its antioxidant activity.The results showed that the optimal temperature was 80 ℃，the optimal heating time was 3 h，and the optimal concentration of ethanol extraction was 80%（volume fraction）.After purification by AB-8 macroporous adsorption resin，the B.napiformis red pigment was obtained with a yield of（3.26±0.014）%.The red pigment remained stable in the acidic environment，and the preservation rate decreased significantly in the slightly acidic environment close to neutral.Illumination at a high temperature significantly reduced the stability of red pigment solution，but slightly affected the red pigment in solid state.Sugar additives and antioxidants had no obvious effect on red pigment.Mg2+，Ca2+，K+，and citric acid had a hyperchromic effect on the pigment，while sodium metabisulfite significantly reduced the preservation rate of the pigment solution.The red pigment showed signifi－cant scavenging abilities against DPPH，ABTS+，and hydroxyl free radicals.It exerted an antioxidant and protective of cell effect by potentiating the activity of superoxide dismutase（SOD）and the content of reduced glutathione（GSH）in UVB-damaged HaCaT cells and reducing the content of malondialdehyde（MDA）.