In this paper, spectrophotometric method was employed to determine the ability of curcumin to scavenge 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, and the oxidative hemolysis of erythrocytes induced by 2, 2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was used to investigate the inhibitory effect of curcumin on AAPH-induced damage to human erythrocytes. The effect of curcumin on the viability of A375 malignant melanoma cells was measured by MTT assay, and the population of the apoptotic cells was detected by a flow cytometer. The effect of curcumin on the expression levels phosphorylated JNK and Akt was analyzed via Western blot assay. These results showed that curcumin exhibited strong scavenging effects on ABTS and DPPH free radicals in a dose- and time-dependent manner. Meanwhile, curcumin also effectively inhibited the AAPH-induced hemolysis of erythrocytes. The hemolysis inhibition rate of curcumin increased to 52.78 ± 1.03% at a concentration of 40 μM. The MTT assay showed that an increasing concentration of curcumin decreased the viability of A375 cells gradually. The cell viability after treatment with curcumin (40 μM) was only 21.50 ± 1.60%. Further flow cytometric studies showed that the SubG1 peak (apoptotic cells) increased in response to increasing curcumin concentrations. The SubG1 peak (apoptotic cells) reached 63.30% when the curcumin concentration was 40 μM. Further studies by Western blot assay demonstrated that the curcumin-induced apoptosis in A375 cells was related to upregulation of JNK phosphorylation and downregulation of Akt phosphorylation.
