Analysis of Functional Components and Antioxidant Activity of Five Kinds of Commercial Curcumin Products

In order to provide reference for the quality evaluation and utilization of curcumin products, the functional components contents and antioxidant activities of different curcumin products were analyzed and compared. The ultra high performance liquid chromatography (UPLC) was utilized to determine the contents of the functional components such as curcumin, demethoxycurcumin and bisdemethoxycurcumin of 5 kinds of commercial curcumin and curcumin extracted (EC) in the lab. Then, the free radical scavenging ability towards DPPH, ABTS, superoxide anion (O₂^-·) , total antioxidant capacity and the inhibitory activity of lipid peroxidation (LPO) were further determined. Finally, the correlation between the content of each functional component and antioxidant activity was analyzed. The results showed that: the total curcumin content in 5 kinds of commercial curcumin was 1.278-2.188 g·hg^-1, while the content of EC was 16.655 g·hg^-1. The median inhibition concentration (IC₅₀) of the commercial curcumin towards DPPH free radical, ABTS free radical and LPO were 749.68-1—568.84 mg·mL^-1, 458.92-851.24mg·mL^-1 and 3.436-6.334 mg·mL^-1, respectively, and the scavenging ability towards O₂^-·was 0-2.956 U·g^-1, and the total antioxidant capacity was 0.082-0.156 mmol·g^-1. By contrast, IC₅₀ of EC towards DPPH free radical, ABTS free radical and LPO were 99.39 μg·mL^-1, 35.49 μg·mL^-1 and 0.296 mg·mL^-1, respectively, and the scavenging ability towards O₂^-· was 20.441 U·g^-1, and the total antioxidant capacity was 1.473 mmol·g^-1. There was a significant positive correlation between the content of curcumin derivatives and antioxidant activities (P<0.01, 0.976≤r≤0.999). The contents of curcumin derivatives and antioxidant activities in the 5 kinds of commercial curcumin products were different from each other, and lower than EC significantly. And the curcumin derivatives were the main contributing constituents for the antioxidant activities of curcumin products.