Antioxidant activity from Curcuma spp.

Abstract

In the course of screening for antioxidant activity from plants in Zingiberaceae family, the dichloromethane and ethyl acetate crude extracts from Curcuma spp. (Waan Ma Lueang) were found to have a promising activity, as guided by scavenging effect on the stable radical, 2,2-diphenyl-1 -picrylhydrazyl (DPPH). These crude extracts were separated and led to the isolation of five compounds, namely, curcumin (1), demethoxycurcumin (2), and bisdemethoxy curcumin (3), ar-turmerone (4), and 1-hydroxy-1,2-di-(6-methyl-3-isopropenyl-2-propionyloxy-1-cyclohexene)-1-propene (5). The structures of all compounds were elucidated on the basis of spectroscopic methods, as well as comparison with literature data. In terms of antioxidant activity, the isolated compounds were evaluated by various in vitro model assays, which include the DPPH radical scavenging activity, xanthine oxidase-related activity (superoxide scavenging activity and inhibitory effect on xanthine oxidase), and lipid peroxidation inhibitory activity, by comparison with BHA and allopurinol. The free radical scavenging activity on DPPH indicated that compounds 1, 2, 4, and 5 exhibited significant activity with IC50 = 0.16, 0.27, 0.17, and 0.19 mM, respectively, while compound 3 gave the weakest activity (IC50 = >0.50 mM). Their superoxide scavenging activity was in order of compound 1 (IC50 =0.31 mM), 2 (IC50 =0.33 mM), 4 (IC50 =0.34 mM), 3 (IC50 =0.35 mM), 5 (IC50 =0.36 mM). Furthermore, all compounds displayed highly inhibitory activity against xanthine oxidase and lipid peroxidation, particularly compound 1 (IC50= 0.30 and 0.19 mM), followed by compound 4 (IC50= 0.30 and 0.21 mM), 2 (IC50 = 0.31 and 0.22 mM), 5 (1C50 = 0.31 and 0.24 mM), and 3 (IC50 = 0.42 and 0.27 mM), respectively.