Diarylheptanoids with free radical scavenging and hepatoprotective activity in vitro from Curcuma longa

Assay-guided fractionation of the EtOAc soluble fraction of the rhizomes of Curcuma longa furnished three DPPH free radical scavenging diarylheptanoids, curcumin (1), demethoxy-curcumin (2), and bisdemethoxycurcumin (3). Compounds 1-3 showed the DPPH radical scavenging effects with IC50 values of 2.8, 39.2, 308.7 muM, respectively. L-Ascorbic acid and resveratrol as positive controls exhibited IC50 values of 22.5 and 25.0 muM, respectively. Compounds 1-3 showed significant hepatoprotective effects on tacrine-induced cytotoxicity in human liver-derived Hep G2 cells. The EC50 values of 1-3 are 86.9, 70.7, and 50.2 muM, respectively. Silybin (EC50 = 69.0 muM) and silychristin (EC50 = 82.7 muM) were used as positive controls.