The bioassay-guided fractionation of the MeOH extract of Galla Rhois furnished two hepatoprotective compounds, an equilibrium mixture of 3-galloyl-gallic acid and 4-galloyl-gallic acid isomers (3), 1,2,3,4,6-penta- O -galloyl-β- D -glucose (4), and two inactive phenolic compounds, gallic acid methyl ester (1) and gallic acid (2). Compounds 3 and 4 showed significant hepatoprotective effects with EC₅₀ values of 70.39±5.4 and 29.51±0.7 μ M , respectively, against tacrine-induced cytotoxicity, and 150.9±6.4 and 23.81±0.5 μ M , respectively, against nitrofurantoin-induced cytotoxicity in Hep G2 cells.