Effects of flavonoids on Aβ42 induced cytotoxicity. A. Cells were treated with monomeric Aβ42 (20 μM) for 12 h in the absence or presence of 20 μM of kaempferol-3-O-rhamnoside (K-3-rh), quercitrin (Q), kaempferol-3-O-rutinoside (K-3-ru), gallic acid (GA), protocatechuic acid (PA), gallic acid methyl ester(GAME), quercetin dihydrate(Quer-di-hy), quercetin hydrate (Quer-hy) and kaempferol (K). B. Cells were exposed to monomeric Aβ42 (20 μM) in the presence of 0–50 μM of indicated flavonoids for 12 h. Cell viability was assessed using the MTT reduction assay. Error bars indicate the standard deviation of triplicate independent experiments. Significantly different from control without Aβ42 and with Aβ42 (0 flavonoid concentration) groups indicated as #p < 0.05 or ##p < 0.01 and *p < 0.05 or **p < 0.01, respectively.