Methanol, MeOH/water extracts, infusion, and decoction of Cymbopogon citratus were assessed for free radical scavenging effects measured by the bleaching of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, scavenging of the superoxide anion, and inhibition of the enzyme xanthine oxidase (XO) and lipid peroxidation in human erythrocytes. The extracts presented effect in the DPPH and superoxide anion assay, with values ranging between 40 and 68% and 15-32% at 33 and 50 μg/mL, respectively, inhibited lipid peroxidation in erythrocytes by 19-71% at 500 μg/mL and were inactive toward the XO at 50 μg/mL. Isoorientin, isoscoparin, swertiajaponin, isoorientin 2″-O-rhamnoside, orientin, chlorogenic acid, and caffeic acid were isolated and identified by spectroscopic methods. Isoorientin and orientin presented similar activities toward the DPPH (IC50: 9-10 μM) and inhibited lipid peroxidation by 70% at 100 μg/mL. Caffeic and chlorogenic acid were active superoxide anion scavengers with IC50 values of 68.8 and 54.2 μM, respectively, and a strong effect toward DPPH. Caffeic acid inhibited lipid peroxidation by 85% at 100 μg/mL. © 2005 American Chemical Society.