Background: Cymbopogon citratus, Stapf (CCS) is commonly known as lemon grass. Previous studies showed that it has a strong antioxidant property and have been traditionally used as analgesic, antipyretic, antiseptic in Southeast Asia. However, the effect of CCS on antioxidant defense system has not been demonstrated.
Objective: The present study was conducted to investigate the effects of CCS water extract on rat antioxidant defense system, especially on the expression of γ-glutamylcysteine ligase (γ-GCL) and heme oxygenase-1 (HO-1).
Material and Method: The CCS water extract was screened for its phytochemical contents and antioxidant activity in vitro. Moreover, the extract was studied in rats to evaluate its effects in vivo. Male Sprague-Dawley rats aged eight weeks (250+20 g) were orally administered with CCS at 250, 500 and 1,000 mg/kg/day for one month.
Results: The extract contained flavonoids (496.17 mg gallic acid/g CCS extract) and phenolic compounds (4,020.18 mg
catechin/g CCS extract). The scavenging activity (DPPH assay) of the extract was demonstrated by EC50 of 917.76+86.89 μg/ml whereas the EC50 of the potent antioxidant, vitamin C was 31.22+1.84 μg/ml. In the animals, the protein expression of antioxidant enzymes, γ-GCL and HO-1 was significantly increased in the high dose-treated animals (1,000 mg/kg/day). This was consistent with elevation of serum total antioxidant capacity.
Conclusion: Taken together, the present study provides evidence that CCS water extract exhibits antioxidant activity and antioxidant enzymes induction in vivo.

Keywords: Cymbopogon citratus Stapf, Antioxidant, γ-glutamylcysteine ligase, Heme oxygenase-1