Gastric ulcer disease is a multi-factorial disease and the significant role played by reactive oxygen species and free radicals  during its pathogenesis is well experimented in both human and experimental animals . The administration of absolute ethanol in the induction of gastric ulcer in experimental rats is one of several methods used in the assessment of the gastro- cytoprotective action of anti-ulcer agents. The injurious effect of absolute ethanol in the stomach as a result of superficial aggressive necrosis due to enhanced lipid peroxidation also involves various mediators like lipoxygenase, cytokines , and excessive generation of oxygen-derived free radicals .
The present study was undertaken to investigate the in-vivo anti-oxidant effect of the root bark extract of C. sieberiana in a model of ethanol-induced gastric ulcer in rats. The results of the present study indicates that oral administration of C. sieberiana root bark extract had a significant and dose-dependent increase of the MUI inhibition (percent) against ethanol-induced gastric lesions (Figure 1). Compared with the untreated ulcer control animals, the inhibition of the gastric ulcers were 27.50%, 50.00% and 85.38% respectively for animals pretreated with 500 mg/kg, 750 mg/kg and 1000 mg/kg body weight of C. sieberiana. This data suggests that C. sieberiana root bark extract possesses strong gastro-cytoprotective properties against ethanol-induced gastric ulcers. This is in agreement with earlier reports that the root bark extract possesses anti-ulcerogenic properties in other induced gastric ulcer animal models  and is supported by the inhibition of decrease of the anti-oxidative enzymes SOD, CAT and GPx.
The endogenous anti-oxidant enzymes SOD, CAT and GPx in the gastric mucus are the key component of cellular defense system against reactive oxygen species. SOD catalyses the dismutation of O2
- to H2O2 which is then scavenged by CAT and GPx. The activity of GPx leads to the elimination of lipid hydroperoxides and hence plays an important role in cell protection . Thus, inhibition of the activities of these enzymes in the gastric mucosa by ethanol may result in the accumulation of hydrogen peroxide with subsequent oxidation of lipids which will ultimately lead to loss of membrane integrity. Results from this study indicate that ethanol administration significantly decreased (p< 0.001) the activities of SOD, CAT and GPx and also serum total anti-oxidant capacity when compared with the un-ulcerated baseline animals. This observation was made 1 h after absolute ethanol administration. A decrease of SOD, CAT and GPx activities in gastric mucosa of rats exposed to ethanol leads to the accumulation of ROS and consequently to an increase in lipid peroxidation concentration and hence an increased mucosal damage as seen from the increase in MUI. These observations confirm the findings of several studies, which reported alterations in anti-oxidant enzyme activities in ethanol exposed animals [18–22]. The dose-dependent inhibition of ethanol-induced decrease in activity levels of gastric SOD, CAT and GPx when the animals where pretreated with C. sieberiana indicates that the root bark extract contains bioactive substances which can stimulate the activity of the endogenous gastric anti-oxidant enzyme system. The induced activity of the antioxidant defence system was supported by an increase in serum total antioxidant capacity, decrease in lipid hydroperoxides (LPO) and inhibition of myeloperoxidase (MPO) activity.
Induced SOD, CAT and GPx activities explains the decrease in LPO from 8.34 ± 0.13 nmol/mg protein in the ulcer control to 3.13 ± 0.13 nmol/mg protein in CS-1000 which is in correlation with the maintenance of baseline (intact) enzyme activity levels of SOD, CAT and GPx (p> 0.05). The gastro-cytoprotective effect of the root bark extract was also accompanied by inhibition of ethanol-induced increase in MPO from 9.20 ± 0.26 μmol/min/mg tissue in the ulcer control to 3.27 ± 0.10 μmol/min/mg tissue in CS-1000. The MPO assay is widely used as an index of neutrophil infiltration in various gastric ulcer models [23–25]. Neutrophils are the major inflammatory cell type infiltrating the injured mucosa following exposure to ethanol  and strategies to counteract the infiltration and/or activation of neutrophils have been shown to protect animals against gastric ulcers . The effect of C. sieberiana in inhibiting an increase of MPO activity may therefore be related to its gastro-cytoprotective ability. This inhibition of neutrophil activation is in agreement with earlier studies that the root bark extract has anti-inflammatory properties [9, 28].
The in-vivo anti-oxidant property of C. sieberiana root bark extract demonstrated in this study may be due to the presence of flavonol/flavonoid/flavone or related compounds with polyhydroxy and/or phenolic groups which we had earlier detected by phytochemical analysis . Further studies we previously conducted  demonstrated that TLC spots revealed by fluorescence under UV light and their reaction with ferric chloride suggest that flavonol/flavonoid/flavone or related compounds with polyhydroxy and/or phenolic groups constituted major chemical substances in the root bark extract. Flavonoids or polyphenolic substances quench ROS, chelate metal ions and regenerate membrane-bound anti-oxidants and it has been demonstrated that substances with anti-oxidant properties, such as polyphenolic compounds, may protect against gastric-damaging effects caused by ethanol [29–35].