Hydrogen peroxide scavenging activity of different amount of CWE, BHA, BHT, quercetin and ascorbic acid 

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... et al., 1997). The reduction capability on the DPPH radical is determined by the decrease in its absorbance at 517 nm induced by antioxidants. The maximum absorption of a stable DPPH radical in ethanol is at 517 nm. The decrease in absorbance of DPPH radical caused by antioxidants is due to the reaction between antioxidant molecules and radical, which results inthe scavenging of the radical by hydrogen donation.The DPPH radical scavenging assay depends on the decoloration of the purple coloured methanolic DPPH solution to yellow by the radical scavengers present in the sample extracts (Blois, 1958). The result of DPPH scavenging activity implies that the plant extract may be useful for treating radical related pathological damages ( Wang et al., 1998). A significant (p<0.01) decrease in the concentration of DPPH radical due to the scavenging ability of the CWE and standards was observed (Fig. 4). The CWE and BHA showed almost equal DPPH scavenging activity, however, significantly are lower than that of quercetin. The scavengingeffect of CWE and standards on the DPPH radical decreasedin the order of quercetin>ascorbic acid >CWE>BHA and were 89, 45, 36 and 31% at the concentration of 60 µg mLG 1 ,respectively. Uncontrolled generation of ROS can lead to their accumulation causing oxidative stress in the cells ( Kunwar and Priyadarsini, 2011). Severe oxidative stress causes cell damage and death (Aruoma, 1998). Superoxide anion radical scavenging activity of 100 µg of CWE, ascorbic acid, BHT and ascorbic acid by the PMS-NADH-NBT method obtained from this study, CWE exhibits free radical scavenging activity as well as a primary antioxidant thatreacts with free radicals, which may hampers the damages caused due to free radical in the human body (Fig. 3). The chelating of ferrous ions by CWE was estimatedwith the method of Dinis et al. (1994). In the presence ofchelating agents, Ferrozine can quantitatively form complexes with Fe 2+ is interrupted and ultimately diminishes the red colour of the complex. The actual mechanism of antioxidant action is chelation of transition metals thus preventing catalysis of hydroperoxidedecoposition and fenton type reactions (Gordon, 1990). Iron can stimulate lipid peroxidation by the Fenton reaction and also accelerates peroxidation by decomposing lipid hydroperoxides into peroxyl and alkoxyl radicals that can themselves abstract hydrogen and perpetuate the chain reaction of lipid peroxidation (Halliwell, 1991). In this assay CWE and standard antioxidant compound interfered with the formation of ferrous and ferrozine complex, suggesting its potent chelating activity which capture ferrous ion before ferrozine. The absorbance of Fe 2+ -ferrozine complex was linearly decreased dose-dependently (from 50-250 µg) (Fig. 5). The difference between CWE and the control was statistically significant (p<0.01). The percentages of metal chelating capacity of 250 µg concentration of CWE, ascorbic acid, BHA and quercetin were found as 84,40, 58 and 34%, respectively. The metal scavenging effect of CWE and standards decreased in the order of CWE>ascorbic acid>quercetine>BHA metal chelating capacity is important since it reduced theconcentration of the catalysing transition metal in lipid peroxidation (Duh et al., 1999). The data obtained from Fig. 5 revealed that CWE demonstrate a marked capacity for iron binding, revealing that their action as peroxidation protector may berelated to its iron binding capacity. Hydrogen peroxide scavenging activity of CWE may be endorsed to their phenolic content, which could bestow electrons to H 2 O 2 , thus counter acting it to water. H 2 O 2 is highly important because of its ability to penetrate biological membranes. H 2 O 2 itself is not very reactive, but it can sometimes be toxic to cell because it may give rise to hydroxyl radical in the cells (Arulmozhi et al., 2008). Scavenging of H 2 O 2 by extracts may be attributed to their phenolics, which can donate electrons to H 2 O 2 , thus neutralizing it to water (Nabavi et al., 2008;Ebrahimzadeh et al., 2009). The ability of CWE to scavenge H 2 O 2 was determined according to the method of Ruch et al. (1989). The scavenging ability of CWE on H 2 O 2 is shown in Fig. 6 and compared with BHA, BHT and ascorbic acid as standards. The CWE was capable of scavenging H 2 O 2 in a dose-dependent. Two hundred and fifty micrograms of CWE exhibited 20% scavenging activity on H 2 O 2 . On the other hand, at the same concentration; BHA, BHT and ascorbic acid showed 32, 80 and 51% activity, respectively. These results indicated thatCWE posses potent H 2 O 2 scavenging activity but had lower than the BHA, BHT and ascorbic acid. However, statistically significant correlation between those valuesand control (p<0.01) was observed. The H 2 O 2 scavenging effect ofsame dose (250 µg) of CWE and standards decreased in the order of BHT>ascorbic ...