PROTECTIVE EFFECTS OF METHANOL EXTRACT OF Allium cepa ON CYANIDE-INDUCED TOXICITY IN WISTAR RATS

Abstract

Cyanide inhibits cellular cytochrome C oxidase, promotes reactive oxygen species production and causes organ damage. The possible ameliorative effects of Methanol Extract of the Bulb of Allium cepa (MEAC) on cyanide intake was investigated in male Wistar rats. Adult Wistar rats (150-180g) were divided into five groups of six rats each orally given corn oil (control), KCN, KCN+MEAC, KCN+sodium thiosulphate (Na2S2O3) and KCN+quercetin. Animals were sacrificed and blood creatinine (BC), urea (BU), Aspartate Amino Transferase (AST), Alanine Amino Transferase (ALT), Gamma Glutamyl Transferase (GGT), Lactate Dehydrogenase (LDH), Liver Rhodanese (LR) and Brain Lactate Dehydrogenase (BLDH) were determined by spectrophotometry. Superoxide Dismutase (SOD), catalase, Glutathione-S-Transferase (GST), glutathione and malondialdehyde levels were evaluated by spectophotometry and fluorometry. Histological changes were assessed by light microscopy. Pure compounds in MEAC were obtained using column chromatography and subjected to 1H and 13C nuclear magnetic resonance. Data were analysed using Student’s t-test at p=0.05. A dose of 7mg/kg KCN significantly increased the levels of serum ALT (48.2±0.4), AST (82.2±2.2), GGT (46.7±1.4), LDH (1816.6±134.6), BLDH (130.2±6.7) IU/L; BU (8.8±0.6 mmol/L), BC (101.4±6.8 μmol/L), LR (2.1±0.03 mmol/min/mg) relative to control (ALT- 23.1±0.5, AST-34.9±6.8, GGT- 11.6±0.4, LDH- 736.7±96.6, BLDH- 29.1±0.4 IU/L; BU- 4.6±0.4 mmol/L, BC-73.2±3.4 μmol/L and LR- 1.3±0.1 mmol/min/mg). Treatment of KCN-intoxicated rats with MEAC significantly reduced the levels of (ALT-28.5±0.8, AST-44.1±4.0, GGT-14.4±0.3, LDH-1108.0±101.7, BLDH-78.2±1.1 IU/L; BU-7.2±0.2 mmol/L; BC-71.3±5.0 μmol/L) relative to KCN-treated group. Similarly, [KCN+Na2S2O3]-treated rats had lower values of ALT, AST, GGT, LDH, BLDH, BC but a higher value of LR when compared to KCN-treated rats. KCN-intoxication significantly increased malondialdehyde levels in the liver, kidney and brain by 203%, 198% and 126% respectively, relative to the control. However, treatment with MEAC caused significant decrease in malondialdehyde levels in the liver, kidney and brain relative to KCN-treated group. Likewise, malondialdehyde levels in the liver, kidney and brain of [KCN +quercetin]-treated rats and [KCN+Na2S2O3]-treated xxi rats were significantly decreased relative to KCN-treated group. In the control group, liver, kidney and brain SOD levels were 3.5±0.3, 3.9±0.1, 3.8±0.1 U/mg, glutathione levels were 7.2±0.5, 6.8±0.5, 4.2±0.4 μg/g, catalase levels were 0.2±0.03, 0.1±0.001, 0.04±0.002 katf, respectively. These indices were significantly decreased in rats intoxicated with KCN (SOD-2.2±0.1, 2.4±0.1, 2.6±0.2 U/mg; glutathione - 3.0±0.1, 4.8±0.3, 3.8±0.5 μg/g; catalase - 0.07±0.001, 0.01±0.001, 0.02±0.002 katf). Furthermore, KCN-intoxicated rats treated with MEAC, quercetin and Na2S2O3 had significantly increased levels of SOD, glutathione and catalase. Histopathological findings revealed that cyanide-intoxication caused damages in the liver, kidney and brain while treatment with MEAC, quercetin and Na2S2O3 reduced the adverse effect of cyanide. The structure of purified S-compound from Allium cepa was shown as 2-[(Z)-6-(2,3-di-α-D-glucopyranose-4-mercaptophenyl)-4-methyl-5-hexenyl]propanedial. Methanol extract of Allium cepa protected against cyanide toxicity in rats liver, kidney and brain via antioxidative mechanism and enhancement of rhodanese activity. The purified sulphur-compound in Allium cepa may be responsible for the observed activity.