ANTIOXIDANT AND CHEMOPROTECTIVE PROPERTIES OF VERNONIA AMYGALINA DEL. LEAF EXTRACT IN EXPERIMENTAL MODELS OF HEPATOTOXICITY AND HUMAN ERYTHROCYTE LYSIS

Abstract

Reactive oxygen species (ROS) have been implicated in the etiology of several pathological and degenerative diseases. Protective effect of natural products possessing antioxidant properties has played very crucial role in ameliorating deleterious effects produced by ROS. This study investigated the chemoprotective properties of methanolic extract of Vernonia amygdalina (MEVA) in experimental models of hepatic oxidative damage induced by carbon tetrachloride (CCI₄) and 2-acetylaminofluorene (2-AAF) in rats, and tert-butylhydroperoxide (t-BHP)-induced human erythrocyte lysis in vitro. Forty male Wistar strain rats were distributed equally into eight groups. Control groups received normal saline, CCI₄ or 2-AAF alone. Hepatotoxicity was induced in rats with CCI₄ (1.2g/kg/day orally for three weeks) and 2-AAF (100mg/kg/day orally for seven days). MEVA was co-administered with CCI₄ or 2-AAF at 025-0.75g/kg/day. Rats were sacrificed by cervical dislocation and blood collected by cardiac puncture. Liver was excised and homogenised to obtain Post Mitochondrial Fraction (PMF). Activities of Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), y-Glutamyltransferase (yGT), Alkaline phosphatese (ALP) and bilirubin were determined in the serum while cholesterol, phospholipid, triglyccride and in vivo antioxidant activities of Glutathione-S- Transferase (GST), Glutathione Peroxidase (GPx), Catalase (CAT), Superoxide Dismutase (SOD), Glutathione and Malondialdehyde were determined in PMF. Lysis of human erythrocytes was induced with 3mM t-BHP and the inhibitory effect of MEVA determined. In vitro antioxidant activities of MEVA were investigated using Radical Scavenging Activities (RSA) of MEVA on 2, 2-diphenyl-1-picrylhydrazyl (DPPH), Hydroxyl radical (0H), Nitric oxide radical (NO) and Hydrogen peroxide (H₂O₂). Inhibition of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH)-induced Iipid peroxidation and 2.2-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS)-induced radical as well as Reducing Power (RP) by MENA were evaluated. Data were analysed using ANOVA. MEVA decreased of ALT by 6.1%, 26.2%, AST by 3.9%, 35.5%, yGT by 58.1%, 64.7% and malondialdehyde by 6.5% and 57.2% at 0.25 and 0.50g/kg body weight respectively in CCI₄-treated rats. However, increased ALT and AST activities by 14.4% and 91.6% respectively, were in CCI₄ treated rats at 0.75g/kg of MEVA (0.25 and 0.50g/kg) reduced ALT by 34.6%, 24.3%, AST by 18.2%, 39.9% ALP by 56.3%, 57.9%, yGT by 51.6% and bilirubin by 13.8%, 23.2% in 2-AAF-induced hepatotoxicity. While MEVA (0.25 and 0.50g/kg) reduced liver cholesterol by 19.0%, 24.6%, phospholipid and triglyceride were increased by 2.6%, 4.5% and 67.5%, 38.8% respectively. MEVA (0.25 and 0.50g/kg) in 2-AAF treated rats increased activities of GST by 118%, 85.2%, GPx by 28.1%, 39.3%, CAT by 54.5%, 36.4%, SOD by 101.0%, 72.7%, and Glutathione by 44.4%, 40.8%, while Malondialdehyde was reduced by 48.6%, 43.1% respectively. MEVA at 25, 50, 100 and 150ug/ml inhibited t-BHP-induced erythrocyte lysis by 39.3%, 48.4%, 67.3%. and 73.4% respectively. Similarly, MEVA exhibited RSA of 29.6%, 26.4%, 21.8% and 85.8% on DPPH, OH, NO and H₂0₂ respectively. MEVA inhibited AAPH-induced lipid peroxidation by 30.0% and ABTS-induced radical by 1489% with a marked RP of 0.242±0.01. Methanolic extract of Vernonia amygdalina exhibited hepatoprotective activity against CCI₄ and 2-AAF-induced liver damage, and protection against tert-butylhydroperoxide erythrocyte lysis. These protective effects may be due to its antioxidant and free radical scavenging activity.