Assessment of hepatoprotective effect of extracts of Alstonia boonei leaf in isoniazid and rifampicin co-treated rats

Anti-tuberculosis drugs, rifampicin and isoniazid, in their mode of action can generate toxic reactive metabolites upon oxidative bio-activation of the parent compound by the cytochrome P₄₅₀ monooxygenase system leading to liver injury. Currently, there is increased awareness of the benefits in the use of medicinal plants in the management of various oxidative stress-related diseases. This study therefore evaluated the hepatoprotective effect of aqueous and ethanol extracts of Alstonia boonei leaf in rats co-treated with isoniazid (INH) and rifampicin (RIF). Sets of albino Wistar rats were placed into eight groups. The animals in each group (except the normal control) were orally co-treated with isoniazid (200mg/Kg) and rifampicin (200mg/Kg).The results revealed that the INH+RIF co-treated rats significantly (p<0.05) increased the activities of liver function enzymes (ALT, AST and ALP) when compared with the normal control. There were significantly high levels (p<0.05) of malondialdehyde (MDA) and low levels of reduced glutathione (GSH) in the INH + RIF co-treated groups in contrast to the control. However, administration of extracts of A. boonei (250mg/kg and 500mg/kg doses) protected the animals against various degrees of oxidative damage, particularly in the aqueous extract treated rats. A similar trend was observed in the silymarin and vitamin E treated rats which showed normal levels of these parameters. The overall results from this study suggest that the aqueous extract of A. boonei leaf showed better hepatoprotective ability in contrast to the ethanol extract.