Crude herbal preparations of different Morinda plant species had been used in the treatment of ailments in Nigerian folk medicine with little or no attention directed to their toxicities. The aim of this study is to compare the effect of methanol fruit extracts of Morinda citrifolia (MCE) and Morinda lucida (MLE) on the liver. The active components in the fruits of these Morinda plant species were extracted with 90% methanol. Medium lethal doses of the extracts (LD50) were investigated using Lorke method. The extracts were administered to groups of rats (groups 1- 7) at the doses of 100, 200, and 400mg/kg b.w respectively by intubation, while group 1 received normal saline (control). Test and control animals were fed with normal rats’ feed and water. Two rats from each group were sacrificed every 7 days to collect blood for liver function tests using automatic analyzer Mind ray (BS – 120) Chemistry Analyzer. Also, the livers of rats were excised for histopathology using eosin and haematoxylin method of staining. The median lethal dose (LD50), revealed no death of mice even at 5000mg/kg b.w for both species of Morinda indicating that MCE and MLE were relatively safe. The alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) activity decreased non-significantly (p>0.05) in rats fed with both extracts showing that they could not have caused liver injury. Also there was non-significant decrease (p>0.05) in the total and conjugated bilirubin concentrations in the rats fed with both extracts when compare with the control rats. These results were supported with the histopathological results of the rats fed with both MCE and MLE which showed no significant difference (p>0.05) in the livers of test rats when compared with that of the control rats. The results from this study could suggest that MCE and MLE have no toxic effect on the liver. This could support the use of MCE and MLE in Nigeria folk medicine.

Keywords : Histopathological, Injury, Median lethal dose.