Background: Citrullus lanatus seeds are known to be highly nutritious, and rich sources of phenolic compounds. They are usually milled into flour and used for making sauces, snacks, and cooking oil.

Aim: The present study investigated the effect of methanol extract of C. lanatus seed on hematological profile and tissue histology of normal Wistar rats.  

Methods: Adult male Wistar rats (n = 35) weighing 130 to 170 g (mean weight = 150 ± 20 g) were randomly assigned to 7 groups (5 rats/group): normal control, Tween 80 control, and five treatment groups. Rats in the treatment groups received graded doses of the extract (10 - 5000 mg/kg body weight, bwt) orally for 35 days. Hematological profile and rat tissue histology were assessed.

Results: Treatment of normal rats with graded doses of methanol extract of C. lanatus seed did not significantly affect the levels of hematological parameters, as well as absolute and relative weights of liver and kidneys (p > 0.05). Results of histopathological examinations showed that methanol extract of C. lanatus seed did not significantly alter the histology of rat liver, kidney and heart (p > 0.05). Graded doses of the extract induced progressive vasodilatation and mild congestion in the selected organs, thereby favoring increased blood flow in the tissues.

Conclusion: These results indicate that Citrullus lanatus seeds have beneficial effect on hematological indices and may not be toxic to rat tissues/organs.