Objective: Thymoquinone (Nigella sativa), one of the popular phytotherapy bioactive substances, is an antioxidant and anti-inflammatory substance with known hepatoprotective activity. In this study, we investigated whether thymoquinone has preventive effects on the development of hepatic encephalopathy in rats with hepatic encephalopathy model at two different doses.

Methods: Healthy albino Spraque-dawley rats were randomized into 4 different groups: healthy negative control group, positive control group in which hepatic encephalopathy was induced by intraperitoneal thioacetamide 200 mg/kg, Thymoquinone 10 mg/kg and Thymoquinone 20 mg/kg treatment groups. Thymoquinone was administered to the thymoquinone treated groups by gavage for 14 days, and then a hepatic encephalopathy model was induced with 200 mg/kg thioacetamide for three days. All rats were subjected to locomotor activity tests twice, once at the beginning and once at the end, and serum ammonium levels were measured and compared to determine whether the hepatic encephalopathy model occurred.

Results: While the baseline locomotor activity tests of the groups included in the study were not statistically different, the final locomotor activity tests were found to be statistically significantly different (p<0.05). In the post-hoc analysis, it was found that Thymoquinone 10 mg/kg group was statistically significantly different (p<0.05) in most of the locomotor activity tests from the positive control group in which hepatic encephalopathy model was created, and on the contrary, it had similar results to the healthy negative control group (p>0.05). Serum ammonium levels were lower in both thymoquinone groups compared to the positive control group, but not statistically differed (p>0.05).

Conclusion: Low dose Thymoquinone (10 mg/kg) group had similar results with the healthy group in both locomotor activity tests and serum ammonium levels. Thus, low dose Thymoquinone offers a promising treatment opportunity within the scope of preventive medicine for individuals at high risk of developing hepatic encephalopathy.