Methods: Twenty-five rats were acclimatized for two weeks and randomized into five groups. Group I was untreated controls, while each rat in groups III–V was given a single intraperitoneal administration of paracetamol (800 mg/kg b.w.). Prior to the administration of paracetamol, rats in groups II and IV were orally given Costus afer extract at 200 mg/kg b.w, while rats in group V were given 400 mg/kg b.w. extract once daily for four days. In the other experiment, hydrogen peroxide was used to induce erythrocyte damage (after isolating erythrocytes from whole blood) and subsequently incubated with the extract at different concentrations. Markers for tissue and erythrocyte damage were assessed in serum, tissue homogenates, and erythrocytes. 

Results: Paracetamol caused marked elevations (p < 0.05) in the levels of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), alkaline phosphatase (ALP), urea, and creatinine in serum. The levels of thiobarbituric acid reactive species (TBARS) in both the liver and the kidney were also raised when compared to untreated control (p < 0.05) while the activities of superoxide dismutase (SOD) and catalase (CAT) were reduced when compared to untreated controls (p < 0.05). Pretreatment of rats with Costus afer extract (p.o.) caused a significant reduction in the serum levels of ALT, AST, ALP, urea, creatinine, and tissue TBARS closer to the control values (p < 0.05). Pretreatment of rats with the plant extract also increased the activities of SOD and CAT in both the liver and the kidney. Apart from the levels of TBARS in the liver and CAT in the kidney, rats pretreated with 400 mg/kg b.w. extract showed greater response than in pretreatment with 200 mg/kg b.w. The extract also reduced the hydrogen peroxide-induced erythrocyte damage assessed as hemolysis and lipid peroxidation, which was concentration-dependent (p < 0.05). 

Conclusion: This indicated that Costus afer possesses the ability to protect the various tissues against chemical-induced injury.