Assessment of oral and dermal toxicity of selected ethno-medicinal plants used to treat bacterial skin infections in Uganda using Wistar albino rats

Abstract

Introduction Erlangea tomentosa S. Moore, Plectranthus caespitosus Lukhoba and Psorospermum febrifugum Spach are used in traditional medicine for management of skin and other bacterial infections in Uganda. Unlike their efficacies, the toxicity profiles have not been investigated. Therefore, this study investigated the dermal and oral toxicities of these plants in Wistar albino rats. Methods Acute and repeated oral doses of the aqueous extracts (2000 and 5000 mg/kg bw; 200 and 400 mg/kg bw respectively) and dermal doses of the organic extracts (8000 and 10,000 mg/kg bw; 2000 and 5000 mg/kg bw respectively) were administered to Wistar albino rats following OECD guidelines with slight modifications. The occluded dermal irritation and modified mouse ear swelling tests were conducted to evaluate skin irritation and sensitization potentials of the medicinal plants. Throughout the study, clinical observations were recorded, and body weights were monitored periodically. Biochemical parameters, organ weights, and histopathological analyses of the liver, kidneys, heart, stomach, and small intestines were performed to detect any signs of systemic toxicity. Additionally, phytochemical screening was carried out to identify the major classes of phytochemicals in the selected plants. Results The leaf extract of E. tomentosa showed no signs of toxicity with acute oral administration at doses of 2000 and 5000 mg/kg bw. However, repeated oral exposure at 400 mg/kg bw resulted in liver injury. Whereas no acute dermal toxicity was observed for E. tomentosa, repeated dermal exposure at 200 and 400 mg/kg bw caused necrotizing liver hepatitis. Acute oral exposure to 5000 mg/kg bw) of P. febrifugum aqueous extract increased liver weight and temporarily elevated respiration, urination, and mobility, all of which resolved within 24 h. In contrast, repeated oral exposure at 400 mg/kg bw led to reduced liver and kidney weights, with biochemical markers indicating liver injury, although histopathology revealed no significant lesions. Dermal exposure to the organic extract did not cause skin irritation or sensitization. However, repeated dermal application at 2000, 5000 and 8000 mg/kg bw led to increased bilirubin, creatinine, and AST levels, alongside decreased urea and ALP levels, suggesting cholestasis and impaired kidney function. P. caespitosus demonstrated no signs of toxicity with acute oral administration at 2000 and 5000 mg/kg bw, and repeated oral exposure at 200 and 400 mg/kg did not cause organ toxicity. No acute dermal toxicity was observed, even with repeated exposure. Conclusion & recommendation No mortality or acute toxicity was observed with oral or dermal administration of E. tomentosa, P. febrifugum, and P. caespitosus extracts in Wistar albino rats, though repeated exposure to some extracts indicated potential liver and kidney toxicity. Phytochemical analysis revealed the presence of anthraquinones, coumarins, saponins, steroids, and tannins, suggesting further investigation is needed to fully understand their toxicological profiles.