Acute and sub-acute toxicity study of the root extracts of Fagaropsis hildebrandtii in mice and evaluation of their antimicrobial effects [version 1; peer review: 1 approved with reservations]

Background: Among the Kamba community of Kenya, roots of Fagaropsis hildebrandtii (FH) are boiled and used in managing cough, fertility problems, and microbial infections. The safety of this plant in oral administration and the validity of the ethnomedical claims is unverified. This study evaluated the toxicity of the aqueous and hexane root extracts of FH in mice and antimicrobial effects against Staphylococcus aureus, Salmonella typhimurium and Candida albicans. Methods: Doses (300 and 2000mg/kg) of the extracts were administered orally to mice for 14 days. The weight, feed, and water consumption, organ weight of mice and gross macroscopy of the liver were used in evaluating acute toxicity. Mice were additionally treated with 250, 500, and 1000mg/kg body weight doses of the extracts for 28 days and haematological, biochemical, and histological parameters noted. The minimum inhibitory and minimum bactericidal/fungicidal concentrations (MIC; MBC/MFC) of the extracts against the aforementioned pathogens were determined by broth dilution. Results: Acute oral toxicity of the extracts was >2000mg/kg, there were dose dependent changes in haematological and biochemical parameters, all female mice died when treated with doses of 1000mg/kg and doses ≥500mg/kg caused tubular degeneration and haemorrhage of the kidney, cloudy swelling of hepatocytes, and multifocal necrosis and pyknosis in the liver. The MBC/MIC ratio of each of the extracts against Staph. aureus and S. typhimurium was 2, while C. albicans was not sensitive to any of the extracts. Conclusions: Long term use of root extracts of FH was associated with dose-dependent changes in the kidney and liver of mice and changes in biochemical and haematological parameters. Root extracts of FH are bactericidal against Staph. aureus and S. typhimurium but have no effect on C. albicans. Future work should aim at identifying the metabolites responsible for the observed toxic and bactericidal effects of the roots of FH.