Hibiscus sabdariffa, a plant widely used in traditional medicine and investigated for various biological activities, was evaluated to determine its toxicological and safety profile in rabbits, where it is commonly used as forage. The in vitro antioxidant properties of the aqueous extract of Hibiscus sabdariffa calyx (AE-HsC) at concentrations of 25, 50, 100, 200, and 400 µg/mL were assessed using 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) spectrophotometric assays. Twenty (20) rabbits were used for the in vivo sub-chronic toxicity study and were randomly assigned into four groups of five rabbits each. Groups 2–4 received AE-HsC at doses of 5, 50, and 500 mg/kg body weight (bwt) per os (p.o.) once daily (semel in die; s.i.d.) for 90 days, while Group 1 (control) received 2 mL/kg of distilled/deionised water. Signs of toxicity and body weights were monitored throughout the study, and blood samples were collected at the end of the experimental period for haematological and serum biochemical analyses. Thereafter, representative liver and kidney tissues were collected from animals euthanised with 50 mg/kg bwt sodium pentobarbital for histopathological evaluation. The in vitro antioxidant activity of AE-HsC increased dose-dependently, comparable to that of standard ascorbic acid. Body weight increased significantly (P < 0.05) during the early phase of extract administration but decreased towards the end of the study, particularly at 500 mg/kg bwt. A significant (P < 0.05) increase in white blood cell count and lymphocyte percentage was observed in rabbits administered 50 and 500 mg/kg AE-HsC, respectively, while slight bile duct hyperplasia was observed at 500 mg/kg compared with the control group. Therefore, Hibiscus sabdariffa extract may be considered relatively non-toxic at low doses (5 and 50 mg/kg) during sub-chronic administration in rabbits.
Ahur et al. (Sun,) studied this question.