In Vitro and In Vivo Toxicological Evaluation of Avicennia africana P: Beauv. (Avicenniaceae) Leaf Extract in a Rat Model

Avicennia africana is an important ethnomedicinal plant that has long been used to treat malaria and several other diseases. Despite the plant's antimalarial and other therapeutic properties, there is limited evidence-based data on its potential toxicity. Hence, the purpose of the current study was to assess the safety of A. africana leaf ethanolic extract (AAE). The study was designed to ascertain the cytotoxic effects of the crude extract on red blood cells (RBCs) as well as the acute and subacute toxicity in Wistar albino rats in accordance with Organization for Economic Co-operation and Development (OECD) guidelines "Test No. 423" and CPMW/SWP/1042/99. The pulverized, shade-dried plant leaves were sequentially macerated with 70% ethanol to obtain the crude extract (AAE). The extract's cytotoxic activity (CC₅₀) against the uninfected human red blood cells (RBCs) was determined using the 3-(4,5-Dimethylythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. For the acute toxicity studies, the rats (male and female) were divided randomly into six groups of five rats (n = 5) and dosed orally once with the following dose levels: 100, 300, 1000, 3000, and 5000 mgkg^-1, p.o. of the extracted AAE, with the control group receiving only the vehicle. In the repeated dose toxicity studies, the rats (both sexes) were orally administered daily with AAE at 100, 300, and 1000 mgkg^-1 for 14 days. Rat body weights were measured, and blood samples were tested for haematological and biochemical markers. Internal organs like the heart, kidney, liver, and spleen were collected, inspected, and weighed, and histological examinations were performed. The median lethal dose (LD₅₀) value is greater than 5000 mgkg^-1 body weight, with no significant change in bodyweight or relative organ weight (ROWs) of the extract-treated groups or control group. The extract showed greater cytotoxicity activity (CC₅₀), which was >100 μg/mL, compared to the reference drug (artesunate).The dosage groups of 100 and 300 mgkg^-1bwt had neutrophilia and lymphocytopenia (p < 0.05). However, changes in these haematological parameters may not be dose dependent and could be stress related. All the serum biochemical markers studied in rats given AAE did not show any significant change (p > 0.05). Histopathological examination of internal organs of AAE-treated rats did not show any significant abnormalities resulting from the extract treatment compared to the control group. Based on the findings in the present study, the LD50 value of AAE was found to exceed 5000 mgkg^-1 in the acute toxicity test, while the no observed adverse effect level (NOAEL) in rats was 1000 mgkg^-1 p.o. In the sub-acute toxicity tests. Histopathological analysis revealed no morphological abnormalities in the vital organs.