Phytochemical composition and toxicity of the aqueous extract of Parkia biglobosa pods in adult Clarias gariepinus

Abstract

The phytochemical composition and toxicological evaluation of the aqueous extract of Parkia biglobosa pods in adult Clarias gariepinus was investigated over a 96-h exposure period. The aqueous extract of the pods was freeze-dried and screened for its phytochemical constituents. This revealed the presence of glycosides, alkaloids, saponins, steroids and triterpenes, tannins, carbohydrates and flavonoids but no anthraquinones and fixed oils. The fish were exposed to varying concentrations of the extract in a static acute toxicity bioassay. The exposed fish showed initial signs of agitated and erratic movements followed by signs of respiratory distress and abnormal nervous compromise, including mortality in some of the exposed fish. No such obvious signs of toxicity were recorded in the unexposed control fish. The appearance and intensity of the signs were both concentrations and exposure period-dependent. Mean mortality was significantly (p<0.05) related to extract concentrations and exposure period. The median lethal concentration of the extract in exposed fish over the 96-h exposure period was calculated to be 115.38 mg/l. Parkia biglobosa pods contained some toxicologically active constituents that can be meaningfully exploited to harvest fish from water bodies. However, this should be done with great care as the abusive use (higher concentrations) of this extract could result in extract residues in the exposed fish that might pose a risk to the consumers of such fish.

Keywords: Clarias gariepinus, Parkia biglobosa pods, phytochemical constituents, toxicity.