Phytochemistry and Toxicity of Methanol Root Extract of Costus lucanusianus

Costus lucanusianus (ginger lily or monkey sugarcane) is a medicinal plant commonly used to treat various ailments in tropical Africa. The leaves, stem and sometimes the root have been exploited for this purpose. However, it is a common belief in the Niger Delta of Nigeria that the root is poisonous. This study investigated the phytochemical and acute toxicity profiles of the methanol root extract of the plant. Phytochemical screening was conducted using standard procedures to test for alkaloids, flavonoids, saponins, tannins, anthraquinones, glycosides, triterpenoids/steroids and carbohydrates. The median lethal dose (LD50) was determined using the Arithmetic method of Reed and Muench. This was followed by haematologic, liver and kidney functionality assays at doses of 14, 29 and 58 mg/kg of the methanol root extract. The result obtained showed that the extract contained flavonoids, saponins, triterpenoids and steroids among others, but anthraquinones and alkaloids were not present. The median lethal dose (LD50) value obtained for the extract was 288 mg/kg. The haematologic assay showed significant, p<0.001, dose-dependent decrease in red blood cell parameters and also some white blood cell parameters (such as white blood cell, neutrophil, monocytes and eosinophil counts). Furthermore, the serum levels of the liver enzymes, electrolytes (except K+), urea and creatinine increased significantly as the doses increased. From the foregoing, it could be concluded that the root of Costus lucanusianus is toxic to the kidney and liver and could be a blood poison (hemotoxic). This confirms the ethnobotanical belief that this part of the plant (root) is poisonous.