Phytochemical, Anti-nutrients and Toxicity Evaluation of Cleome gynandra and Solanum nigrum: Common Indigenous Vegetables in Zimbabwe

Abstract

Aim: This study assesses the phytochemical profiles, toxicity and anti-nutrient properties of two indigenous vegetables, Cleome gynandra and Solanum nigrum. Methodology: Aerial parts of S. nigrum and C. gynandra collected from wild populations were extracted in water and methanol solvents using the cold maceration procedure. Chemical tests to identify different phytochemicals and antinutrients were carried out using specified reagents. Toxicity of the plant extracts was tested using the Brine Shrimp (Artemia salina) lethality bioassay procedure. Results: Phytochemical tests indicated presence of alkaloids, steroids, flavonoids, cardiac glycosides, saponins, phenols and tannins in both S. nigrum and C. gynandra. Anthraquinones were only found in C. gynandra, whereas terpenoids and coumarin glycosides were found only in S. nigrum. The anti-nutrient levels in the vegetables were high; tannins (3.580 and 1.820 mg/                100 g), oxalates (21.560 and 24.97±0.156 g/100 g), saponins (71 and 42%), alkaloids (15.160 and 3.44%) and phytates (0.099±0.046 and 0.250±0.013%) in S. nigrum and C. gynandra respectively. The Brine Shrimp LC₅₀ values obtained were 0.67 and 1.84 mg/ml for methanol and water extracts of S. nigrum and 1.09 and 4.9 mg/ml for C. gynandra, respectively. Conclusion: The vegetables, C. gynandra and S. nigrum are rich sources of diverse phytochemicals. However, some phytochemicals are present in high levels and might act as anti nutritional factors interfering with absorption of food. C. gynandra is safe for consumption but S. nigrum contains some toxic phytochemicals and should not be taken regularly.