Determination of Anti-nutrients and Toxic Substances of Selected Fresh Leafy Vegetables Obtained from Minna Town, Nigeria

Abstract

Determination of antinutrients and toxic substances in leafy vegetables is an imperative facet in nutritional studies as it establishes the baseline concentrations index for phytotoxins in the vegetables. Concentrations of cyanide, nitrate, soluble and total oxalates were quantitatively determined in the common leafy vegetables (Amaranthus cruentus, Hibiscus sabdariffa, Corchorus olitorius, Telfairia occidentalis and Vernonia amygdalina) consumed in Minna, Niger State, Nigeria, using colourimetric and titrimetric methods. The results show  that the concentration of cyanide in the leafy vegetables is within the permissible level of 200 mg/kg fresh weight while the concentration of nitrate in V. amygdalina and H. sabdariffa is within the acceptable daily intake of 219.00 mg/day, those of A. cruentus, C. olitorius and T. occidentalis is enough to induce toxicity in man. The soluble and total oxalates content in the vegetables are higher than the permissible level except that the concentration of soluble oxalate in H. sabdariffa is within the acceptable level of 250 mg/100 g. The results suggest that while the concentrations of cyanide in the analysed vegetables and nitrate in V. amygdalina and H. sabdariffa are safe for consumption, the concentrations of soluble and total oxalates in the vegetables and nitrate in A. cruentus, C. olitorius and T. occidentalis may contribute to nutritional problems if ingested without proper processing.

Keywords: Leafy vegetables, toxic substances, cyanide, nitrate, oxalates