The effects of applied nitrogen fertilizer and leaf positions on levels of micronutrients, anti-nutrients and toxic substances in Amaranthus cruentus

The presence of antinutrients and toxic substances in vegetables limits the nutritional benefits of vegetables. The effects of age of plant and application of nitrogen fertilizer on the bioaccumulation of antinutrients (oxalate), toxic substances (cyanide and nitrate), micronutrients (vitamin C, β-carotene - provitamin A) and mineral elements (Fe, Mg, Cu, Zn, Ca Na and K) in Amaranthus cruentus were investigated using pot experiment. Leaves were harvested at market maturity (vegetative phase) at three different leaf positions, basal (oldest), middle (younger) and upper (youngest) and were subjected to chemical analysis. Results obtained showed that cyanide, nitrate and oxalate were concentrated significantly in the basal and middle positions. The concentration of β-carotene, vitamin C and Zn were significantly higher in the leaves in the middle part than in the basal and upper leaves. Similarly, Fe, Mg, Cu and Na contents were significantly higher in the basal leaves than in the middle and upper leaves, while the concentration of K was higher in the younger leaves. We concluded that consumption of the vegetable leaves from the upper leaf position will provide the dietary requirements of the analysed micronutrients with significant reduction in the levels of oxalate, cyanide and nitrate and associated health problems. Key words: Amaranthus cruentus, market maturity, micronutrients, anti-nutrients, toxic substances, vegetable, oxalate, nitrate, cyanide.