Effect of heading on some micronutrients, anti-nutrients and toxic substances in <i>Amaranthus cruentus</i> grown in Minna, Niger State

Abstract

Pot experiment was conducted to determine the effect of heading (fruiting) on antinutrients (soluble and total oxalates), toxic substances (cyanide and nitrate) and some micronutrients viz; vitamin C, β-carotene (provitamin A) and mineral elements (Fe, Mg, Cu, Zn, Ca Na and K) in Amaranthus cruentus grown in nitrogen and non-nitogen treated soil. The vegetable leaves were harvested at both market maturity (vegetative phase) and heading (reproductive phase) and were subjected to chemical analysis. Results obtained showed that the vitamin C, cyanide, soluble and total oxalates contents in the vegetable were significantly elevated (p < 0.05) during heading irrespective of soil nitrogen levels. Nitrate and β-carotene contents decreased significantly (p < 0.05) during heading except that the decrease in β-carotene was not significant in vegetable treated with nitrogen fertilizer. Similarly the result also revealed that the Mg, Zn, Ca and K content were not significantly affected with heading of the vegetable. However, the Fe content was increased, while the Ca and Na contents were reduced significantly (p < 0.05) with heading. The result concludes that harvesting of the vetagetatble at vegetative phase (market maturity) generally reduce the levels of most of the plant toxins and still conserve most of the micronutrients in an amount to meet our dietary requirements.