Effect of fruiting on micronutrients, antinutrients and toxic substances in <i>Telfairia occidentalis</i> grown in Minna, Niger State, Nigeria

Abstract

A pot experiment was conducted to determine the effect of fruiting on antinutrients (soluble and total oxalates), toxic substances (cyanide and nitrate) and some micronutrients namely: vitamin C, β-carotene (provitamin A) and mineral elements [(sodium (Na), iron (Fe), magnesium (Mg), copper (Cu), Zinc (Zn), calcium (Ca) potassium (K)] in Telfairia occidentalis grown in nitrogen and non-nitrogen treated soil. Vegetable leaves were harvested at both market maturity (vegetative phase) and fruiting (reproductive phase), and were subjected to chemical analysis. Results showed that the cyanide and total oxalate concentrations were significantly higher at fruiting stage of vegetables grown on both control and nitrogen applied soil, while the nitrate and β-carotene concentration in T. occidentalis were significantly reduced irrespective of the soil nitrogen levels. Fruiting however, had no significant effect on soluble oxalate and vitamin C concentration in T. occidentalis grown under control and nitrogen treatment conditiond. The results also revealed that while Fe and Mg contents were increased, K and Cu content decreased significantly with fruiting in both control and nitrogen fertilization treatment. Similarly, the Na content in the vegetable was decreased significantly only when nitrogen fertilizer was used. The levels of Zn and Ca were not affected by fruiting. We conclude that consumption of the leaves of T. occidentalis at vegetative phase (market maturity) reduces the levels of most of the plant toxins and still retain most of the micronutrients in an amount to meet nutritional requirements.

Key words: Telfairia occidentalis, anti-nutrients, toxic substances, micronutrients, market maturity and fruiting, soil nitrogen levels.