Nutrient and anti-nutrient components of some tropical leafy vegetables

Abstract

Several leafy vegetables species ( n = 17) found in Nigeria were analysed for their proximate chemical composition, mineral constituents, energy values, phytin and oxalate content in the fresh and air-dried material. The dry vegetables contained on average, 19·3 g/100 g crude protein (CP). 15·3 g/100 g crude fibre (CF), 12·7 g/100 g ether extract (EE), 17·4 g/100 g ash and 89·9 g/100 g dry matter (DM) while the fresh counterparts contained, on average, 4·2, 3·2, 0·6, 7·3 and 17·6 g/100 g CP, CF, EE, ash and DM, respectively. Marked variations were observed in the proximate compositions of all the vegetables analysed as indicated by the high coefficients of variation. Potassium, sodium, calcium and phosphorus were the most abundant minerals in the dry samples with mean values of 3·7, 3·8, 2·5 and 1·2 g/100 g, respectively. Similarly, mean values of 4·4, 6·0, 0·9 and 0·8 g/100 g, respectively, were recorded for potassium, sodium, calcium and phosphorus in the fresh samples. Copper was the least abundant mineral in both the fresh and the air-dried samples. The mean energy value was 2787 kcal/kg with a range of 2192 kcal/kg in Amaranthus hybridus to 3732 kcal/kg in Manihot esculentus. The dry vegetables generally had higher phytate and oxalate values than the fresh ones. There were distinct familial differences in these anti-nutrient constituents as indicated by the high coefficients of variation of 39·5 and 88·9% for phytate and oxalate, respectively. The nutritive potentials of the vegetables are highlighted. Dietary implications of the anti-nutrients are also discussed, and the need to develop food/feed safe programmes involving these inherent factors emphasised.