Chemical Studies of Some Nigerian Vegetables

Abstract

Three Nigerian vegetables, Solatium melongena, Solarium nodiflorum and Vernonia amygdalina were analysed for oxalate, cyanide, minerals and food value. The edible leaves were low in oxalate and so involve no danger of oxalate toxicity, or decrease in their nutritive value due to the presence of oxalic acid. The content of hydrocyanic acid was also negligible and would, in any case, be lost during cooking. Aluminium contents were very high and could possibly be regarded as constituting a toxic level. The calcium content would provide about 4-7 per cent of the daily requirement for adults, who could depend solely on these vegetables for their daily iron requirements. The leaves were also good sources of protein. All these factors make the vegetables important dietary components in Nigeria and they could serve as a protein supplement, especially in villages where children can not get enough protein from meat, milk and cheese.Little is known about the chemical composition of the indigenous vegetables consumed in Nigeria. In addition to animal products and the starchy cereals and tubers, vegetables and pulses form a third important source of food and assume increasing importance where diets contain inadequate amounts of animal protein foods. The work described here forms part of a comprehensive study of the composition of some Nigerian vegetables, where about fifteen species are used but the most commonly consumed are six from the natural orders Solanaceae and Cruciferae. MATERIALS AND METHODSIn this work Solanum melongena, Solarium nodiflorum and Vernonia amygdalina were studied. S. nodiflorum and V. amygdalina produce bitter leaves which are sold in the market as pot-herbs and are eaten only after cooking, e.g. in soups. The leaves of both species are also used medicinally. S. melongena bears fruits which can be eaten either raw or cooked as a vegetable. Leaves of the three species were gathered over a three month period from plants of varying ages, so as to represent the type of sample that might be gathered for a meal, and were dried at 1 oo°C overnight and finely ground. Samples intended for oxalic and hydrocyanic acid determinations were given only a preliminary rinsing. Dry matter determinations were done on separate samples.Oxalate content was determined by the method of Dye (1956), with slight modifications. For soluble oxalate a 2 gm sample was digested in a water bath using 200 ml. of distilled water, filtered and diluted to 250 ml. Two 50 ml. aliquots of the extract were then evaporated to about 25 ml. with 6N HC1 and the brown precipitate which separated was filtered and washed with hot water. The combined solution and wash were titrated with concentrated ammonia until the salmon pink colour of a methyl-red indicator changed to faint yellow.

Effect of Different Weed Control Practices On Proximate Composition, Nutrient Concentration and Uptake of Maize (Zea Mays L.)

“…In 2005, the highest N was in mulched plots while the lowest was in the un weeded plots. N levels in both years were below the limit of 1.88% established by [5]. In 2004, the highest P was in mulched plot (0.27%) which was at par with Primextra treated plot (0.26% ) while the lowest was in no weeding plot.…”

“…In 2004, K content ranged from 0.18 to 0.25% while in 2005 it ranged from 0.17 to 0.24% .In both years, the highest K content was in mulched plot while the lowest was in no weeding plot. K levels were below the limit of 0.38 % [5]. Ca level ranged from 0.27 to 0.36% while in 2005 it ranged from 0.26 to 0.34%.…”

“…In both years , the highest Ca was in mulched plot while the lowest was in no weeding plot. Ca level was above the limit of 0.10 % [5]. In 2004, Mg ranged from 0.10 to 0.17% while in 2005 it ranged from 0.09 to 0.16%.…”

“…In 2005, the highest P was in mulched plot (0.26%) which was at par with Primextra treated plot (0.25% ) while the lowest was in no weeding plot. The P levels were below the limit of 0.41% [5]. In 2004, K content ranged from 0.18 to 0.25% while in 2005 it ranged from 0.17 to 0.24% .In both years, the highest K content was in mulched plot while the lowest was in no weeding plot.…”

“…Proximate composition of the grains by [3] showed that crude protein ranged from 10.67 to 11.25% ,lipid (4.17 to 5% ), crude fibre (2.07 to 2.97%), and carbohydrate (65.63 to 70.23%) while [4] noted that crude ash ranged from 1.4 and 3.3%. The mineral composition of the maize grain consists of 1.88% nitrogen, 0.41% phosphorous, 0.38% potassium, 0.10% calcium and 0.12% magnesium [5]. Despite the usefulness of this crop, its production is hampered as result of weed infestation.…”