Nutritional Evaluation of the Leaf Meal of <i>Gongronema latifolia</i>

Abstract

Background: The leaves of G. latifolia have long been employed in ethnomedical practices, and as food additive among the local populations in Nigeria. This study was carried out to evaluate the nutritive value of G. latifolia through the proximate, mineral and phytochemical analysis of G. latifolia leaf meal (GLLM), as well as analysis of amino acid profile of GLLM protein. Methods: Standard analytical procedures were employed for proximate, mineral and phytochemical analysis of GLLM, and amino acid analysis of GLLM protein. Results: Values obtained for proximate fractions on dry matter basis were: crude protein, 14.25%; Ether extract, 2.84%; and Ash, 6.26%. Others included Crude Fiber, 2.84%; Nitrogen free extractive, 60.39%, and Metabolizable energy, 2903.41Kcal/kg. The concentrations (mg/100g) of the five minerals investigated were Calcium, 10.80; Magnesium, 45.0; Potassium, 486.0; Sodium, 3.86, and Phosphorus, 395.0. Amino acid analysis of the leaf meal protein of the plant revealed that it contains nutritionally important essential and non-essential amino acids in concentrations that compare favorably with standard provisional requirement pattern: The total amino acids (TAA) content was 66.38g/100g protein; Total Essential amino acid (TEAA) with histidine was 32.53g/100g protein; Total Non-essential Amino acid (TNEAA) was 33.85g/100g protein; Percentage Total Essential Amino acid with Histidine was 49.01 protein; Percentage Essential Amino acid without Histidine recorded 45.71g/100g protein; Percentage Total Non-essential Amino acid was 50.99g/100g protein. The amino acid scores, vis-avis standard provisional scoring pattern were: Leucine, 95.7%; Isoleucine, 85.0%; Lysine, 72.7%; Methionine + cysteine, 48.6%; Phenylalanine + Tyrosine, 115.0%; Threonine, 75.0%; Valine, 80.0% The amino acids which were in abundance relative to others were: Glutamic acid, Aspartic acid, Leucine, Arginine, Valine, Phenylalanine, Lysine, Glycine and Isoleucine with the values of 9.27, 7.75, 6.70, 4.42, 4.09, 4.01, 3.97, 3.60 and 3.39 (g/100g protein), respectively. However, the first limiting amino acid(s) recorded in its amino acid profile were the two Sulphur-containing amino acids, methionine + cystein, the sum of which scored 48.60% in the amino acid scoring system. The phytochemical factors studied and their percentage compositions wer: alkaloids, 1.03%; flavonoids, 0.37%; saponins, 0.47% and tannins 0.55%. Other phytochemicals measured (mg/100g) included Phenols, 0.17; Phytates, 0.12, and Cyanogenic glycosides, 7.07. Conclusion: The result of this study suggests that Gongronema latifolia could contribute significant nutritional benefits to human and livestock nutritional needs. However, further research is needed to ascertain specific administration regimen of GLLM or the phyto-nutrients of G. latifolia leaf extracts.