Amino acid profiles of Solanum aethiopicum, Amaranthus hybridus, and Telfairia occidentalis, common leafy vegetables in Nigeria

The aim was to evaluate the amino acid compositions of three commonly consumed leafy vegetables (Solanum aethiopicum, Amaranthus hybridus, and Telfairia occidentalis) in Abakaliki, Ebonyi State. Leafy vegetables are important protective foods and beneficial for the maintenance of healthy living and prevention of diseases. The fresh leaves of A. hybridus, T. occidentalis, and S. aethiopicum were air-dried under room temperature for 1 week. The dried samples were further milled into a fine powder using a mechanical grinder and were stored in an air-tight plastic container. Amino acid content was determined using an applied Bio-system (phenylthiohydantoin, PTH) amino acid analyzer. Among amino acids determined in the vegetables, glutamic acid had the highest value with 12.59, 11.20, and 11.96 g/100 g protein, which was followed closely by leucine with 9.81, 7.94, 9.28 g/100 g protein, and aspartic acid with 8.99, 8.62, and 9.74 g/100 g protein in S. aethiopicum, A. hybridus, and T. occidentalis, respectively on dry weight bases. The leaf that contained the highest total amino acid (TAA) was S. aethiopicum with 88.69 g/100 g protein followed by T. occidentalis with 80.39 g/100 g protein while A. hybridus being the lowest, had 73.38 g/100 g protein. The limiting essential amino acid was tryptophan with 1.98 g/100 g protein while leucine with 9.0 g/100 g protein was the most abundant TAA. The percentage concentration of different groups of amino acid in vegetables revealed that total essential amino acid (TEAA) had 54.85%, total non-essential amino acid (TNEAA) had 48.27%, total neutral amino acid (TNAA) had 22.24%, total acidic amino acid (TAAA) had 32.48%, total basic amino acid (TBAA) had 11.53%, total aromatic amino acid (TArAA) had 11.89% while total sulfur amino acid (TSAA) had 3.94%. The results indicate that the vegetables studied are rich in essential amino acids and could serve as a good source of quality protein. Therefore, they could be recommended as food supplements, especially when animal proteins become more expensive as a source of protein.