Analysis, Nutrition, and Health Benefits of Tryptophan

Abstract

Tryptophan is an essential plant-derived amino acid that is needed for the in vivo biosynthesis of proteins. After consumption, it is metabolically transformed to bioactive metabolites, including serotonin, melatonin, kynurenine, and the vitamin niacin (nicotinamide). This brief integrated overview surveys and interprets our current knowledge of the reported multiple analytical methods for free and protein-bound tryptophan in pure proteins, protein-containing foods, and in human fluids and tissues, the nutritional significance of l-tryptophan and its isomer d-tryptophan in fortified infant foods and corn tortillas as well the possible function of tryptophan in the diagnosis and mitigation of multiple human diseases. Analytical methods include the use of acid ninhydrin, near-infrared reflectance spectroscopy, colorimetry, basic hydrolysis; acid hydrolysis of S-pyridylethylated proteins, and high-performance liquid and gas chromatography-mass spectrometry. Also covered are the nutritional values of tryptophan-fortified infant formulas and corn-based tortillas, safety of tryptophan for human consumption and the analysis of maize (corn), rice, and soybean plants that have been successfully genetically engineered to produce increasing tryptophan. Dietary tryptophan and its metabolites seem to have the potential to contribute to the therapy of autism, cardiovascular disease, cognitive function, chronic kidney disease, depression, inflammatory bowel disease, multiple sclerosis, sleep, social function, and microbial infections. Tryptophan can also facilitate the diagnosis of certain conditions such as human cataracts, colon neoplasms, renal cell carcinoma, and the prognosis of diabetic nephropathy. The described findings are not only of fundamental scientific interest but also have practical implications for agriculture, food processing, food safety, nutrition, and animal and human health. The collated information and suggested research need will hopefully facilitate and guide further studies needed to optimize the use of free and protein-bound tryptophan and metabolites to help improve animal and human nutrition and health.

Diet and Mental Health: Review of the Recent Updates on Molecular Mechanisms

“…Proteins and amino acids derived from dietary intake can positively influence sleep quality and duration by modulating neurotransmitters and neuromodulators expression [16]. Among the most studied, tryptophan, an essential amino acid, is of major interest because it acts as an upstream precursor of bioactive metabolites related to sleep, including serotonin and melatonin [17]. Glycine, a non-essential amino acid, may exert a positive action toward sleep quality by reducing the core body temperature exerting an excitatory and inhibitory role on neurotransmission via N-methyl-d-aspartate-type glutamate receptors and glycine receptors, respectively [18].…”

Determination of Free Tryptophan in Beer Samples by Capillary Isotachophoretic Method

“…Tryptophan (Trp) is large neutral amino acid (LNAA) and precursor for brain neurotransmitters (serotonin, melatonin, tryptamine, quinolinic acid and kynurenic acid). According to Friedman (2018), dietary Trp and its metabolites may contribute to the therapy of many diseases, cognitive function, depression, sleep and social function. However, this hypothesis is still under discussion (Soh and Walter 2011).…”

Phenolic Content and Antioxidant Activity of Extracts of 12 Melon (Cucumis melo) Peel Powders Prepared from Commercial Melons

“…For example, Mallek‐Ayadi, Bahloul, and Kechaou () found that Cucumis melo seed protein contains the 129.91 g tryptophan per kg protein. This melon seed protein containing the exceptionally high level of tryptophan might ameliorate the adverse effects of several diseases that have been reported for the amino acid tryptophan (Friedman, ). Clinical studies are needed to investigate this further.…”