Monosodium glutamate is a chemical compound, the sodium salt of glutamic acid, also called MSG. 

It takes the form of a white flaky powder

What it is used for and where

Cosmetics

Included in cosmetic hair care formulations to improve hair hydration, elasticity and flexibility. The amount generally included is 2% and monosodium glutamate works best in skin environments where the pH is between 5 and 9. The result it provides is easier combability and a lower risk of breakage. It is a good substitute for mineral oils.

Food

Its main application is as a food additive labelled as E621 on the European Food Additives List as a flavour enhancer,

It is added to make food tastier and has the technical function of a flavour enhancer. It is the typical additive found in Chinese cuisine and is generally added to make bland foods more appetising.

Below is a summary of the most interesting studies (abstracts) on monosodium glutamate.

Central nervous system cytotoxicity is linked to neurodegenerative disorders. The objective of the study was to investigate whether monosodium glutamate (MSG) neurotoxicity can be reversed by natural products, such as ginger or propolis, in male rats. Four different groups of Wistar rats were utilized in the study. Group A served as a normal control, whereas group B was orally administered with MSG (100 mg/kg body weight, via oral gavage). Two additional groups, C and D, were given MSG as group B along with oral dose (500 mg/kg body weight) of either ginger or propolis (600 mg/kg body weight) once a day for two months. At the end, the rats were sacrificed, and the brain tissue was excised and levels of neurotransmitters, ß-amyloid, and DNA oxidative marker 8-OHdG were estimated in the brain homogenates. Further, formalin-fixed and paraffin-embedded brain sections were used for histopathological evaluation. The results showed that MSG increased lipid peroxidation, nitric oxide, neurotransmitters, and 8-OHdG as well as registered an accumulation of ß-amyloid peptides compared to normal control rats. Moreover, significant depletions of glutathione, superoxide dismutase, and catalase as well as histopathological alterations in the brain tissue of MSG-treated rats were noticed in comparison with the normal control. In contrast, treatment with ginger greatly attenuated the neurotoxic effects of MSG through suppression of 8-OHdG and β-amyloid accumulation as well as alteration of neurotransmitter levels. Further improvements were also noticed based on histological alterations and reduction of neurodegeneration in the brain tissue. A modest inhibition of the neurodegenerative markers was observed by propolis. The study clearly indicates a neuroprotective effect of ginger and propolis against MSG-induced neurodegenerative disorders and these beneficial effects could be attributed to the polyphenolic compounds present in these natural products (1).

An excessive glutamate level can result in excitotoxic damage and death of central nervous system (CNS) cells, and is involved in the pathogenesis of many CNS diseases. It may also be related to a failure of the blood-spinal cord barrier (BSCB). This study was aimed at examining the effects of extended administration of monosodium glutamate on the BSCB and spinal cord cells in adult male Wistar rats. The glutamate was delivered by subarachnoidal application of glutamate-carrying electrospun nanofiber mat dressing at the lumbar enlargement level. Half of the rats with the glutamate-loaded mat application were treated systemically with the histone deacetylase inhibitor valproic acid. A group of intact rats and a rat group with subarachnoidal application of an 'empty' (i.e., carrying no glutamate) nanofiber mat dressing served as controls. All the rats were euthanized three weeks later and lumbar fragments of their spinal cords were harvested for histological, immunohistochemical and ultrastructural studies. The samples from controls revealed normal parenchyma and BSCB morphology, whereas those from rats with the glutamate-loaded nanofiber mat dressing showed many intraparenchymal microhemorrhages of variable sizes. The capillaries in the vicinity of the glutamate-carrying dressing (in the meninges and white matter alike) were edematous and leaky, and their endothelial cells showed degenerative changes: extensive swelling, enhanced vacuo-lization and the presence of vascular intraluminal projections. However, endothelial tight junctions were generally well preserved. Some endothelial cells were dying by necrosis or apoptosis. The adjacent parenchyma showed astrogliosis with astrocytic hypertrophy and swelling of perivascular astrocytic feet. Neurons in the parenchyma revealed multiple symptoms of degeneration, including, inter alia, perikaryal, dendritic and axonal swelling, and destruction of organelles. All the damage symptoms were slightly less severe in the rats given valproic acid treatment, and were absent from both the intact rats and the rats with 'empty' nanofiber mat dressing. These results demonstrate that glutamate-loaded nanofiber mat dressing can locally create glutamate levels capable of damaging BSCB and that the resulting damage can be mitigated with concurrent systemic valproate treatment (2).

A single intake of monosodium glutamate (MSG) can cause headaches and increased muscle sensitivity. MSG can induce mechanical sensitization in the masseter muscle and adverse effects such as headache and short-term rise in blood pressure (3).

Monosodium glutamate studies

• Molecular Formula: C₅H₈NNaO₄
• Linear Formula: NaOOCCH₂CH₂CH(NH₂)COOH · H₂O
• Molecular Weight: 169.112 g/mol
• UNII: C3C196L9FG
• CAS: 142-47-2    6106-04-3  16177-21-2  116268-41-8  51959-41-2  56974-54-0
• EC Number: 205-538-1  240-313-1  608-719-7  612-072-6
• FEMA Number: 2756
• PubChem Substance ID 329750495
• MDL number MFCD00150138
• Beilstein Registry Number 4164348

Synonyms:

• L-(+)Sodium glutamate
• Monosodium glutamate anhydrous
• Sodium glutamate
• sodium (2S)-2-amino-4-carboxybutanoate
• Sodium L-glutamate
• Glutamic acid, monosodium salt, L-
• sodium (2S)-2-amino-5-hydroxy-5-oxo-pentanoate
• Ancoma
• sodium 2-amino-5-hydroxy-5-oxopentanoate
• Vetsin
• L-Glutamic acid, monosodium salt
• Zest
• Sodium (S)-2-amino-4-carboxybutanoate
• Chinese seasoning
• L-Glutamic acid sodium salt
• Monosodium L-glutamate
• Accent (food additive)
• Glutamat sodny [Czech]
• L(+) Sodium glutamate
• Glutamate monosodium salt
• Sodium glutamate (VAN)
• Natrium L-hydrogenglutamat
• Natriumglutaminat [German]
• Glutamic acid, sodium salt
• Sodium L-glutamate (VAN)
• Monosodioglutammato [Italian]
• CCRIS 3625
• HSDB 580
• Ajinomoto
• Glutacyl
• Glutavene
• Sodium hydrogen glutamate
• Natriumglutaminat
• Glutamate Sodium
• l-Monosodium glutamate
• Glutamic acid, L-, sodium salt

References___________________________________________________________________

(1) Ginger and Propolis Exert Neuroprotective Effects against Monosodium Glutamate-Induced Neurotoxicity in Rats  Hussein UK, Hassan NEY, Elhalwagy MEA, Zaki AR, Abubakr HO, Nagulapalli Venkata KC, Jang KY, Bishayee A  Molecules. 2017 Nov 8;22(11). pii: E1928. doi: 10.3390/molecules22111928.

(2) Nanofiber mat spinal cord dressing-released glutamate impairs blood-spinal cord barrier  Sulejczak D, Taraszewska A, Chrapusta SJ, Dziewulska D, Nakielski P, Rafałowska J  Folia Neuropathol. 2016;54(4):392-404. doi: 10.5114/fn.2016.64818.  

(3) Headache and mechanical sensitization of human pericranial muscles after repeated intake of monosodium glutamate (MSG)  Shimada A, Cairns BE, Vad N, Ulriksen K, Pedersen AM, Svensson P, Baad-Hansen L.  J Headache Pain. 2013 Jan 24;14:2. doi: 10.1186/1129-2377-14-2.