2. Chemistry
Aspartame is the methyl ester of the dipeptide of the natural amino acids L-aspartic acid and L-phenylalanine. Under strongly acidic or alkaline conditions, aspartame may generate methanol by hydrolysis. Under more severe conditions, the peptide bonds are also hydrolyzed, resulting in the free amino acids.[6] In certain markets aspartame is manufactured using a genetically modified variation of E. coli.[7][8]Wikipedia
Two of the components of aspartame (phenylalanine and aspartic acid) are chiral, which means that they have two isomers that are non-superimposable mirror images. This means that the final aspartame molecule will have two stereogenic centers. If the incorrect enantiomers are used, the aspartame molecule will not have the correct shape to fit the binding site of the ‘sweetness’ receptors on the tongue.Source
In the synthesis of aspartame, the starting materials are a racemic mixture (equal quantities of both enantiomers) of phenylalanine, and aspartic acid. Only the L enantiomer of phenylalanine is used: this is separated from the racemate by reacting it with acetic anhydride and sodium hydroxide. If the product of this reaction is then treated with the enzyme porcine kidney acylase and an organic extraction with H+ carried out, the L enantiomer is found in the aqueous layer and the D enantiomer remains in the organic layer.
Treatment of L-phenylalanine with methanol and hydrochloric acid esterifies the –CO2H group, and this ester is then reacted with aspartic acid to give the final product. It is important that the amine group on aspartic acid is protected with carbobenzyloxy groups and the acid group nearest the amine protected with benzyl groups, to prevent the L-phenylalanine reacting with these and giving unwanted byproducts. The acid group that is required to react is activated with Castro’s reagent. Castro’s reagent is displaced as L-phenylalanine is added, but the protective groups must be removed after the reaction. Carbobenzyloxy is removed by a reaction with hydrogen and platinum (IV) oxide with methanol and chloroform; benzyl is removed by reaction with hydrogen/palladium/carbon plus methanol and chloroform, completing the aspartame synthesis.
Aspartame is hydrolysed in the body to three chemicals, aspartic acid (40%), phenylalanine (50%) and methanol (10%). Aspartic acid is an amino acid. Much research has been carried out to determine its behaviour in the body when it is taken in its free form, i.e. unbound to proteins. It is claimed that when it is ingested the blood plasma levels of aspartate and glutamate rise significantly. Both aspartate and glutamate act as neurotransmitters in the brain, carrying information from neuron to neuron. When there is an excess of neurotransmitter, certain neurons are killed by allowing too much calcium into the cells. This influx causes excessive numbers of free radicals to build up which kill the cells. The neural cell damage that is caused by excessive aspartate and glutamate is the reason they are referred to as ‘excitotoxins’: they ‘excite’ or stimulate the neural cells to death.
Phenylalanine is another amino acid and is found normally in the brain. It is advised that people with the genetic disorder, phenylketonuria (PKU) do not consume aspartame as they are unable to metabolize the phenylalanine that is produced on its hydrolysis. A high level of phenyalanine in the brain is extremely harmful and sometimes fatal.
Methanol is highly toxic; it is gradually released in the small intestine when the methyl group of the aspartame encounters the enzyme chymotrypsin. It has been pointed out that some fruit juices and alcoholic beverages contain small amounts of methanol. It is important to remember, however, that methanol never appears alone. In every case, ethanol is present, usually in much higher amounts; ethanol reduces the effects of methanol toxicity in humans.
Formaldehyde Exposure from AspartameSource
Aspartame breaks down into methanol, amino acids and several other chemicals. The methanol is quickly absorbed and converted into formaldehyde. The methanol found in foods and alcoholic beverages is also absorbed, but there are "protective chemicals" in these traditionally-ingested foods and beverages that prevent the conversion of methanol to formaldehyde.
Formaldehyde is known to cause gradual damage to the nervous system, the immune system and has recently been shown to cause irreversible genetic damage at long-term, low-level exposure. The calculated level of formaldehyde exposure is approximately 61.3mg for every liter of aspartame ingested. That is over twice the level necessary to cause irreversible genetic damage in humans and several times the level shown to cause chronic neurological, cardiovascular, musculoskeletal, and other symptoms in long-term industrial exposure research. The damage caused by formaldehyde from aspartame may be worsened by other aspartame breakdown chemicals, especially the aspartic acid.
LOL! I will try the stevia next.
