Aspartame

Description

Aspartame is the most popular artificial sweetener in the United States. It is sold as sweeteners such as NutraSweet and Equal, but it is also incorporated into thousands of food products.

Description

The sweetener aspartame is a dipeptide ester sold under the tradenames Equal and NutraSweet, among others. It is formally a condensation product of aspartic acid with the methyl ester of phenylalanine; but the actual synthetic methods are more complex.
In 1968, a South African patent for synthesizing aspartame and other dipeptide sweeteners was awarded to James M. Schlatter and assigned to G. D. Searle (Chicago), now part of Pfizer. The equivalent US Patent (3,492,131) was awarded in 1970. But not until 1981 did the US Food and Drug Administration approve it for use in foods.
At one time, rumors held that aspartame is carcinogenic; but studies performed from 2006 through 2015 refuted this allegation. The FDA and National Cancer Institute supported these studies.
Aspartame’s sweetness is ≈200 times greater than that of sucrose. Its solubility and stability in aqueous media depend strongly on pH. It is most stable at pH 4.3, which makes it ideal for sweetening carbonated beverages. It is unstable at normal cooking and baking temperatures; but it can be used in “no-heat” recipes.
Aspartame is considered to mimic the qualities of sucrose (e.g., flavor, taste duration, and low aftertaste) better than other artificial sweeteners.

Description

Aspartame is a synthetic non-caloric sweetener that is metabolized to phenylalanine, aspartic acid, and methanol in the gut. Aspartame (80 mg/kg per day for 90 days) increases plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, induces hepatocyte degeneration and leukocyte infiltration in the liver, and reduces hepatic levels of reduced glutathione (GSH), oxidized glutathione (GSSG), and γ-glutamylcysteine (γ-GC) in mice. Formulations containing aspartame have been used as sweetening agents and flavor enhancers in foods and beverages.

Chemical properties

white powder or tablets

Chemical properties

Aspartame (N-L-aspartyl-L-phenylalanine-1-methyl ester, 3-amino-N-(a-carbomethoxy- phenethyl)-succinamic acid-N-methyl ester) is an intense sweetener widely used in foods and beverages. Its solubility in water is approximately 10 g/L at room temperature. Aspartame is not fully stable under common processing and storage conditions of foods and beverages with the highest stability around pH 4.3. Aspartame is about 200 times sweeter than sucrose with a clean, but slightly lingering sweetness. It is used as the single sweetener, but often also in blends with other intense sweeteners owing to synergistic taste enhancement and taste quality improvement often seen in such blends.
In the European Union, aspartame is approved as E 951 for a large number of food applications. In the United States, it is approved as a multipurpose sweetener for food and beverage uses and it is also approved in many other countries.

Chemical properties

Aspartame occurs as an off white, almost odorless crystalline powder with an intensely sweet taste.

Chemical properties

Aspartame has no odor, but has an intense sweet taste. It is a high intensity sweetener, about 160 to 200 times sweeter than sucrose. Normal digestive processes convert aspartame to phenylalanine, aspartic acid and methanol. Metabolism of aspartame in the body provides approximately 17 kJ (4 kcal)/g. The stability of aspartame is affected by moisture, pH and temperature. For a detailed description of this compound, refer to Burdock (1997).

Originator

Canderel,Searle,France,1979

History

Aspartame was discovered accidentally in 1965 during a search for drugs to treat gastric ulcers. James M. Schlatter, an organic chemist working for G. D. Searle & Company, was using aspartyl-phenylalanine methyl ester (aspartame) in a synthesis procedure and inadvertently got some of the compound on his hands.

The Uses of Aspartame

Aspartame is a high-intensity sweetener that is a dipeptide, provid- ing 4 cal/g. it is synthesized by combining the methyl ester of phenylalanine with aspartic acid, forming the compound n-l-alpha- aspartyl-l-phenylalanine-1-methyl ester. it is approximately 200 times as sweet as sucrose and tastes similar to sugar. it is compara- tively sweeter at low usage levels and at room temperature. its mini- mum solubility is at ph 5.2, its isoelectric point. its maximum solubility is at ph 2.2. it has a solubility of 1% in water at 25°c. the solubility increases with temperature. aspartame has a certain insta- bility in liquid systems which results in a decrease in sweetness. it decomposes to aspartylphenylalanine or to diketropiperazine (dkp) and neither of these forms is sweet. the stability of aspartame is a function of time, temperature, ph, and water activity. maximum stability is at approximately ph 4.3. it is not usually used in baked goods because it breaks down at the high baking temperatures. it contains phenylalanine, which restricts its use for those afflicted with phenylketonuria, the inability to metabolize phenylalanine. uses include cold breakfast cereals, desserts, topping mixes, chew- ing gum, beverages, and frozen desserts. the usage level ranges from 0.01 to 0.02%.

The Uses of Aspartame

A dipeptide ester about 160 times sweeter than sucrose in aqueous solution. A non-nutritive sweetener.

The Uses of Aspartame

Non-nutritive sweetener.

The Uses of Aspartame

Aspartame in powder form for limited uses such as cereals, powdered drinks, and chewing gum. When aspartame is used in baked goods and baking mixes, it should not exceed 0.5% by weight. Packages of the dry, free-fl owing aspartame are required to prominently display the sweetening equivalence in teaspoons of sugar.

The Uses of Aspartame

The chemical name for aspartame is L-aspartyl-L-phenylalamine methyl ester.
It is a white crystalline powder and is about 200 times as sweet as sucrose. It is noted for a clean, sweet taste that is similar to that of sucrose.
Aspartame is the most widely used artificial sweetener in the world. It was approved by the FDA for use in the USA in 1981, and now is approved for use in several other countries of the world. One of the drawbacks of aspartame is its instability to heat and acid. Under acidic conditions aspartame slowly hydrolyzes leading to a loss of sweetness, chemical interaction, and microbial degradation. The shelf life of the aspartame-sweetened products with high water content is limited to about 6 months, after which it breaks down into its constituent components and loses its sweetening abilities. At elevated temperatures, solid aspartame slowly releases methanol to form aspartyl phenylalamine and the dioxopiperazine. This reaction is especially favored at neutral and alkaline pH values. Because of this reason, aspartame cannot be used in hot baking foods.
Another disadvantage of aspartame was noticed in the human digestive system. When the body ingests aspartame, it breaks down into its three constituent components: phenylalamine, aspartate, and methanol. The phenylalamine and aspartate are handled by enzymes in the stomach and in the small intestine, while the methanol is transported to the liver for detoxification. The metabolism of phenylalamine requires an enzyme that is not produced by a small proportion of the population having a genetic disorder called phenyl keton uria (PKU). Aspartame should be avoided by persons suffering from PKU. A warning to PKU sufferers on aspartame-containing products is required in many countries.

Definition

ChEBI: A dipeptide composed of methyl L-phenylalaninate and L-aspartic acid joined by a peptide linkage.

Production Methods

Aspartame is produced by coupling together L-phenylalanine (or Lphenylalanine methyl ester) and L-aspartic acid, either chemically or enzymatically. The former procedure yields both the sweet aaspartame and nonsweet β-aspartame from which the α-aspartame has to be separated and purified. The enzymatic process yields only α-aspartame.

Production Methods

Aspartame is synthesized using the L enantiomer of phenylalanine. The L enantiomer is separated from the D enantiomer, the racemic mixture, by reacting it with acetic anhydride (CH₃₂

Preparation

By coupling the amino acids L-phenylalanine and L-aspartic acid, and the esterification of the carboxyl group of the phenylalanine moiety to produce the methyl ester. This esterification can occur before or after coupling. The crystallized slurry is centrifuged and the resulting “wet-cake” is washed to remove impurities.

Manufacturing Process

A solution of 88.5 parts of L-phenylalanine methyl ester hydrochloride in 100 parts of water is neutralized by the addition of dilute aqueous potassium bicarbonate, then is extracted with approximately 900 parts of ethyl acetate. The resulting organic solution is washed with water and dried over anhydrous magnesium sulfate. To that solution is then added 200 parts of Nbenzyloxycarbonyl- L-aspartic acid α-p-nitrophenyl, β-benzyl diester, and that reaction mixture is kept at room temperature for about 24 hours, then at approximately 65°C for about 24 hours. The reaction mixture is cooled to room temperature, diluted with approximately 390 parts of cyclohexane, then cooled to approximately -18°C in order to complete crystallization. The resulting crystalline product is isolated by filtration and dried to afford β- benzyl N-benzyloxycarbonyl-L-aspartyl-L-phenylalanine methyl ester, melting at about 118.5-119.5°C.
To a solution of 180 parts of β-benzyl N-benzyloxycarbonyl-L-aspartyl-Lphenylalanine methyl ester in 3,000 parts by volume of 75% acetic acid is added 18 parts of palladium black metal catalyst, and the resulting mixture is shaken with hydrogen at atmospheric pressure and room temperature for about 12 hours. The catalyst is removed by filtration, and the solvent is distilled under reduced pressure to afford a solid residue, which is purified by recrystallization from aqueous ethanol to yield L-aspartyl-L-phenylalanine methyl ester. It displays a double melting point at about 190°C and 245- 247°C.

Therapeutic Function

Sugar supplement

Biotechnological Production

Aspartame is produced from L-aspartic acid and L-phenylalanine and methanol or alternatively L-phenylalanine methyl ester. The standard process uses common chemical methods of peptide synthesis. Enzymatic coupling of the two amino acids is also possible. N-formyl-L-aspartic acid and L- or D.L-phenylalanine methyl ester can be condensed to aspartame by thermolysin-like proteases. The formylated aspartame can be deformylated chemically or with a formylmethionyl peptide deformylase to yield the sweetener.The enzymatic coupling does not require L-phenylalanine but can start from the racemic product obtained in chemical synthesis, and the remaining D-phenylalanine can be racemized again.
Production processes based on fermentation are available for the two main components, aspartic acid and phenylalanine.

General Description

Asp-Phe methyl ester (aspartame, APM, ASP), a dipeptide ester, is made up of phenyl alanine and aspartic acid. Its genotoxic effects have been investigated. Its interaction with certain hydrocolloids has been studied.

Pharmaceutical Applications

Aspartame is used as an intense sweetening agent in beverage products, food products, and table-top sweeteners, and in pharmaceutical preparations including tablets, powder mixes, and vitamin preparations. It enhances flavor systems and can be used to mask some unpleasant taste characteristics; the approximate sweetening power is 180–200 times that of sucrose.
Unlike some other intense sweeteners, aspartame is metabolized in the body and consequently has some nutritive value: 1 g provides approximately 17 kJ (4 kcal). However, in practice, the small quantity of aspartame consumed provides a minimal nutritive effect.

Biochem/physiol Actions

Asp-Phe methyl ester (Asp-Phe-OMe) is used as a synthetic sweeter, sugar substitute. Asp-Phe methyl ester is being studied for a variety of potential benefits as a nutrition supplement, such as the delay of osteoarthritis and modulation of rheumatoid factor activity. Asp-Phe methyl ester is being studied for its effect on thrombin activity and blood clotting.

Safety Profile

Human systemic effects byingestion: allergic dermatitis. Experimental reproductiveeffects. When heated to decomposition it emits toxicfumes of NOx.

Safety

Aspartame is widely used in oral pharmaceutical formulations, beverages, and food products as an intense sweetener, and is generally regarded as a nontoxic material. However, the use of aspartame has been of some concern owing to the formation of the potentially toxic metabolites methanol, aspartic acid, and phenylalanine. Of these materials, only phenylalanine is produced in sufficient quantities, at normal aspartame intake levels, to cause concern. In the normal healthy individual any phenylalanine produced is harmless; however, it is recommended that aspartame be avoided or its intake restricted by those persons with phenylketonuria.
The WHO has set an acceptable daily intake for aspartame at up to 40 mg/kg body-weight. Additionally, the acceptable daily intake of diketopiperazine (an impurity found in aspartame) has been set by the WHO at up to 7.5 mg/kg body-weight.
A number of adverse effects have been reported following the consumption of aspartame, particularly in individuals who drink large quantities (up to 8 liters per day in one case) of aspartame-sweetened beverages. Reported adverse effects include: headaches; grand mal seizure;memory loss;gastrointestinal symptoms; and dermatological symptoms. However, scientifically controlled peer-reviewed studies have consistently failed to produce evidence of a causal effect between aspartame consumption and adverse health events. Controlled and thorough studies have confirmed aspartame’s safety and found no credible link between consumption of aspartame at levels found in the human diet and conditions related to the nervous system and behavior, nor any other symptom or illness. Aspartame is well documented to be nongenotoxic and there is no credible evidence that aspartame is carcinogenic.
Although aspartame has been reported to cause hyperactivity and behavioral problems in children, a double-blind controlled trial of 48 preschool-age children fed diets containing a daily intake of 38 ± 13 mg/kg body-weight of aspartame for 3 weeks showed no adverse effects attributable to aspartame, or dietary sucrose, on children’s behavior or cognitive function.

Environmental Fate

Aspartame is nontoxic. However, individuals with the rare, genetic disease, phenylketonuria (PKU), cannot properly metabolize phenylalanine. Such individuals are detected by testing at birth and placed on special low-phenylalanine diets to control their blood phenylalanine concentrations. Thus, PKU individuals need to be aware that aspartame is a source of phenylalanine.

Metabolic pathway

The rate of aspartame degradation is faster in a phosphate buffer solution than in a citrate buffer solution at the same pH and buffer concentration. The primary mechanism by which aspartame degrades, the formation of diketo piperazine, involves the nucleophilic attack of carbonyl by the free amine, which requires proton transfer.

storage

Aspartame is stable in dry conditions. In the presence of moisture, hydrolysis occurs to form the degradation products L -aspartyl-Lphenylalanine and 3-benzyl-6-carboxymethyl-2,5-diketopiperazine with a resulting loss of sweetness. A third-degradation product is also known, β-L-aspartyl-L-phenylalanine methyl ester. For the stability profile at 258℃ in aqueous buffers.
Stability in aqueous solutions has been enhanced by the addition of cyclodextrins, and by the addition of polyethylene glycol 400 at pH 2. However, at pH 3.5–4.5 stability is not enhanced by the replacement of water with organic solvents.
Aspartame degradation also occurs during prolonged heat treatment; losses of aspartame may be minimized by using processes that employ high temperatures for a short time followed by rapid cooling.
The bulk material should be stored in a well-closed container, in a cool, dry place.

Incompatibilities

Differential scanning calorimetry experiments with some directly compressible tablet excipients suggests that aspartame is incompatible with dibasic calcium phosphate and also with the lubricant magnesium stearate. Reactions between aspartame and sugar alcohols are also known.

Regulatory Status

Accepted for use as a food additive in Europe and in the USA. Included in the FDA Inactive Ingredients Database (oral powder for reconstitution, buccal patch, granules, syrups, and tablets). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.