Erythorbic acid (isoascorbic acid, D-araboascorbic acid) is a

stereoisomer In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...

(C5 epimer) of

ascorbic acid Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent. Asco ...

(

vitamin C Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription di ...

). It is synthesized by a reaction between methyl 2-keto-D-gluconate and

sodium methoxide Sodium methoxide is the simplest sodium alkoxide. With the formula , it is a white solid, which is formed by the deprotonation of methanol. It is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base. ...

. It can also be synthesized from

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

or by strains of ''

Penicillium ''Penicillium'' () is a genus of Ascomycota, ascomycetous fungus, fungi that is part of the mycobiome of many species and is of major importance in the natural environment, in food spoilage, and in food and drug production. Some members of th ...

'' that have been selected for this feature. It is denoted by

E number E numbers, short for Europe numbers, are codes for substances used as food additives, including those found naturally in many foods, such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

E315, and is widely used as an

antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...

in processed foods.

Health effects

Clinical trials have been conducted to investigate aspects of the nutritional value of erythorbic acid. One such trial investigated the effects of erythorbic acid on vitamin C metabolism in young women; no effect on vitamin C uptake or clearance from the body was found. A later study found that erythorbic acid is a potent enhancer of nonheme-iron absorption, just like ascorbate. This is thought to be due to it exerting the same iron-reducing and iron-chelating activity as ascorbic acid. Neither of these reactions is mediated by an enzyme, which would confer some chiral selectivity. It is twice as effective as ascorbic acid in enhancing non-heme iron absorption. Americans are estimated to ingest 200 mg of erythorbic acid per day, making it a very important factor in understanding iron absorption.

Uses

Since the U.S. Food and Drug Administration banned the use of

sulfites Sulfites or sulphites are chemical compound, compounds that contain the sulfite ion (IUPAC nomenclature of inorganic chemistry, systematic name: sulfate(IV) ion), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous ...

as a

preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or ...

in foods intended to be eaten fresh (such as salad bar ingredients), the use of erythorbic acid as a food preservative has increased. It is also used as a preservative in cured meats and frozen vegetables. Much like ascorbic acid, it increases nitrosylation of the central iron atom of muscle

myoglobin Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle, skeletal Muscle, muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compar ...

, resulting in the formation of reddish-brown nitrosomyoglobin and the characteristic pink color of nitrosohemochrome or nitrosyl-heme upon cooking. Again like ascorbic acid, it reduces the formation of nitrosamines.

History

It was first synthesized in 1933 by the German chemists Kurt Maurer and Bruno Schiedt.

Production

Erythorbic acid is very easily produced by fermentation, being obtainable in just one step compared to ascorbic acid's two. A number of ''

'' naturally produce this chemical from glucose. This is the original process developed in the 1960s, but it has low volumetric efficiency and glucose yield compared to the modern method. Today the industrial process is quite similar to the Reichstein process used for ascorbic acid, only chirally flipped. Microbial fermentation first produces a 2-keto-sugar acid, e.g. by ''

Pseudomonas fluorescens ''Pseudomonas fluorescens'' is a common Gram-negative, rod-shaped bacterium. It belongs to the ''Pseudomonas'' genus; 16S rRNA analysis as well as phylogenomic analysis has placed ''P. fluorescens'' in the ''P. fluorescens'' group within the genu ...

'' AR4 converting glucose to 2-keto-D-gluconate. Then chemical rearrangement produces the product.

Economics

Like ascorbic acid, the production of erythorbic acid is concentrated in China. Its price is less volatile than that of ascorbic acid, making it an attractive alternative in non-nutritive uses in times of high ascorbic acid prices.

Related compounds

The structurally similar C5 sugar acid, D-erythroascorbic acid, is made by

baker's yeast Baker's yeast is the common name for the strains of yeast commonly used in baking bread and other bakery products, serving as a leavening agent which causes the bread to rise (expand and become lighter and softer) by converting the fermentable ...

and other fungi, acting as an antioxidant in their own cells. It is made by and has some antioxidant activity in '' Manduca sexta''. It has no industrial use, however.

References

{{reflist Food antioxidants E-number additives Substances discovered in the 1930s