Mandelic acid
Encyclopedia
Mandelic acid is an aromatic alpha hydroxy acid
with the molecular formula C6H5CH(OH)CO2H. It is a white crystalline solid that is soluble in water and polar organic solvent
s. It is a useful precursor to various drugs. Since the molecule is chiral
, it exists in either of two enantiomers
as well as the racemic
mixture, known as paramandelic acid.
, an extract of bitter almonds, with diluted hydrochloric acid
. The name is derived from the German
"Mandel" for "almond". Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase
and catechol-O-methyl transferase
.
Mandelic acid is usually prepared by the acid-catalysed hydrolysis of mandelonitrile
, which is the cyanohydrin
of benzaldehyde
. Mandelonitrile
can also be prepared by reacting benzaldehyde
with sodium bisulfite
to give the corresponding adduct, forming mandelonitrile
with sodium cyanide
, which is hydrolyzed
:
Alternatively, it arises by base hydrolysis of phenylchloroacetic acid and dibromacetophenone. It also arises by heating phenylglyoxal
with alkalis.
in skin care products. Mandelic acid is also advantageous in that it possesses antibacterial properties. Its use as a skincare modality was pioneered by Dr James E. Fulton, who developed vitamin A acid (tretinoin, Retin A) in 1969. On the basis of this research, dermatologists now suggest mandelic acid for a wide variety of skin concerns, from acne to wrinkles; it is especially good in the treatment of adult acne as it addresses both of these concerns. Mandelic acid products have been used as an alternative treatment for rosacea
sufferers, as it reduces inflammation and redness. Mandelic acid is also recommended for pre- and post-laser treatment, reducing the amount of redness and irritation caused by laser resurfacing.
The drugs cyclandelate
and homatropine
are ester
s of mandelic acid.
Alpha hydroxy acid
α-Hydroxy acids, or alpha hydroxy acids , are a class of chemical compounds that consist of a carboxylic acid substituted with a hydroxyl group on the adjacent carbon. They may be either naturally occurring or synthetic. AHAs are well-known for their use in the cosmetics industry...
with the molecular formula C6H5CH(OH)CO2H. It is a white crystalline solid that is soluble in water and polar organic solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
s. It is a useful precursor to various drugs. Since the molecule is chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
, it exists in either of two enantiomers
Optical rotation
Optical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose , solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms...
as well as the racemic
Racemic
In chemistry, a racemic mixture, or racemate , is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was "racemic acid", which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid.- Nomenclature :A...
mixture, known as paramandelic acid.
Isolation and synthesis
Mandelic acid was discovered while heating amygdalinAmygdalin
Amygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...
, an extract of bitter almonds, with diluted hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. The name is derived from the German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
"Mandel" for "almond". Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase
Monoamine oxidase
L-Monoamine oxidases are a family of enzymes that catalyze the oxidation of monoamines. They are found bound to the outer membrane of mitochondria in most cell types in the body. The enzyme was originally discovered by Mary Bernheim in the liver and was named tyramine oxidase...
and catechol-O-methyl transferase
Transferase
In biochemistry, a transferase is an enzyme that catalyzes the transfer of a functional group from one molecule to another . For example, an enzyme that catalyzed this reaction would be a transferase:In this example, A would be the donor, and B would be the acceptor...
.
Mandelic acid is usually prepared by the acid-catalysed hydrolysis of mandelonitrile
Mandelonitrile
Mandelonitrile is a chemical compound of the cyanohydrin class. Small amounts of mandelonitrile occur in the pits of some fruits.-Occurrence:...
, which is the cyanohydrin
Cyanohydrin
A cyanohydrin is a functional group found in organic compounds. Cyanohydrins have the formula R2CCN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids...
of benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...
. Mandelonitrile
Mandelonitrile
Mandelonitrile is a chemical compound of the cyanohydrin class. Small amounts of mandelonitrile occur in the pits of some fruits.-Occurrence:...
can also be prepared by reacting benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...
with sodium bisulfite
Sodium bisulfite
Sodium bisulfite is a chemical compound with the chemical formula NaHSO3. Sodium bisulfite is a food additive with E number E222. This salt of bisulfite can be prepared by bubbling sulfur dioxide in a solution of sodium carbonate in water...
to give the corresponding adduct, forming mandelonitrile
Mandelonitrile
Mandelonitrile is a chemical compound of the cyanohydrin class. Small amounts of mandelonitrile occur in the pits of some fruits.-Occurrence:...
with sodium cyanide
Sodium cyanide
Sodium cyanide is an inorganic compound with the formula NaCN. This highly toxic colorless salt is used mainly in gold mining but has other niche applications...
, which is hydrolyzed
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
:
Alternatively, it arises by base hydrolysis of phenylchloroacetic acid and dibromacetophenone. It also arises by heating phenylglyoxal
Phenylglyoxal
Phenylglyoxal is the organic compound with the formula C6H5CCH. It contains both an aldehyde and a ketone functional group. It is yellow liquid when anhydrous but readily forms a colorless crystalline hydrate...
with alkalis.
Uses
Mandelic acid has a long history of use in the medical community as an antibacterial, particularly in the treatment of urinary tract infections. It has also been used as an oral antibiotic. In skin care, it is also an alternative to glycolic acidGlycolic acid
Glycolic acid is the smallest α-hydroxy acid . This colorless, odorless, and hygroscopic crystalline solid is highly soluble in water. It is used in various skin-care products. Glycolic acid is found in some sugar-crops...
in skin care products. Mandelic acid is also advantageous in that it possesses antibacterial properties. Its use as a skincare modality was pioneered by Dr James E. Fulton, who developed vitamin A acid (tretinoin, Retin A) in 1969. On the basis of this research, dermatologists now suggest mandelic acid for a wide variety of skin concerns, from acne to wrinkles; it is especially good in the treatment of adult acne as it addresses both of these concerns. Mandelic acid products have been used as an alternative treatment for rosacea
Rosacea
Rosacea is a chronic condition characterized by facial erythema . Pimples are sometimes included as part of the definition. Unless it affects the eyes, it is typically a harmless cosmetic condition...
sufferers, as it reduces inflammation and redness. Mandelic acid is also recommended for pre- and post-laser treatment, reducing the amount of redness and irritation caused by laser resurfacing.
The drugs cyclandelate
Cyclandelate
Cyclandelate is a vasodilator used in the treatment of claudication, arteriosclerosis and Raynaud's disease. It is also used to treat nighttime leg cramps, and has been investigated for its effect against migraine. It is orally administered....
and homatropine
Homatropine
Homatropine is an anticholinergic medication that inhibits muscarinic acetylcholine receptors and thus the parasympathetic nervous system...
are ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s of mandelic acid.