Eudysmic ratio
Encyclopedia
The Eudysmic ratio is a common term in pharmacology
, chemistry
, and molecular biology
. The eudysmic ratio describes the difference in pharmacologic activity
between the two enantiomers of a drug.
Any time there is a chiral
carbon in an organic
molecule, the plane of symmetry is broken and a pair of enantiomer
s exist - molecules that are essentially "mirror images" of each other. An oft-used example is that of a person's hands; each hand has the same five fingers attached to the palm in the same pattern, and the left hand is the mirror image of the right hand. There is no other way besides "Right hand" and "Left hand" that one can attach the fingers to the palm and still have a true hand. This example is very similar to how one would describe enantiomers.
When enantiomers are formed non selectively and the resulting product contains an equal quantity of each enantiomer then it is called a racemic
mixture.
In pharmacology it is frequently, though not always, the case that one enantiomer of a chiral drug has greater pharmacological activity than the other. The eudysmic ratio is a mathematical equation that quantitatively measures the difference in this activity. A eudysmic ratio significantly differing from 1 means that there is a large difference in activity between the two enantiomers.
The more active enantiomer is called the eutomer
, whereas the less active isomer is called the distomer
. One way the eudysmic ratio is computed is by dividing the EC50
or the IC50
of the distomer by the EC50 or the IC50 of the eutomer. Whether one chooses to use the EC50 or IC50 depends on the drug in question.
Citalopram
is a case example of such a compound, and steps were taken to separate out the weaker enantiomer.
Thalidomide
is a drug whose two enantiomers cause distinctly different effects from one another. This is an example where the two enantiomers of a drug have different pharmacologic effects.
Amino acid
s are also a very interesting example with an extremely high eudysmic rato. Nearly all of the amino acids in the human body are called "L" amino acids; despite being chiral, the body almost exclusively creates and uses amino acids in this one configuration. D amino acids, the enantiomers - or "mirror images" - of the amino acids in the human body have no activity and cannot be incorporated into proteins. D-Aspartate and D-Serine are two notable counterexamples, but they do not appear to ever be incorporated into proteins, and instead act individually as signalling molecules.
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
, chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, and molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
. The eudysmic ratio describes the difference in pharmacologic activity
Biological activity
In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other...
between the two enantiomers of a drug.
Any time there is a 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....
carbon in an organic
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
molecule, the plane of symmetry is broken and a pair of enantiomer
Enantiomer
In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable , much as one's left and right hands are the same except for opposite orientation. It can be clearly understood if you try to place your hands one over the other without...
s exist - molecules that are essentially "mirror images" of each other. An oft-used example is that of a person's hands; each hand has the same five fingers attached to the palm in the same pattern, and the left hand is the mirror image of the right hand. There is no other way besides "Right hand" and "Left hand" that one can attach the fingers to the palm and still have a true hand. This example is very similar to how one would describe enantiomers.
When enantiomers are formed non selectively and the resulting product contains an equal quantity of each enantiomer then it is called a 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.
In pharmacology it is frequently, though not always, the case that one enantiomer of a chiral drug has greater pharmacological activity than the other. The eudysmic ratio is a mathematical equation that quantitatively measures the difference in this activity. A eudysmic ratio significantly differing from 1 means that there is a large difference in activity between the two enantiomers.
The more active enantiomer is called the eutomer
Eutomer
The eutomer is the molecular chiral enantiomer having the desired bioactivity, e. g. as as an active ingredient in a drug. On the other hand the enantiomer of the eutomer having the undesired bioactivity is called distomer....
, whereas the less active isomer is called the distomer
Distomer
The distomer is an enantiomer in an optically active compound. It is often the case that only a single one of the enantiomers contains all of the wanted bioactivity, the distomer is often less active, has no disired activity or may even be toxic....
. One way the eudysmic ratio is computed is by dividing the EC50
EC50
The term half maximal effective concentration refers to the concentration of a drug, antibody or toxicant which induces a response halfway between the baseline and maximum after some specified exposure time...
or the IC50
IC50
The half maximal inhibitory concentration is a measure of the effectiveness of a compound in inhibiting biological or biochemical function. This quantitative measure indicates how much of a particular drug or other substance is needed to inhibit a given biological process by half...
of the distomer by the EC50 or the IC50 of the eutomer. Whether one chooses to use the EC50 or IC50 depends on the drug in question.
Citalopram
Citalopram
Citalopram brand names: Celexa, Cipramil) is an antidepressant drug of the selective serotonin reuptake inhibitor class. It has U.S...
is a case example of such a compound, and steps were taken to separate out the weaker enantiomer.
Thalidomide
Thalidomide
Thalidomide was introduced as a sedative drug in the late 1950s that was typically used to cure morning sickness. In 1961, it was withdrawn due to teratogenicity and neuropathy. There is now a growing clinical interest in thalidomide, and it is introduced as an immunomodulatory agent used...
is a drug whose two enantiomers cause distinctly different effects from one another. This is an example where the two enantiomers of a drug have different pharmacologic effects.
Amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s are also a very interesting example with an extremely high eudysmic rato. Nearly all of the amino acids in the human body are called "L" amino acids; despite being chiral, the body almost exclusively creates and uses amino acids in this one configuration. D amino acids, the enantiomers - or "mirror images" - of the amino acids in the human body have no activity and cannot be incorporated into proteins. D-Aspartate and D-Serine are two notable counterexamples, but they do not appear to ever be incorporated into proteins, and instead act individually as signalling molecules.