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Other names 6,7-Dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline | |
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3D model (JSmol) | |
ChEBI | |
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KEGG | |
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Properties | |
C10H13NO2 | |
Molar mass | 179.219 g·mol−1 |
Melting point | 147–149 °C (297–300 °F; 420–422 K) [1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Salsolinol is a chemical compound derived from dopamine which plays a role in neurotransmission and is neurotoxic.
It has been linked to dopamine-related disorders including Parkinson's disease and alcohol use disorder. It is both synthesized in the human body and ingested in several common dietary sources. [2]
Salsolinol is a catechol isoquinoline which is a yellow solid at room temperature. [1] Salsolinol, as a chiral molecule, comes in two enantiomers: (R)-salsolinol and (S)-salsolinol. The two may have different biological effects.
The racemate can be synthesized via a Pictet-Spengler reaction. [3] A chemoenzymatic, enantioselective synthesis of the (R)-enantiomer has also been reported. [4] Salsolinol has been used as a starting material to prepare some tetrahydroisoquinoline-based prospective drugs. [5] [6]
Salsolinol is found in several edible plants, most prominently bananas and cocoa products as well as beer. [7] [8] [9] Other plants, including black cohosh, which is used in many herbal remedies, also contain salsolinol. [10]
Salsolinol is endogenously synthesized by multiple routes, although its origin in the human body remains controversial. There are two main routes for its production: one which is through a non-enantiospecific Pictet-Spengler reaction of dopamine and acetaldehyde, and one which is mediated by the enzyme salsolinol synthase. [11]
Salsolinol synthase exclusively produces the (R)-enantiomer of salsolinol.
It has been speculated that salsolinol may also arise from salsolinol-1-carboxylic acid, which is formed by the reaction of dopamine and pyruvic acid. This transformation would occur via a proposed enzymatic pathway that has not been elucidated yet. [11]
Salsolinol is metabolized by an N-methyltransferase enzyme into N-methyl-(R)-salsolinol. This can then be converted by an amine oxidase into 1,2-dimethyl-6,7-dihydroxyisoquinolinium (DMDHIQ+). It can also be methylated to form its 7-methoxy and 6-methoxy versions by the enzyme catechol-O-methyltransferase (COMT). [12] [11]
Salsolinol binds to several receptors associated with dopaminergic pathways. [2] [13] It may be an agonist of the μ-opioid receptor and of dopaminergic D1 and D3 receptors. [2]
Salsolinol itself also appears to be neurotoxic, the mechanism of which is not clear. Its metabolites, including N-methyl-(R)-salsolinol, also exhibit neurotoxic effects.
Salsolinol has been shown to be involved in the secretion of prolactin in the pituitary gland in lactating rats and lactating sheep. [14] [15] Administration of a solution of salsolinol was not shown to raise prolactin levels in human women. [16]
Salsolinol is detectable in the cerebrospinal fluid of Parkinson's disease (PD) patients and is involved in the pathogenesis of PD. [17] It is known to exercise inhibitory effects on tyrosine hydroxylase [18] and to be toxic to dopaminergic neurons. [19] A mechanism for the induction of Parkinson's by salsolinol is linked to its mediation of pyroptosis. [20]
The connection between salsolinol and alcohol intake remains controversial. An early hypothesis was that the synthesis of salsolinol in the human body was caused by ethanol consumption, because it was being made from dopamine and acetaldehyde (a metabolite of ethanol). Several studies in the 1970s and 80s would seem to corroborate this link. However, no consistent connection between ethanol intake and salsolinol levels were conclusively established. As of the 2020s, it is understood that the primary contributor to levels of salsolinol in blood plasma is dietary intake, not acute ethanol consumption. [21] Part of the challenge in studying this is that salsolinol also is produced endogenously, and in all cases its levels are very low, making it difficult to detect and quantify with precision. [22]
Further confounding the issue, there is evidence that salsolinol may be implicated in alcohol use disorder and may play a role in increasing cravings for ethanol. (R)-Salsolinol stereospecifically induces behavioral sensitization and leads to excessive alcohol intake in rats. [23]
Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia, rigidity, and postural instability. Both hypokinetic as well as hyperkinetic features are displayed by Parkinsonism. These are the four motor symptoms found in Parkinson's disease (PD) – after which it is named – dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD), and many other conditions. This set of symptoms occurs in a wide range of conditions and may have many causes, including neurodegenerative conditions, drugs, toxins, metabolic diseases, and neurological conditions other than PD.
Disulfiram is a medication used to support the treatment of chronic alcoholism by producing an acute sensitivity to ethanol. Disulfiram works by inhibiting the enzyme aldehyde dehydrogenase, causing many of the effects of a hangover to be felt immediately following alcohol consumption. Disulfiram plus alcohol, even small amounts, produces flushing, throbbing in the head and neck, a throbbing headache, respiratory difficulty, nausea, copious vomiting, sweating, thirst, chest pain, palpitation, dyspnea, hyperventilation, fast heart rate, low blood pressure, fainting, marked uneasiness, weakness, vertigo, blurred vision, and confusion. In severe reactions there may be respiratory depression, cardiovascular collapse, abnormal heart rhythms, heart attack, acute congestive heart failure, unconsciousness, convulsions, and death.
Hyperprolactinaemia is a condition characterized by abnormally high levels of prolactin in the blood. In women, normal prolactin levels average to about 13 ng/mL, while in men, they average 5 ng/mL. The upper normal limit of serum prolactin is typically between 15 to 25 ng/mL for both genders. Levels exceeding this range indicate hyperprolactinemia.
Dopaminergic pathways in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.
Domperidone, sold under the brand name Motilium among others, is a dopamine antagonist medication which is used to treat nausea and vomiting and certain gastrointestinal problems like gastroparesis. It raises the level of prolactin in the human body and is used off label to induce and promote breast milk production. It may be taken by mouth or rectally.
Nomifensine (Merital, Alival) is a norepinephrine-dopamine reuptake inhibitor, i.e. a drug that increases the amount of synaptic norepinephrine and dopamine available to receptors by blocking the dopamine and norepinephrine reuptake transporters. This is a mechanism of action shared by some recreational drugs like cocaine and the medication tametraline (see DRI). Research showed that the (S)-isomer is responsible for activity.
A dopamine agonist is a compound that activates dopamine receptors. There are two families of dopamine receptors, D1-like and D2-like. They are all G protein-coupled receptors. D1- and D5-receptors belong to the D1-like family and the D2-like family includes D2, D3 and D4 receptors. Dopamine agonists are primarily used in the treatment of the motor symptoms of Parkinson's disease, and to a lesser extent, in hyperprolactinemia and restless legs syndrome. They are also used off-label in the treatment of clinical depression. Impulse control disorders are associated with the use of dopamine agonists for whatever condition.
Aporphine is an alkaloid with the chemical formula C17H17N. It is the core chemical substructure of the aporphine alkaloids, a subclass of quinoline alkaloids. It can exist in either of two enantiomeric forms, (R)-aporphine and (S)-aporphine.
The nuclear receptor 4A2 (NR4A2) also known as nuclear receptor related 1 protein (NURR1) is a protein that in humans is encoded by the NR4A2 gene. NR4A2 is a member of the nuclear receptor family of intracellular transcription factors.
Dopamine receptor D2, also known as D2R, is a protein that, in humans, is encoded by the DRD2 gene. After work from Paul Greengard's lab had suggested that dopamine receptors were the site of action of antipsychotic drugs, several groups, including those of Solomon H. Snyder and Philip Seeman used a radiolabeled antipsychotic drug to identify what is now known as the dopamine D2 receptor. The dopamine D2 receptor is the main receptor for most antipsychotic drugs. The structure of DRD2 in complex with the atypical antipsychotic risperidone has been determined.
Tetrahydroisoquinoline (TIQ or THIQ) is an organic compound with the chemical formula C9H11N. Classified as a secondary amine, it is derived from isoquinoline by hydrogenation. It is a colorless viscous liquid that is miscible with most organic solvents. The tetrahydroisoquinoline skeleton is encountered in a number of bioactive compounds and drugs.
GBR-12935 is a piperazine derivative which is a potent and selective dopamine reuptake inhibitor. It was originally developed in its 3H radiolabelled form for the purpose of mapping the distribution of dopaminergic neurons in the brain by selective labelling of dopamine transporter proteins. This has led to potential clinical uses in the diagnosis of Parkinson's disease, although selective radioligands such as Ioflupane (123I) are now available for this application. GBR-12935 is now widely used in animal research into Parkinson's disease and the dopamine pathways in the brain.
A monoamine releasing agent (MRA), or simply monoamine releaser, is a drug that induces the release of a monoamine neurotransmitter from the presynaptic neuron into the synapse, leading to an increase in the extracellular concentrations of the neurotransmitter. Many drugs induce their effects in the body and/or brain via the release of monoamine neurotransmitters, e.g., trace amines, many substituted amphetamines, and related compounds.
Norsalsolinol is a chemical compound that is produced naturally in the body through the metabolism of dopamine. It has been shown to be a selective dopaminergic neurotoxin, and has been suggested as a possible cause of neurodegenerative conditions such as Parkinson's disease and the brain damage associated with alcoholism, although evidence for a causal relationship is unclear.
JNJ-7925476 is a triple reuptake inhibitor antidepressant discovered by Johnson & Johnson, but never marketed.
OSU-6162 (PNU-96391) is a compound which acts as a partial agonist at both dopamine D2 receptors and 5-HT2A receptors. It acts as a dopamine stabilizer in a similar manner to the closely related drug pridopidine, and has antipsychotic, anti-addictive and anti-Parkinsonian effects in animal studies. Both enantiomers show similar activity but with different ratios of effects, with the (S) enantiomer (–)-OSU-6162 that is more commonly used in research, having higher binding affinity to D2 but is a weaker partial agonist at 5-HT2A, while the (R) enantiomer (+)-OSU-6162 has higher efficacy at 5-HT2A but lower D2 affinity.
Salsoline is a tetrahydroisoquinoline alkaloid found in some plants of the genus Salsola. Salsoline is the monomethylated metabolite of salsolinol which has been thought to contribute to Parkinson's disease. Also, this has been tied to the neuropathology of chronic alcoholism.
A prolactin modulator is a drug which affects the hypothalamic–pituitary–prolactin axis by modulating the secretion of the pituitary hormone prolactin from the anterior pituitary gland. Prolactin inhibitors suppress and prolactin releasers induce the secretion of prolactin, respectively.
Mevidalen is a dopaminergic drug which is under development for the treatment of Lewy body disease, including those with Parkinson's disease.
A monoamine neurotoxin, or monoaminergic neurotoxin, is a drug that selectively damages or destroys monoaminergic neurons. Monoaminergic neurons are neurons that signal via stimulation by monoamine neurotransmitters including serotonin, dopamine, and norepinephrine. Examples of monoamine neurotoxins include the serotonergic neurotoxins para-chloroamphetamine (PCA), methylenedioxymethamphetamine (MDMA), and 5,7-dihydroxytryptamine (5,7-DHT); the dopaminergic neurotoxins oxidopamine (6-hydroxydopamine), MPTP, and methamphetamine; and the noradrenergic neurotoxins oxidopamine and DSP-4. Dopaminergic neurotoxins can induce a Parkinson's disease-like condition in animals and humans. Serotonergic neurotoxins have been associated with cognitive and memory deficits and psychiatric changes.