Serotonin, also known as 5-hydroxytryptamine, is a monoamine neurotransmitter with a wide range of functions in both the central nervous system and also peripheral tissues. It is involved in mood, cognition, reward, learning, memory, and physiological pro processes. At the biochemical level serotonin is synthesized from L-tryptophan by tryptophan hydroxylase to form 5-hydroxytryptophan followed by decarboxylation via aromatic L-amino acid decarboxylase. Synaptic signaling is mediated through multiple receptor families designated 5-HT1 through 5-HT7, which include G protein coupled receptors and the ionotropic 5-HT3 receptor, and signaling is terminated by reuptake via the serotonin transporter SERT and by monoamine oxidase A dependent metabolism to 5-hydroxyindoleacetic acid 5-HIAA. Serotonin is stored in synaptic vesicles through vesicular monoamine transporter VMAT in neurons and in dense granules in platelets peripherally, and it contributes to gastrointestinal motility, platelet function, vascular tone, and metabolic regulation. The molecule has formula C10H12N2O and molecular weight 176.22 g mol, a primary amine with a pKa near 10, limited passive blood brain barrier permeability requiring in situ neuronal synthesis for central pools, and it is routinely quantified by validated analytical methods such as HPLC coupled to UV or mass spectrometric detection.
Parent: Serotonin
Parent: Serotonin
Parent: Serotonin
Parent: Serotonin
Parent: Serotonin
Parent: Serotonin
Parent: Serotonin / Tryptamine
Parent: Serotonin / Melatonin
Parent: Serotonin
Parent: Serotonin / Tryptamine
Parent: Serotonin / Melatonin
High purity research and pharmaceutical grade serotonin preparations are typically specified with HPLC purities greater than 98 percent and total related substances controlled below 1 to 2 percent depending on product grade and regulatory requirements, while individual related-compound limits are commonly set below 0.1 to 0.5 percent. Common related compounds and impurities detected by LC MS or NMR include the metabolite 5-hydroxyindoleacetic acid 5-HIAA, N-acetylserotonin, tryptamine, 5-methoxytryptamine, residual L-tryptophan, and partially decarboxylated intermediates such as 5-hydroxytryptophan; oxidative byproducts including indole quinones can appear under suboptimal storage or synthesis conditions. Impurity profiles depend on synthetic route and storage stability, and as a result manufacturers control and monitor impurity amounts through purification, antioxidant protection, light exclusion, and validated analytical impurity assays during release and stability testing.
Reduced serotonin availability can result from insufficient precursor supply especially low dietary tryptophan, impaired enzymatic synthesis due to tryptophan hydroxylase dysfunction or genetic variants, increased catabolism via elevated monoamine oxidase A activity, chronic stress and elevated cortisol, proinflammatory cytokine activity that diverts tryptophan to the kynurenine pathway, and altered transporter or vesicular storage function. Certain medications and chronic substance use can also lower central or peripheral serotonin pools.
Strategies to increase serotonin include interventions that raise precursor availability or reduce reuptake or metabolism such as dietary sources of tryptophan or controlled 5-hydroxytryptophan supplementation, regular aerobic exercise, bright light therapy for circadian modulation, pharmacological agents like selective serotonin reuptake inhibitors or monoamine oxidase inhibitors under medical supervision, and interventions that reduce inflammation or normalize gut microbiota which can influence peripheral serotonin synthesis and central availability.
Elevated serotonergic activity can produce symptoms of agitation and increased anxiety in some individuals, and excessive serotonin activity can lead to serotonin syndrome which includes autonomic instability, neuromuscular hyperactivity, and altered mental status in severe cases. Initial treatment with serotonergic drugs can transiently increase anxiety for some patients, so careful dose management and medical oversight are important.
Factors that reduce serotonin include chronic stress, sleep deprivation, systemic inflammation that shifts tryptophan metabolism to kynurenine, diets deficient in tryptophan, certain medications that deplete monoamines or interfere with synthesis, excessive alcohol use, and specific genetic polymorphisms affecting synthesis enzymes or the serotonin transporter. Storage or degradation issues and oxidative instability during manufacture or storage can also lower available serotonin in preparations.
