Singapore Drugs Database

Indication

Used for nutritional supplementation, also for treating dietary shortage or imbalance.

Mechanism of Action

Many of supplemental L-arginine's activities, including its possible anti-atherogenic actions, may be accounted for by its role as the precursor to nitric oxide or NO. NO is produced by all tissues of the body and plays very important roles in the cardiovascular system, immune system and nervous system. NO is formed from L-arginine via the enzyme nitric oxide synthase or synthetase (NOS), and the effects of NO are mainly mediated by 3,'5' -cyclic guanylate or cyclic GMP. NO activates the enzyme guanylate cyclase, which catalyzes the synthesis of cyclic GMP from guanosine triphosphate or GTP. Cyclic GMP is converted to guanylic acid via the enzyme cyclic GMP phosphodiesterase. NOS is a heme-containing enzyme with some sequences similar to cytochrome P-450 reductase. Several isoforms of NOS exist, two of which are constitutive and one of which is inducible by immunological stimuli. The constitutive NOS found in the vascular endothelium is designated eNOS and that present in the brain, spinal cord and peripheral nervous system is designated nNOS. The form of NOS induced by immunological or inflammatory stimuli is known as iNOS. iNOS may be expressed constitutively in select tissues such as lung epithelium. All the nitric oxide synthases use NADPH (reduced nicotinamide adenine dinucleotide phosphate) and oxygen (O2) as cosubstrates, as well as the cofactors FAD (flavin adenine dinucleotide), FMN (flavin mononucleotide), tetrahydrobiopterin and heme. Interestingly, ascorbic acid appears to enhance NOS activity by increasing intracellular tetrahydrobiopterin. eNOS and nNOS synthesize NO in response to an increased concentration of calcium ions or in some cases in response to calcium-independent stimuli, such as shear stress. In vitro studies of NOS indicate that the Km of the enzyme for L-arginine is in the micromolar range. The concentration of L-arginine in endothelial cells, as well as in other cells, and in plasma is in the millimolar range. What this means is that, under physiological conditions, NOS is saturated with its L-arginine substrate. In other words, L-arginine would not be expected to be rate-limiting for the enzyme, and it would not appear that supraphysiological levels of L-arginine which could occur with oral supplementation of the amino acid^would make any difference with regard to NO production. The reaction would appear to have reached its maximum level. However, in vivo studies have demonstrated that, under certain conditions, e.g. hypercholesterolemia, supplemental L-arginine could enhance endothelial-dependent vasodilation and NO production.

Pharmacokinetics

Absorption

Absorbed from the lumen of the small intestine into the enterocytes. Absorption is efficient and occurs by an active transport mechanism.

Distribution

Metabolism

Some metabolism of L-arginine takes place in the enterocytes. L-arginine not metabolized in the enterocytes enters the portal circulation from whence it is transported to the liver, where again some portion of the amino acid is metabolized.

Elimination

Toxicity

Oral supplementation with L-arginine at doses up to 15 grams daily are generally well tolerated. The most common adverse reactions of higher doses from 15 to 30 grams daily are nausea, abdominal cramps and diarrhea. Some may experience these symptoms at lower doses.

Active Ingredient/Synonyms

(2S)-2-amino-5-(carbamimidamido)pentanoic acid | (2S)-2-amino-5-guanidinopentanoic acid | (S)-2-amino-5-guanidinopentanoic acid | (S)-2-Amino-5-guanidinovaleric acid | Arg | Arginine | L-(+)-Arginine | L-Arg | L-Arginin | R | L-Arginine |

Indication

For the prevention of liver damage and kidney damage associated with overdoses of acetaminophen

Mechanism of Action

Although classified as a non-essential amino acid cysteine may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes. Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available. Due to the ability of thiols to undergo redox reactions, cysteine has antioxidant properties. Cysteine's antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans as well as other organisms. The systemic availability of oral glutathione (GSH) is negligible; so it must be biosynthesized from its constituent amino acids, cysteine, glycine, and glutamic acid. Glutamic acid and glycine are readily available in the diets of most industrialized countries, but the availability of cysteine can be the limiting substrate. Cysteine is also an important source of sulfide in human metabolism. The sulfide in iron-sulfur clusters and in nitrogenase is extracted from cysteine, which is converted to alanine in the process. In a 1994 report released by five top cigarette companies, cysteine is one of the 599 additives to cigarettes. Its use or purpose, however, is unknown, like most cigarette additives. Its inclusion in cigarettes could offer two benefits: Acting as an expectorant, since smoking increases mucus production in the lungs; and increasing the beneficial antioxidant glutathione (which is diminished in smokers).

Active Ingredient/Synonyms

(2R)-2-amino-3-mercaptopropanoic acid | (2R)-2-amino-3-sulfanylpropanoic acid | (R)-2-Amino-3-mercaptopropanoic acid | Cys | Cysteine | Free Cysteine | L-2-Amino-3-mercaptopropionic acid | L-Cys | L-Cystein | L-Zystein | L-Cysteine |

Indication

Supplemental glycine may have antispastic activity. Very early findings suggest it may also have antipsychotic activity as well as antioxidant and anti-inflammatory activities.

Mechanism of Action

In the CNS, there exist strychnine-sensitive glycine binding sites as well as strychnine-insensitive glycine binding sites. The strychnine-insensitive glycine-binding site is located on the NMDA receptor complex. The strychnine-sensitive glycine receptor complex is comprised of a chloride channel and is a member of the ligand-gated ion channel superfamily. The putative antispastic activity of supplemental glycine could be mediated by glycine's binding to strychnine-sensitive binding sites in the spinal cord. This would result in increased chloride conductance and consequent enhancement of inhibitory neurotransmission. The ability of glycine to potentiate NMDA receptor-mediated neurotransmission raised the possibility of its use in the management of neuroleptic-resistant negative symptoms in schizophrenia.
Animal studies indicate that supplemental glycine protects against endotoxin-induced lethality, hypoxia-reperfusion injury after liver transplantation, and D-galactosamine-mediated liver injury. Neutrophils are thought to participate in these pathologic processes via invasion of tissue and releasing such reactive oxygen species as superoxide. In vitro studies have shown that neutrophils contain a glycine-gated chloride channel that can attenuate increases in intracellular calcium and diminsh neutrophil oxidant production. This research is ealy-stage, but suggests that supplementary glycine may turn out to be useful in processes where neutrophil infiltration contributes to toxicity, such as ARDS.

Pharmacokinetics

Absorption

Absorbed from the small intestine via an active transport mechanism.

Distribution

Metabolism

Hepatic

Elimination

Toxicity

ORL-RAT LD₅₀ 7930 mg/kg, SCU-RAT LD₅₀ 5200 mg/kg, IVN-RAT LD₅₀ 2600 mg/kg, ORL-MUS LD₅₀ 4920 mg/kg; Doses of 1 gram daily are very well tolerated. Mild gastrointestinal symptoms are infrequently noted. In one study doses of 90 grams daily were also well tole.

Active Ingredient/Synonyms

Aminoacetic acid | Aminoessigsäure | Aminoethanoic acid | Gly | Glycin | Glycocoll | Glykokoll | Glyzin | Leimzucker | Glycine |

Indication

The actions of supplemental L-histidine are entirely unclear. It may have some immunomodulatory as well as antioxidant activity. L-histidine may be indicated for use in some with rheumatoid arthritis. It is not indicated for treatment of anemia or uremia or for lowering serum cholesterol.

Mechanism of Action

Since the actions of supplemental L-histidine are unclear, any postulated mechanism is entirely speculative. However, some facts are known about L-histidine and some of its metabolites, such as histamine and trans-urocanic acid, which suggest that supplemental L-histidine may one day be shown to have immunomodulatory and/or antioxidant activities. Low free histidine has been found in the serum of some rheumatoid arthritis patients. Serum concentrations of other amino acids have been found to be normal in these patients. L-histidine is an excellent chelating agent for such metals as copper, iron and zinc. Copper and iron participate in a reaction (Fenton reaction) that generates potent reactive oxygen species that could be destructive to tissues, including joints.
L-histidine is the obligate precursor of histamine, which is produced via the decarboxylation of the amino acid. In experimental animals, tissue histamine levels increase as the amount of dietary L-histidine increases. It is likely that this would be the case in humans as well. Histamine is known to possess immunomodulatory and antioxidant activity. Suppressor T cells have H2 receptors, and histamine activates them. Promotion of suppressor T cell activity could be beneficial in rheumatoid arthritis. Further, histamine has been shown to down-regulate the production of reactive oxygen species in phagocytic cells, such as monocytes, by binding to the H2 receptors on these cells. Decreased reactive oxygen species production by phagocytes could play antioxidant, anti-inflammatory and immunomodulatory roles in such diseases as rheumatoid arthritis.
This latter mechanism is the rationale for the use of histamine itself in several clinical trials studying histamine for the treatment of certain types of cancer and viral diseases. In these trials, down-regulation by histamine of reactive oxygen species formation appears to inhibit the suppression of natural killer (NK) cells and cytotoxic T lymphocytes, allowing these cells to be more effective in attacking cancer cells and virally infected cells.

Pharmacokinetics

Absorption

Absorbed from the small intestine via an active transport mechanism requiring the presence of sodium.

Distribution

Metabolism

Elimination

Toxicity

ORL-RAT LD₅₀ > 15000 mg/kg, IPR-RAT LD₅₀ > 8000 mg/kg, ORL-MUS LD₅₀ > 15000 mg/kg, IVN-MUS LD₅₀ > 2000 mg/kg; Mild gastrointestinal side effects.

Active Ingredient/Synonyms

(S)-4-(2-Amino-2-carboxyethyl)imidazole | (S)-a-Amino-1H-imidazole-4-propanoic acid | (S)-alpha-amino-1H-Imidazole-4-propanoic acid | (S)-alpha-Amino-1H-imidazole-4-propionic acid | (S)-α-amino-1H-Imidazole-4-propanoic acid | HIS | Histidina | L-(−)-histidine | L-Histidin | L-Histidine | Histidine |

Indication

The branched-chain amino acids may have antihepatic encephalopathy activity in some. They may also have anticatabolic and antitardive dyskinesia activity.

Mechanism of Action

(Applies to Valine, Leucine and Isoleucine)
This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates.
The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic.
There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.

Pharmacokinetics

Absorption

Absorbed from the small intestine by a sodium-dependent active-transport process

Distribution

Metabolism

Hepatic

Elimination

Toxicity

Symptoms of hypoglycemia, increased mortality in ALS patients taking large doses of BCAAs

Active Ingredient/Synonyms

(2S,3S)-2-Amino-3-methylpentanoic acid | 2-Amino-3-methylvaleric acid | alpha-amino-beta-methylvaleric acid | I | Ile | Isoleucine | L-Isoleucine | α-amino-β-methylvaleric acid | L-Isoleucine |

Indication

There is no support for the claim that aspartates are exercise performance enhancers, i.e. ergogenic aids.

Mechanism of Action

There are also claims that L-aspartate has ergogenic effects, that it enhances performance in both prolonged exercise and short intensive exercise. It is hypothesized that L-aspartate, especially the potassium magnesium aspartate salt, spares stores of muscle glycogen and/or promotes a faster rate of glycogen resynthesis during exercise. It has also been hypothesized that L-aspartate can enhance short intensive exercise by serving as a substrate for energy production in the Krebs cycle and for stimulating the purine nucleotide cycle.

Pharmacokinetics

Absorption

Absorbed from the small intestine by an active transport process

Distribution

Metabolism

Elimination

Toxicity

Mild gastrointestinal side effects including diarrhea. LD₅₀ (rat) > 5,000 mg/kg.

Active Ingredient/Synonyms

(S)-2-aminobutanedioic acid | (S)-2-aminosuccinic acid | 2-Aminosuccinic acid | Asp | Aspartic acid | D | L-Asp | L-Asparaginsaeure | L-Asparaginsäure | L-Aspartate | L-Aspartic acid | L-Aspartic Acid |

Indication

Used for nutritional supplementation, also for treating dietary shortage or imbalance. Used to reduce the acute complications of sickle cell disease in adult and pediatric patients 5 years of age and older [FDA Label].

Mechanism of Action

Supplemental L-glutamine's possible immunomodulatory role may be accounted for in a number of ways. L-glutamine appears to play a major role in protecting the integrity of the gastrointestinal tract and, in particular, the large intestine. During catabolic states, the integrity of the intestinal mucosa may be compromised with consequent increased intestinal permeability and translocation of Gram-negative bacteria from the large intestine into the body. The demand for L-glutamine by the intestine, as well as by cells such as lymphocytes, appears to be much greater than that supplied by skeletal muscle, the major storage tissue for L-glutamine. L-glutamine is the preferred respiratory fuel for enterocytes, colonocytes and lymphocytes. Therefore, supplying supplemental L-glutamine under these conditions may do a number of things. For one, it may reverse the catabolic state by sparing skeletal muscle L-glutamine. It also may inhibit translocation of Gram-negative bacteria from the large intestine. L-glutamine helps maintain secretory IgA, which functions primarily by preventing the attachment of bacteria to mucosal cells. L-glutamine appears to be required to support the proliferation of mitogen-stimulated lymphocytes, as well as the production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). It is also required for the maintenance of lymphokine-activated killer cells (LAK). L-glutamine can enhance phagocytosis by neutrophils and monocytes. It can lead to an increased synthesis of glutathione in the intestine, which may also play a role in maintaining the integrity of the intestinal mucosa by ameliorating oxidative stress. The exact mechanism of the possible immunomodulatory action of supplemental L-glutamine, however, remains unclear. It is conceivable that the major effect of L-glutamine occurs at the level of the intestine. Perhaps enteral L-glutamine acts directly on intestine-associated lymphoid tissue and stimulates overall immune function by that mechanism, without passing beyond the splanchnic bed. The exact mechanism of L-glutamine's effect on NAD redox potential is unknown but is thought to involve increased amounts of reduced glutathione made available by glutamine supplementation [FDA Label]. This improvement in redox potential reduces the amount of oxidative damage which sickle red blood cells are more susceptible to. The reduction in cellular damage is thought to reduce chronic hemolysis and vaso-occlusive events.

Pharmacokinetics

Absorption

Absorption is efficient and occurs by an active transport mechanism. Tmax is 30 minutes after a single dose [FDA Label]. Absorption kinetics following multiple doses has not yet been determined.

Distribution

Volume of distribution is 200 mL/kg after intravenous bolus dose [FDA Label].

Metabolism

Exogenous L-glutamine likely follows the same metabolic pathways as endogenous L-glutamine which is involved in the formation of glutamate, proteins, nucleotides, and amino acid sugars [FDA Label].

Elimination

Toxicity

Doses of L-glutamine up to 21 grams daily appear to be well tolerated. Reported adverse reactions are mainly gastrointestinal and not common. They include constipation and bloating. There is one older report of two hypomanic patients whose manic symptoms were exacerbated following the use of 2 to 4 grams daily of L-glutamine. The symptoms resolved when the L-glutamine was stopped. These patients were not rechallenged, nor are there any other reports of this nature. The most common adverse effects observed in clinical trials of Endari were constipation (21%), nausea (19%), headache (18%), abdominal pain (17%), cough (16%), extremity pain (13%), back pain (12%), and chest pain (12%) [FDA Label].

Active Ingredient/Synonyms

(2S)-2-amino-4-carbamoylbutanoic acid | (2S)-2,5-diamino-5-oxopentanoic acid | (S)-2,5-diamino-5-oxopentanoic acid | Glutamic acid 5-amide | Glutamic acid amide | Glutamine | L-(+)-glutamine | L-2-aminoglutaramic acid | L-glutamic acid γ-amide | L-Glutamin | L-Glutaminsäure-5-amid | Levoglutamide | Q | L-Glutamine |

Indication

Indicated to assist in the prevention of the breakdown of muscle proteins that sometimes occur after trauma or severe stress.

Mechanism of Action

This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates. The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic. There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.

Active Ingredient/Synonyms

(2S)-2-Amino-4-methylpentanoic acid | (2S)-alpha-2-Amino-4-methylvaleric acid | (2S)-alpha-Leucine | (S)-(+)-Leucine | (S)-Leucine | 2-Amino-4-methylvaleric acid | L | L-Leucin | L-Leuzin | Leu | Leucine | L-Leucine |

Indication

Supplemental L-lysine has putative anti-herpes simplex virus activity. There is preliminary research suggesting that it may have some anti-osteoporotic activity.

Mechanism of Action

Proteins of the herpes simplex virus are rich in L-arginine, and tissue culture studies indicate an enhancing effect on viral replication when the amino acid ratio of L-arginine to L-lysine is high in the tissue culture media. When the ratio of L-lysine to L-arginine is high, viral replication and the cytopathogenicity of herpes simplex virus have been found to be inhibited. L-lysine may facilitate the absorption of calcium from the small intestine.

Pharmacokinetics

Absorption

Absorbed from the lumen of the small intestine into the enterocytes by an active transport process

Distribution

Metabolism

Hepatic

Elimination

Active Ingredient/Synonyms

(S)-2,6-diaminohexanoic acid | (S)-lysine | (S)-α,ε-diaminocaproic acid | 6-ammonio-L-norleucine | L-2,6-Diaminocaproic acid | L-lys | L-Lysin | LYS | Lysina | Lysine | Lysine acid | Lysinum | L-Lysine |

Indication

Used for protein synthesis including the formation of SAMe, L-homocysteine, L-cysteine, taurine, and sulfate.

Mechanism of Action

The mechanism of the possible anti-hepatotoxic activity of L-methionine is not entirely clear. It is thought that metabolism of high doses of acetaminophen in the liver lead to decreased levels of hepatic glutathione and increased oxidative stress. L-methionine is a precursor to L-cysteine. L-cysteine itself may have antioxidant activity. L-cysteine is also a precursor to the antioxidant glutathione. Antioxidant activity of L-methionine and metabolites of L-methionine appear to account for its possible anti-hepatotoxic activity. Recent research suggests that methionine itself has free-radical scavenging activity by virtue of its sulfur, as well as its chelating ability.

Pharmacokinetics

Absorption

Absorbed from the lumen of the small intestine into the enterocytes by an active transport process.

Distribution

Metabolism

Hepatic

Elimination

Toxicity

Doses of L-methionine of up to 250 mg daily are generally well tolerated. Higher doses may cause nausea, vomiting and headache. Healthy adults taking 8 grams of L-methionine daily for four days were found to have reduced serum folate levels and leucocytosis. Healthy adults taking 13.9 grams of L-methionine daily for five days were found to have changes in serum pH and potassium and increased urinary calcium excretion. Schizophrenic patients given 10 to 20 grams of L-methionine daily for two weeks developed functional psychoses. Single doses of 8 grams precipitated encephalopathy in patients with cirrhosis.

Active Ingredient/Synonyms

(2S)-2-amino-4-(methylsulfanyl)butanoic acid | (S)-2-amino-4-(methylthio)butanoic acid | (S)-2-amino-4-(methylthio)butyric acid | (S)-methionine | L-(−)-methionine | L-a-Amino-g-methylthiobutyric acid | L-Methionin | L-Methionine | L-α-amino-γ-methylmercaptobutyric acid | M | Met | Methionine |

Indication

L-phenylalanine may be helpful in some with depression. It may also be useful in the treatment of vitiligo. There is some evidence that L-phenylalanine may exacerbate tardive dyskinesia in some schizophrenic patients and in some who have used neuroleptic drugs.

Mechanism of Action

The mechanism of L-phenylalanine's putative antidepressant activity may be accounted for by its precursor role in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.
The mechanism of L-phenylalanine's possible antivitiligo activity is not well understood. It is thought that L-phenylalanine may stimulate the production of melanin in the affected skin

Pharmacokinetics

Absorption

Absorbed from the small intestine by a sodium dependent active transport process.

Distribution

Metabolism

Hepatic. L-phenylalanine that is not metabolized in the liver is distributed via the systemic circulation to the various tissues of the body, where it undergoes metabolic reactions similar to those that take place in the liver.

Elimination

Toxicity

L-phenylalanine will exacerbate symptoms of phenylketonuria if used by phenylketonurics. L-phenylalanine was reported to exacerbate tardive dyskinesia when used by some with schizophrenia.

Active Ingredient/Synonyms

(S)-2-Amino-3-phenylpropionic acid | (S)-alpha-Amino-beta-phenylpropionic acid | 3-phenyl-L-alanine | beta-Phenyl-L-alanine | F | Phe | Phenylalanine | β-phenyl-L-alanine | L-Phenylalanine |

Indication

L-Proline is extremely important for the proper functioning of joints and tendons and also helps maintain and strengthen heart muscles.

Mechanism of Action

Glycogenic, by L-Proline oxidase in the kidney, it is ring-opened and is oxidized to form L-Glutamic acid. L-Ornithine and L-Glutamic acid are converted to L-Proline via L-Glutamic acid-gamma-semialdehyde. It is contained abundantly in collagen, and is intimately involved in the function of arthrosis and chordae.

Active Ingredient/Synonyms

(-)-2-Pyrrolidinecarboxylic acid | (−)-(S)-proline | (−)-2-pyrrolidinecarboxylic acid | (−)-proline | (2S)-pyrrolidine-2-carboxylic acid | (S)-2-Carboxypyrrolidine | (S)-2-Pyrrolidinecarboxylic acid | (S)-pyrrolidine-2-carboxylic acid | 2-Pyrrolidinecarboxylic acid | L-(−)-proline | L-alpha-pyrrolidinecarboxylic acid | L-Prolin | L-pyrrolidine-2-carboxylic acid | L-α-pyrrolidinecarboxylic acid | P | Prolina | Proline | Prolinum | L-Proline |

Indication

Used as a natural moisturizing agent in some cosmetics and skin care products.

Mechanism of Action

L-Serine plays a role in cell growth and development (cellular proliferation). The conversion of L-serine to glycine by serine hydroxymethyltransferase results in the formation of the one-carbon units necessary for the synthesis of the purine bases, adenine and guanine. These bases when linked to the phosphate ester of pentose sugars are essential components of DNA and RNA and the end products of energy producing metabolic pathways, ATP and GTP. In addition, L-serine conversion to glycine via this same enzyme provides the one-carbon units necessary for production of the pyrimidine nucleotide, deoxythymidine monophosphate, also an essential component of DNA.

Active Ingredient/Synonyms

(S)-2-Amino-3-hydroxypropanoic acid | (S)-Serine | alpha-Amino-beta-hydroxypropionic acid | beta-Hydroxyalanine | L-Serine | Ser | Serina | Serinum | Serine |

Indication

The use of diet supplements containing taurine is indicated for the nutritional support of infants and young pediatric patients requiring total parenteral nutrition via central or peripheral routes. The usage of diet supplements containing taurine prevents nitrogen and weight loss or to treat negative nitrogen balance in pediatric patients where the alimentary tract cannot be done through oral, gastrostomy or jejunostomy administration, there is impaired gastrointestinal absorption or protein requirements are substantially increased.[FDA label]

Mechanism of Action

The diet supplements containing taurine function by replacing the missing nutriments in the body. Taurine, as a single agent, presents different functions like substrate for formation of bile salts, cell volume regulation, modulation of intracellular calcium, cytoprotection of central nervous system, etc.[A31398]

Pharmacokinetics

Absorption

Oral administration of taurine was studied and it reported dose-dependent values of AUC, Cmax and tmax wherein a dose of 1-30 mg/kg ranged from 89-3452 mcg min/L, 2-15.7 mcg min/ml and 15 min respectively.[A31399] Further studies in healthy individuals gave an AUC, Cmax and tmax in the range of 116-284.5 mg h/L, 59-112.6 mg/L and 1-2.5 h.[A31400]

Distribution

The distribution of taurine was studied under the two-compartment model and each one of the compartments gave a range for the volume of distribution of 299-353 ml/kg in compartment 1 and 4608-8374 ml/kg in compartment 2 in mice.[A31399] Further studies in healthy indivudals gave a volume of distribution that ranged from 19.8 to 40.7 L.[A31400]

Metabolism

Taurine can be metabolized by diverse organisms to form different types of metabolites derived from the original form of taurine. In the human, the pathways that form the metabolism of taurine are divided in the formation of 5-glutamyl-taurine by the action of the enzyme gamma-glutamyltransferase 6 or the formation of taurocholate by the action of the bile acid-CoA:amino acid N-acyltransferase.[L1060]

Elimination

Clearance

The clearance rate of orally administered taurine was reported to be dose-dependent wherein a dose of 1 mg/kg it presents a clearance rate of 11.7 ml min/kg, 10 mg/kg generates a clearance rate of 18.7 ml min/kg and a dose of 30 mg/kg reports a clearance rate of 9.4 ml min/kg.[A31399] Further studies in healthy individuals generate a clearance rate that ranged from 14 to 34.4 L/h.[A31400]

Toxicity

The administration of taurine has been correlatefd to significant in the hypothalamus and the modification of neuroendocrine functions. Other than that, taurine administration in regular doses is reported by different articles and institutions to be safe.[A31406]

Active Ingredient/Synonyms

Aminoethylsulfonic acid | Taurineold | Taurine |

Indication

L-Threonine makes up collagen, elastin, and enamel protein. It aids proper fat metabolism in the liver, helps the digestive and intestinal tracts function more smoothly, and assists in metabolism and assimilation.

Mechanism of Action

L-Threonine is a precursor to the amino acids glycine and serine. It acts as a lipotropic in controlling fat build-up in the liver. May help combat mental illness and may be very useful in indigestion and intestinal malfunctions. Also, threonine prevents excessive liver fat. Nutrients are more readily absorbed when threonine is present.

Active Ingredient/Synonyms

(2S,3R)-(-)-Threonine | (2S)-threonine | 2-Amino-3-hydroxybutyric acid | L-(-)-Threonine | L-2-Amino-3-hydroxybutyric acid | L-alpha-amino-beta-hydroxybutyric acid | L-Threonin | L-α-amino-β-hydroxybutyric acid | Thr | Threonine | L-Threonine |

Indication

Tryptophan may be useful in increasing serotonin production, promoting healthy sleep, managing depression by enhancing mental and emotional well-being, managing pain tolerance, and managing weight.

Mechanism of Action

A number of important side reactions occur during the catabolism of tryptophan on the pathway to acetoacetate. The first enzyme of the catabolic pathway is an iron porphyrin oxygenase that opens the indole ring. The latter enzyme is highly inducible, its concentration rising almost 10-fold on a diet high in tryptophan. Kynurenine is the first key branch point intermediate in the pathway. Kynurenine undergoes deamniation in a standard transamination reaction yielding kynurenic acid. Kynurenic acid and metabolites have been shown to act as antiexcitotoxics and anticonvulsives. A second side branch reaction produces anthranilic acid plus alanine. Another equivalent of alanine is produced further along the main catabolic pathway, and it is the production of these alanine residues that allows tryptophan to be classified among the glucogenic and ketogenic amino acids. The second important branch point converts kynurenine into 2-amino-3-carboxymuconic semialdehyde, which has two fates. The main flow of carbon elements from this intermediate is to glutarate. An important side reaction in liver is a transamination and several rearrangements to produce limited amounts of nicotinic acid, which leads to production of a small amount of NAD⁺ and NADP⁺.

Toxicity

Oral rat LD₅₀: > 16 gm/kg. Investigated as a tumorigen, mutagen, reproductive effector. Symptoms of overdose include agitation, confusion, diarrhea, fever, overactive reflexes, poor coordination, restlessness, shivering, sweating, talking or acting with excitement you cannot control, trembling or shaking, twitching, and vomiting.

Active Ingredient/Synonyms

(2S)-2-amino-3-(1H-indol-3-yl)propanoic acid | (S)-alpha-Amino-beta-(3-indolyl)-propionic acid | (S)-Tryptophan | (S)-α-amino-1H-indole-3-propanoic acid | L-(-)-Tryptophan | L-(−)-tryptophan | L-β-3-indolylalanine | Trp | Tryptophan | W | L-Tryptophan |

Indication

Promotes mental vigor, muscle coordination, and calm emotions. May also be of use in a minority of patients with hepatic encephalopathy and in some with phenylketonuria.

Mechanism of Action

(Applies to Valine, Leucine and Isoleucine)
This group of essential amino acids are identified as the branched-chain amino acids, BCAAs. Because this arrangement of carbon atoms cannot be made by humans, these amino acids are an essential element in the diet. The catabolism of all three compounds initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation. The catabolism of all three of these amino acids uses the same enzymes in the first two steps. The first step in each case is a transamination using a single BCAA aminotransferase, with a-ketoglutarate as amine acceptor. As a result, three different a-keto acids are produced and are oxidized using a common branched-chain a-keto acid dehydrogenase, yielding the three different CoA derivatives. Subsequently the metabolic pathways diverge, producing many intermediates.
The principal product from valine is propionylCoA, the glucogenic precursor of succinyl-CoA. Isoleucine catabolism terminates with production of acetylCoA and propionylCoA; thus isoleucine is both glucogenic and ketogenic. Leucine gives rise to acetylCoA and acetoacetylCoA, and is thus classified as strictly ketogenic.
There are a number of genetic diseases associated with faulty catabolism of the BCAAs. The most common defect is in the branched-chain a-keto acid dehydrogenase. Since there is only one dehydrogenase enzyme for all three amino acids, all three a-keto acids accumulate and are excreted in the urine. The disease is known as Maple syrup urine disease because of the characteristic odor of the urine in afflicted individuals. Mental retardation in these cases is extensive. Unfortunately, since these are essential amino acids, they cannot be heavily restricted in the diet; ultimately, the life of afflicted individuals is short and development is abnormal The main neurological problems are due to poor formation of myelin in the CNS.

Pharmacokinetics

Absorption

Absorbed from the small intestine by a sodium-dependent active-transport process.

Distribution

Metabolism

Hepatic

Elimination

Toxicity

Symptoms of hypoglycemia, increased mortality in ALS patients taking large doses of BCAAs.

Active Ingredient/Synonyms

(2S)-2-Amino-3-methylbutanoic acid | (S)-Valine | 2-Amino-3-methylbutyric acid | L-(+)-alpha-Aminoisovaleric acid | L-alpha-Amino-beta-methylbutyric acid | Val | Valine | L-Valine |