Skeletal formula of arginine
CAS number  N,  R YesY,  S YesY
PubChem ,  R,  S
ChemSpider  YesY,  R YesY,  S YesY
EC number
IUPHAR ligand
RTECS number CF1934200 S
ATC code B05 S
Beilstein Reference 1725411, 1725412 R, 1725413 S
Gmelin Reference 364938 R
Jmol-3D images Image 1
Image 2
Molecular formula C6H14N4O2
Molar mass 174.20 g mol−1
Appearance White crystals
Odor Odourless
Melting point 260 °C; 500 °F; 533 K
Boiling point 368 °C (694 °F; 641 K)
Solubility in water 14.87 g/100 mL (20 °C)
Solubility slightly soluble in ethanol
insoluble in ethyl ether
log P −1.652
Acidity (pKa) 2.488
Basicity (pKb) 11.509
heat capacity
232.8 J K−1 mol−1 (at 23.7 °C)
Std molar
250.6 J K−1 mol−1
Std enthalpy of
−624.9–−622.3 kJ mol−1
Std enthalpy of
−3.7396–−3.7370 MJ mol−1
MSDS External MSDS
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word WARNING
GHS hazard statements H319
GHS precautionary statements P305+351+338
EU classification Irritant Xi
R-phrases R36
S-phrases S26
LD50 5110 mg/kg (rat, oral)
Related compounds
Related alkanoic acids
Related compounds
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N   YesY/N?)

Arginine (, abbreviated as Arg or R)[1] is an α-amino acid. It was first isolated in 1886.[2] The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that code for arginine during protein synthesis. In mammals, arginine is classified as a semiessential or conditionally essential amino acid, depending on the developmental stage and health status of the individual.[3] Preterm infants are unable to synthesize or create arginine internally, making the amino acid nutritionally essential for them.[4] Arginine was first isolated from a lupin seedling extract in 1886 by the Swiss chemist Ernst Schultze.[5]

In general, most healthy people do not need to supplement with arginine because the body usually produces sufficient amounts.[2]


Dietary sources

Arginine is a conditionally nonessential amino acid, meaning that most of the time it can be manufactured by the human body, and does not need to be obtained directly through the diet. The biosynthetic pathway, however, does not produce sufficient arginine, and some must still be consumed through diet. Individuals with poor nutrition or certain physical conditions may be advised to increase their intake of foods containing arginine. Arginine is found in a wide variety of foods, including:[6]

  • Animal sources
dairy products (e.g., cottage cheese, ricotta, milk, yogurt, whey protein drinks), beef, pork (e.g., bacon, ham), gelatin , poultry (e.g. chicken and turkey light meat), wild game (e.g. pheasant, quail), seafood (e.g., halibut, lobster, salmon, shrimp, snails, tuna)
  • Plant sources
wheat germ and flour, lupins, buckwheat, granola, oatmeal, peanuts, nuts (coconut, pecans, cashews, walnuts, almonds, Brazil nuts, hazelnuts, pinenuts), seeds (pumpkin, sesame, sunflower), chickpeas, cooked soybeans, Phalaris canariensis (canaryseed or alpiste)


Arginine is synthesized from citrulline by the sequential action of the cytosolic enzymes argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL). In terms of energy, this is costly, as the synthesis of each molecule of argininosuccinate requires hydrolysis of adenosine triphosphate (ATP) to adenosine monophosphate (AMP), i.e., two ATP equivalents. In essence, taking an excess of arginine gives more energy by saving ATPs that can be used elsewhere.

Citrulline can be derived from multiple sources:

The pathways linking arginine, glutamine, and proline are bidirectional. Thus, the net utilization or production of these amino acids is highly dependent on cell type and developmental stage.

On a whole-body basis, synthesis of arginine occurs principally via the intestinal–renal axis, wherein epithelial cells of the small intestine, which produce citrulline primarily from glutamine and glutamate, collaborate with the proximal tubule cells of the kidney, which extract citrulline from the circulation and convert it to arginine, which is returned to the circulation. As a consequence, impairment of small bowel or renal function can reduce endogenous arginine synthesis, thereby increasing the dietary requirement.

Synthesis of arginine from citrulline also occurs at a low level in many other cells, and cellular capacity for arginine synthesis can be markedly increased under circumstances that also induce iNOS. Thus, citrulline, a coproduct of the NOS-catalyzed reaction, can be recycled to arginine in a pathway known as the citrulline-NO or arginine-citrulline pathway. This is demonstrated by the fact that, in many cell types, citrulline can substitute for arginine to some degree in supporting NO synthesis. However, recycling is not quantitative because citrulline accumulates along with nitrate and nitrite, the stable end-products of NO, in NO-producing cells.[7]


Arginine plays an important role in cell division, the healing of wounds, removing ammonia from the body, immune function, and the release of hormones.[3][8][9]

The benefits and functions attributed to oral supplementation of L-arginine include:

  • Precursor for the synthesis of nitric oxide (NO)[10] Non-L-arginine derived NO can be generated by the nitrate-nitrite-nitric oxide pathway that is monitored through saliva testing.
  • Reduces healing time of injuries (particularly bone)[8][9]
  • Quickens repair time of damaged tissue[8][9]
  • Helps decrease blood pressure in clinical hypertensive subjects [11][12][13] NO-mediated decrease in blood pressure is influenced by both the L-arginine-dependent nitric oxide synthase pathway and non-L-arginine or alternative pathway through nitrate-rich foods such as beets and spinach.


The distributing basics of the moderate structure found in geometry, charge distribution, and ability to form multiple H-bonds make arginine ideal for binding negatively charged groups. For this reason, arginine prefers to be on the outside of the proteins, where it can interact with the polar environment.

Incorporated in proteins, arginine can also be converted to citrulline by PAD enzymes. In addition, arginine can be methylated by protein methyltransferases.


Arginine is the immediate precursor of nitric oxide (NO), urea, ornithine, and agmatine; is necessary for the synthesis of creatine; and can also be used for the synthesis of polyamines (mainly through ornithine and to a lesser degree through agmatine), citrulline, and glutamate. As a precursor of nitric oxide, arginine may have a role in the treatment of some conditions where vasodilation is required.[3] The presence of asymmetric dimethylarginine (ADMA), a close relative, inhibits the nitric oxide reaction; therefore, ADMA is considered a marker for vascular disease, just as L-arginine is considered a sign of a healthy endothelium.

Treatment of dentin hypersensitivity

Arginine (8%) in dental products (e.g., toothpaste) provides effective relief from sensitive teeth by depositing a dentin-like mineral, containing calcium and phosphate, within the dentin tubules and in a protective layer on the dentin surface.[14]

Treatment of herpes simplex virus

An unproven claim is that a low ratio of arginine to lysine may be of benefit in the treatment of herpes simplex virus. For more information, refer to Herpes - Treatment also see journal article.[15]

Possible increased risk of death after supplementation following heart attack

A clinical trial found that patients taking an L-arginine supplement following a heart attack found no change in the heart's vascular tone or decrease in the symptoms of congestive heart failure (the heart's ability to pump). In fact, six more patients that were taking L-arginine died than those taking a placebo, resulting in early termination of the study with the recommendation that the supplement not be used by heart attack patients.[16][17]


Delocalization of charge in guanidinium group of L-Arginine

The amino acid side-chain of arginine consists of a 3-carbon aliphatic straight chain, the distal end of which is capped by a complex guanidinium group.

With a pKa of 12.48, the guanidinium group is positively charged in neutral, acidic, and even most basic environments, and thus imparts basic chemical properties to arginine. Because of the conjugation between the double bond and the nitrogen lone pairs, the positive charge is delocalized, enabling the formation of multiple H-bonds.


Growth hormone

Intravenously-administered arginine stimulates the secretion of growth hormone,[18] and is used in growth hormone stimulation tests.[19] Two studies have found that oral arginine supplementation is also effective at increasing resting GH levels. The first study found that oral preparations of arginine are effective at increasing growth hormone levels. In fact, the 9-gram dose resulted in mean peak GH levels of 6.4 (+/- 1.3) µg/L versus placebo levels of 2.9 (+/- 0.7).[20] Another study found similar results. It included resting versus exercise and oral L-arginine versus oral placebo. The authors concluded that "Oral arginine alone (7 g) stimulated GH release, but a greater GH response was seen with exercise alone. The combined effect of arginine before exercise attenuates the GH response… GH production: Ex > Arg+Ex > Arg > placebo" suggesting against supplementing with arginine alone prior to exercise if the goal is to raise GH levels, but concurring with the previous study that oral L-arginine increases GH on days free of significant exercise.[20] In contrast to these two studies that found increased resting GH due to oral arginine supplementation, a third study did not find increase in resting GH levels from oral supplementation. In that study, oral preparations of L-arginine were ineffective at increasing growth hormone levels despite being effective at increasing plasma levels of L-arginine.[21]

MELAS syndrome

Several trials delved into effects of L-arginine in MELAS syndrome, a mitochondrial disease.[22]

High blood pressure

Intravenous infusion of arginine reduces blood pressure in patients with hypertension as well as normal subjects.[23]

A meta-analysis showed that L-arginine reduces blood pressure with pooled estimates of 5.4/2.7 mmHg for SBP/DBP.[13]

Supplementation with L-arginine reduces diastolic blood pressure and lengthens pregnancy for women with gestational hypertension, including women with high blood pressure as part of pre-eclampsia.[24] It does not lower systolic blood pressure or improve the baby's weight at birth.

See also


  1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature. "Nomenclature and Symbolism for Amino Acids and Peptides". Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. Archived from the original on 29 May 2007. Retrieved 2007-05-17. 
  2. ^ a b Mayo Clinic
  3. ^ a b c Tapiero, H.; et al. (November 2002). "L-Arginine". Biomedicine and Pharmacotherapy 56 (9): 439–445 REVIEW.  
  4. ^ Wu, G.; et al. (August 2004). "Arginine deficiency in preterm infants: biochemical mechanisms and nutritional implications". Journal of Nutritional Biochemistry 15 (8): 332–451 REVIEW.  
  5. ^ Watson, Ronald Ross (2012). Bioactive Dietary Factors and Plant Extracts in Dermatology.  
  6. ^ "L-Arginine Supplements Nitric Oxide Scientific Studies Food Sources". Retrieved 2007-02-20. 
  7. ^ Morris Jr, SM (October 2004). "Enzymes of arginine metabolism.". The Journal of nutrition 134 (10 Suppl): 2743S–2747S.  
  8. ^ a b c Stechmiller, J.K.; et al. (February 2005). "Arginine supplementation and wound healing". Nutrition in Clinical Practice 20 (13): 52–61 REVIEW.  
  9. ^ a b c Witte, M.B.; Barbul, A (Nov–Dec 2003). "Arginine physiology and its implication for wound healing". Wound Repair and Regeneration 11 (6): 419–423 REVIEW.  
  10. ^ Andrew, P.J.; Myer, B. (August 15, 1999). "Enzymatic function of nitric oxide synthases". Cardiovascular Research 43 (3): 521–531 REVIEW.   [1]
  11. ^ Gokce, N.. (October 2004). "L-Arginine and hypertension". Journal of Nutrition 134 (10 Suppl): 2807S–2811S REVIEW.  
  12. ^ Rajapakse, N.W.; et al. (December 2008). "Exogenous L-arginine ameliorates angiotensin II-induced hypertension and renal damage in rats". Hypertension 52 (6): 1084–1090.   [2]
  13. ^ a b Dong JY, Qin LQ, Zhang Z, Zhao Y, Wang J, Arigoni F, Zhang W. (2011). "Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials". American Heart Journal 162 (6): 959–965.  
  14. ^ Petrou, I.; et al. (2009). "A breakthrough therapy for dentin hypersensitivity: how dental products containing 8% arginine and calcium carbonate work to deliver effective relief of sensitive teeth.". The Journal of Clinical Dentisry 20 (1): 23–31.  
  15. ^ Takeshi Naito, Hiroshi Irie, Kazuko Tsujimoto, Keiko Ikeda, Tsutomu Arakawa, A. Hajime Koyama (April 2009). "Antiviral effect of arginine against herpes simplex virus type 1". International Journal of Molecular Medicine (International Journal of Molecular Medicine) 23 (4): 495–499.  
  16. ^ Medical College of Georgia. "Diabetes Makes It Hard For Blood Vessels To Relax." ScienceDaily 1 February 2008. 1 February 2008
  17. ^ Schulman, SP, Becker, LC, Kass, DA, Champion, HC, Terrin, ML, Forman, S, Ernst, KV, Kelemen, MD, Townsend, SN, Capriotti, A, Hare, JM, Gerstenblith, G (January 2006). "L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial.". JAMA: the Journal of the American Medical Association 295 (1): 58–64.  
  18. ^ Alba-Roth J, Müller O, Schopohl J, von Werder K (1988). "Arginine stimulates growth hormone secretion by suppressing endogenous somatostatin secretion". J Clin Endocrinol Metab 67 (6): 1186–9.  
  19. ^ U.S. National Library of Medicine (September 2009Growth hormone stimulation test
  20. ^ a b Collier, S. R.; Casey, D. P.; Kanaley, J. A. (2005). "Growth hormone responses to varying doses of oral arginine". Growth Hormone & IGF Research 15 (2): 136–139.  
  21. ^ Forbes, SC; Bell, GJ (June 2011). "The acute effects of a low and high dose of oral L-arginine supplementation in young active males at rest.". Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme 36 (3): 405–11.  
  22. ^ Finsterer J (November 2009). "Management of mitochondrial stroke-like-episodes".  
  23. ^ Nakaki, T., Hishikawa, K., Suzuki, H., Saruta, T., Kato, R.; Hishikawa; Suzuki; Saruta; Kato (1990). "L-arginine-induced hypotension". Lancet 336 (8716): 696.  
  24. ^ Gui, Shunping; Jia, Jin; Niu, Xiaoyu; Bai, Yi (Mar 2014). "Arginine supplementation for improving maternal and neonatal outcomes in hypertensive disorder of pregnancy: a systematic review". Journal of the renin-angiotensin-aldosterone system: JRAAS 15 (1): 88–96.  

External links

  • NIST Chemistry Webbook
  • Mayo Clinic discussion of Arginine.
  • National Institute of Health discussion of Arginine.