Title: Synephrine
CAS Registry Number: 94-07-5
CAS Name: 4-Hydroxy-a-[(methylamino)methyl]benzenemethanol
Additional Names: p-hydroxy-a-[(methylamino)methyl]benzyl alcohol; 1-(4-hydroxyphenyl)-2-methylaminoethanol; p-methylaminoethanolphenol; b-methylamino-a-(4-hydroxyphenyl)ethyl alcohol; methylaminomethyl 4-hydroxyphenyl carbinol
Trademarks: Analeptin; Ethaphene; Oxedrine; Parasympatol; Simpalon; Synephrin (Neukonigsforder); Synthenate
Molecular Formula: C9H13NO2
Molecular Weight: 167.21
Percent Composition: C 64.65%, H 7.84%, N 8.38%, O 19.14%
Literature References: Prepd by hydrogenating w-methylamino-4-hydroxyacetophenone in water in the presence of Pt or Pd: DE 566578 (1931 to Boehringer, Ing.), Frdl. 18, 3025.
Properties: Crystals, mp 184-185°. Stable to air and light.
Melting point: mp 184-185°
Derivative Type: Hydrochloride
CAS Registry Number: 5985-28-4
Molecular Formula: C9H13NO2.HCl
Molecular Weight: 203.67
Percent Composition: C 53.07%, H 6.93%, N 6.88%, O 15.71%, Cl 17.41%
Properties: Crystals, mp 151-152°. Freely sol in water.
Melting point: mp 151-152°
Derivative Type: Tartrate
CAS Registry Number: 16589-24-5
Trademarks: Corvasymton; Simpadren; Sympathol
Molecular Formula: 2C9H13NO2.C4H6O6
Molecular Weight: 484.50
Percent Composition: C 54.54%, H 6.66%, N 5.78%, O 33.02%
Properties: Crystals, mp 188-190° (some dec). Freely sol in water; sol in alcohol.
Melting point: mp 188-190° (some dec)
Derivative Type: Tartaric acid monoester
CAS Registry Number: 6414-49-9
Additional Names: p-Methylaminoethanolphenol tartrate
Trademarks: Neupentedrin; Pentedrin
Molecular Formula: C13H17NO7
Molecular Weight: 299.28
Percent Composition: C 52.17%, H 5.73%, N 4.68%, O 37.42%
Therap-Cat: Adrenergic; vasopressor.
Keywords: a-Adrenergic Agonist; Antihypotensive.
Synhexyl Synsorbs Syringaldehyde Syringin Syrosingopine

CAS number 94-07-5 YesY
PubChem 7172
ChemSpider 6904 YesY
KEGG D07148 YesY
ChEBI CHEBI:29081 YesY
ATC code C01CA08,S01GA06, QS01FB90
Jmol-3D images Image 1
Molecular formula C9H13NO2
Molar mass 167.21 g/mol
Appearance colorless solid
Melting point 162-164°C (R-(-)-enantiomer); 184-185°C (racemate)
Solubility in water soluble
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

This article will focus, insofar as possible, on synephrine itself, rather than on the drug mixtures containing it.

Synephrine, or, more specifically, p-synephrine, is an alkaloid, occurring naturally in some plants and animals, as well as in approved drugs products in form of its m-substituted analog known as neo-synephrine.[1] p-synephrine (or formerly Sympatol and oxedrine [BAN]) and m-synephrine are known for their longer acting adrenergic effects compared to norepinephrine. This substance is present at very low concentrations in common foodstuffs such as orange juice and other orange (Citrus species) products, both of the "sweet" and "bitter" variety. The preparations used in Traditional Chinese Medicine (TCM), also known as Zhi Shi, are the immature and dried whole oranges from Citrus aurantium (Fructus Aurantii Immaturus). Extracts of the same material or purified synephrine are also marketed in the US, sometimes in combination with caffeine, as a weight-loss-promoting dietary supplement for oral consumption. While the traditional preparations have been in use for millennia as a component of TCM-formulas, synephrine itself is not an approved OTC drug. As a pharmaceutical, m-synephrine is still used as a sympathomimetic (i.e. for its hypertensive and vasoconstrictor properties), mostly by injection for the treatment of emergencies such as shock, and rarely orally for the treatment of bronchial problems associated with asthma and hay-fever.[a]

It is important to distinguish between studies concerning synephrine as a single chemical entity (and even here it should be borne in mind that synephrine can exist in the form of either of two stereoisomers, d- and l-synephrine, which are chemically and pharmacologically distinct), and synephrine which is mixed with other drugs and/or botanical extracts in a "Supplement", as well as synephrine which is present as only one chemical component in a naturally-occurring mixture of phytochemicals such as the rind or fruit of a bitter orange. Mixtures containing synephrine as only one of their chemical components (regardless of whether these are of synthetic or natural origin) should not be assumed to produce exactly the same biological effects as synephrine alone.[2]

In physical appearance, synephrine is a colorless, crystalline solid and is water-soluble. Its molecular structure is based on a phenethylamine skeleton, and is related to those of many other drugs, and to the major neurotransmitters epinephrine and norepinephrine.