Synephrine

This article will focus, insofar as possible, on synephrine itself, rather than on the drug mixtures containing it.
Synephrine
Names
Preferred IUPAC name
4-[1-Hydroxy-2-(methylamino)ethyl]phenol
Other names
p-Synephrine; Oxedrine; 4,β-Dihydroxy-N-methylphenethylamine
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.092 Edit this at Wikidata
KEGG
UNII
  • InChI=1S/C9H13NO2/c1-10-6-9(12)7-2-4-8(11)5-3-7/h2-5,9-12H,6H2,1H3 checkY
    Key: YRCWQPVGYLYSOX-UHFFFAOYSA-N checkY
  • InChI=1/C9H13NO2/c1-10-6-9(12)7-2-4-8(11)5-3-7/h2-5,9-12H,6H2,1H3
    Key: YRCWQPVGYLYSOX-UHFFFAOYAW
  • CNCC(O)c1ccc(O)cc1
Properties
C9H13NO2
Molar mass 167.21 g/mol
Appearance colorless solid
Melting point 162 to 164 °C (324 to 327 °F; 435 to 437 K) (R-(−)-enantiomer); 184 to 185 °C (racemate)
soluble
Pharmacology
C01CA08 (WHO) S01GA06 (WHO), QS01FB90 (WHO)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Synephrine, or, more specifically, p-synephrine, is an alkaloid, occurring naturally in some plants and animals, and also in approved drugs products as 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 epinephrine and 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 (枳实), 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 over the counter drug. As a pharmaceutical, m-synephrine (phenylephrine) 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]

There is a difference between studies concerning synephrine as a single chemical entity (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.

  1. ^ SA, HCI Solutions. "Neo-Synephrine HCl - compendium.ch". compendium.ch. Archived from the original on 2020-07-25. Retrieved 2016-03-06.
  2. ^ Wagner H., Ulrich-Merzenich G. (2009). "Synergy research: approaching a new generation of phytopharmaceuticals". Phytomedicine. 16 (2–3): 97–110. doi:10.1016/j.phymed.2008.12.018. PMID 19211237. S2CID 25766699.


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