Pamoate

Pamoic acid
Names

Preferred IUPAC name 4,4'-Methylenebis(3-hydroxynaphthalene-2-carboxylic acid)
Other names 4,4'-Methylenebis(3-hydroxy-2-naphthoic acid) Embonic acid
Identifiers
CAS Number	130-85-8^Y
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	{{{Beilstein}}}
ChEBI	CHEBI:50186
ChemSpider	8228^Y
ECHA InfoCard	100.004.545
EC Number	204-998-0
IUPHAR/BPS	2920
MeSH	[www.nlm.nih.gov/cgi/show_data.php?acc={{{MeSH}}} {{{MeSH}}}]
PubChem CID	8546
RTECS number	QL2180000
UNII	7RRQ8QZ38N^Y
InChI InChI=1S/C23H16O6/c24-20-16(14-7-3-1-5-12(14)9-18(20)22(26)27)11-17-15-8-4-2-6-13(15)10-19(21(17)25)23(28)29/h1-10,24-25H,11H2,(H,26,27)(H,28,29)^Y Key: WLJNZVDCPSBLRP-UHFFFAOYSA-N^Y
SMILES OC(=O)C1=CC2=CC=CC=C2C(CC2=C(O)C(=CC3=CC=CC=C23)C(O)=O)=C1O C1=CC=C2C(=C1)C=C(C(=C2CC3=C(C(=CC4=CC=CC=C43)C(=O)O)O)O)C(=O)O
Properties
Chemical formula	C₂₃H₁₆O₆
Molar mass	388.38 g·mol⁻¹
Melting point	≥300 °C
log P	6.169
Acidity (pK_a)	2.675
Hazards
Main hazards	Causes skin irritation Causes serious eye irritation May cause respiratory irritation
EU classification (DSD) (outdated)	Xi
R-phrases (outdated)	R36/37/38
S-phrases (outdated)	S26 S36
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Causes serious eye irritation
May cause respiratory irritation

Pamoic acid, also called embonic acid, is a naphthoic acid derivative. Salts and esters of pamoic acid are known as pamoates or embonates. It can be prepared by the reaction of 2-hydroxy-3-naphthoic acid with formaldehyde.

In pharmacology, the salt form of pamoic acid (pamoate ion) can be used as a counter ion of a drug compound to increase the solubility of the drug in water. The presence of multiple oxygen atoms enables significant hydrogen bonding to occur. Hydrogen bonds facilitate the dissolution of compounds in water.

Pamoic acid has agonist activity for the orphan G protein-coupled receptor GPR35 by which it activates ERK and beta-arrestin2, and causes antinociceptive activity. Although (like other drug salts) it has been considered an inactive compound by the FDA, these recent data suggest that its permitted uses may need to be reexamined.

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