Rhein (molecule)

Rhein

Names
IUPAC name 4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid
Other names Rhubarb Yellow Monorhein Cassic acid Rheic acid Chrysazin-3-carboxylic acid
Identifiers
CAS Number	478-43-3 Y=
3D model (Jmol)	Interactive image
ChemSpider	9762 N
ECHA InfoCard	100.006.839
MeSH	Rhein
PubChem CID	10168
InChI InChI=1S/C15H8O6/c16-9-3-1-2-7-11(9)14(19)12-8(13(7)18)4-6(15(20)21)5-10(12)17/h1-5,16-17H,(H,20,21) N Key: FCDLCPWAQCPTKC-UHFFFAOYSA-N N InChI=1/C15H8O6/c16-9-3-1-2-7-11(9)14(19)12-8(13(7)18)4-6(15(20)21)5-10(12)17/h1-5,16-17H,(H,20,21) Key: FCDLCPWAQCPTKC-UHFFFAOYAT
SMILES C1=CC2=C(C(=C1)O)C(=O)C3=C(C=C(C=C3C2=O)C(=O)O)O
Properties
Chemical formula	C15H8O6
Molar mass	284.22 g/mol
Appearance	Orange crystals
Density	1.687 g/cm3
Melting point	350 to 352 °C (662 to 666 °F; 623 to 625 K)
Boiling point	597.8 °C (1,108.0 °F; 870.9 K) at 760 mmHg
Solubility in water	Insoluble in water
Hazards
Main hazards	Irritant
EU classification (DSD)	Xi
R-phrases	R36/R37/R38
S-phrases	S26-37/S39
Flash point	329.4 °C (624.9 °F; 602.5 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Rhein, also known as cassic acid, is a substance in the anthraquinone group obtained from rhubarb. Like all such substances, rhein is a cathartic. Rhein is commonly found as a glycoside such as rhein-8-glucoside or glucorhein. Rhein was first isolated in 1895. It is found in rhubarb species like Rheum undulatum and Rheum palmatum as well as in Cassia reticulata.

Originally the rhubarb plant which contains rhein was used as a laxative. It was believed that rhein along with other anthraquinone glycosides imparted this activity.

Rhein has been reevaluated as an antibacterial agent against Staphylococcus aureus in 2008. Synergy or partial synergy has been demonstrated between rhein and the antibiotics oxacillin and ampicillin.

The pharmacokinetics of rhein have not been intensively studied in humans, but at least one study in healthy male volunteers found that rhein was better absorbed from oral administration of rhubarb than from a retention enema. Rhein (at an oral dose of 50 mg twice per day) was shown to be safe when administered for five days to elderly patients with chronic congestive heart failure.