Rhein, also known as cassic acid, is a substance in the

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic hydrocarbon, aromatic organic compound with formula . Several isomers exist but these terms usually refer to 9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein th ...

group obtained from rhubarb.Pharmacognosy of Rhubarb , Chemical Constituents
/ref> Like all such substances, rhein is a

cathartic In medicine, a cathartic is a substance that ''accelerates'' defecation. This is similar to a laxative, which is a substance that ''eases'' defecation, usually by softening feces. It is possible for a substance to be both a laxative and a cathar ...

, which is commonly found as a

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

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 ''Rheum palmatum'' is a species of flowering plant in the knotweed family (botany), family Polygonaceae. It is commonly called Chinese rhubarb, ornamental rhubarb, Turkey rhubarb or East Indian rhubarb. ''Rheum palmatum'' is a herbaceous peren ...

'' 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 ''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often posi ...

'' in 2008. Synergy or partial synergy has been demonstrated between rhein and the antibiotics oxacillin and

ampicillin Ampicillin is an antibiotic belonging to the aminopenicillin class of the penicillin family. The drug is used to prevent and treat several bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, s ...

. Rhein has been shown to inhibit the fat mass and obesity-associated protein, an enzyme responsible for removing the

methylation Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...

from ''N''⁶-methyladenosine in nucleic acids. The

pharmacokinetics Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to describing how the body affects a specific su ...

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.

References

{{Retinoid receptor modulators CYP2D6 inhibitors Dihydroxyanthraquinones

See also

References