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

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxo ...

group obtained from

rhubarb Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The whole plant – a herbaceous perennial growing from short, thick rhizo ...

.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 cathart ...

. Rhein 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

species like ''

Rheum undulatum ''Rheum rhabarbarum'' is a species of flowering plant in the family Polygonaceae, native to a region stretching from southern Siberia to north and central China. It has been harvested from the wild for centuries for its root, which was harvested ...

'' and ''

Rheum palmatum ''Rheum palmatum'' is a species of flowering plant in the knotweed family Polygonaceae. It is commonly called Chinese rhubarb, ornamental rhubarb, Turkey rhubarb or East Indian rhubarb. ''Rheum palmatum'' is a herbaceous perennial related to th ...

'' as well as in ''

Cassia reticulata ''Senna reticulata'', the ''mangerioba grande'' or ''maria mole'' in Portuguese, is a pioneer tree species found on highly fertile floodplains in South America. It has some medicinal uses, but is regarded by farmers as a noxious weed, named ''mat ...

''. 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 positive ...

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

oxacillin Oxacillin (trade name Bactocill) is a narrow-spectrum beta-lactam antibiotic of the penicillin class developed by Beecham. It was patented in 1960 and approved for medical use in 1962. Medical uses Oxacillin is a penicillinase-resistant β ...

and

ampicillin Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, and endocarditis. It may also be used to prevent group B strepto ...

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

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

from N⁶-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 determining the fate of substances administered ...

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