Rhein (molecule) explained

Rhein, also known as cassic acid, is a substance in the anthraquinone group obtained from rhubarb.^[1] Like all such substances, rhein is a cathartic, which is commonly found as a glycoside such as rhein-8-glucoside or glucorhein. Rhein was first isolated in 1895.^[2] It is found in rhubarb species like Rheum undulatum^[3] and Rheum palmatum^[4] as well as in Cassia reticulata.^[5]

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.^[6] Synergy or partial synergy has been demonstrated between rhein and the antibiotics oxacillin and ampicillin.^[7]

Rhein has been shown to inhibit the fat mass and obesity-associated protein, an enzyme responsible for removing the methylation from N⁶-methyladenosine in nucleic acids.^{[8] [9]}

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.^[10] 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.^[11]

See also

• Diacerein

Notes and References

1. http://pharmaxchange.info/press/2012/12/pharmacognosy-of-rhubarb/ Pharmacognosy of Rhubarb | Chemical Constituents
2. Hesse O . 1895 . The Chemistry of rhubarb (EN). . Pharmaceutical Journal and Transactions . 1 . 325.
3. Lee JH, Kim JM, Kim CS . Pharmacokinetic analysis of rhein in Rheum undulatum L. . J Ethnopharmacol . 2003 . 84 . 1. 5–9 . 12499069 . 10.1016/S0378-8741(02)00222-2.
4. Hoerhammer L, Wagner H, Koehler I. Neue Untersuchungen über die Inhaltsstoffe von Rheum palmatum L. 1. Mitteilung: Zur Analytik des Rheins . New investigations on the components of Rheum palmatum L. Part 1: On the analysis of rhein . Archiv der Pharmazie . 1959. 292. 64 . 591–601 . 14402302. 10.1002/ardp.19592921105. 94169376 . de .
5. Anchel M. Identification of the antibiotic substance from Cassia reticulata as 4,5-Dihydroxyanthraquinone-2-carboxylic acid . J Biol Chem . 1949 . 177 . 169–177. 1 . 10.1016/S0021-9258(18)57072-1 . 18123056 . free .
6. Yu L, Xiang H, Fan J, etal . Global transcriptional response of Staphylococcus aureus to rhein, a natural plant product . J Biotechnol . 2008 . 135. 3 . 304–308 . 18514345 . 10.1016/j.jbiotec.2008.04.010.
7. Joung DK, Joung H, Yang DW, etal . Synergistic effect of rhein in combination with ampicillin or oxacillin against methicillin-resistant Staphylococcus aureus . Exp Ther Med . 2012. 3. 4. 608–612 . 22969937 . 10.3892/etm.2012.459 . 3438619.
8. Yu. Jun. Chen. Mengxian. Huang. Haijiao. Zhu. Junda. Song. Huixue. Zhu. Jian. Park. Jaewon. Ji. Sheng-Jian. 2017-11-23. Dynamic m⁶A modification regulates local translation of mRNA in axons. Nucleic Acids Research. en. 46. 3. 1412–1423. 10.1093/nar/gkx1182. 0305-1048. 5815124. 29186567.
9. Jia. Guifang. Fu. Ye. Zhao. Xu. Dai. Qing. Zheng. Guanqun. Yang. Ying. Yi. Chengqi. Lindahl. Tomas. Pan. Tao. 2011-10-16. N⁶-Methyladenosine in nuclear RNA is a major substrate of the obesity-associated FTO. Nature Chemical Biology. En. 7. 12. 885–887. 10.1038/nchembio.687. 1552-4450. 3218240. 22002720.
10. Zhu W, Wang XM, Zhang L, Li XY, Wang BX . Pharmacokinetic of rhein in healthy male volunteers following oral and retention enema administration of rhubarb extract: a single dose study . Am J Chin Med . 2005. 33. 6. 839–850 . 16355440 . 10.1142/S0192415X05003508.
11. La Villa G, Marra F, Laffi G, etal . Effects of rhein on renal arachidonic acid metabolism and renal function in patients with congestive heart failure . Eur J Clin Pharmacol . 1989. 37. 1. 1–5 . 2512175 . 10.1007/bf00609415. 6338421 .