Emodin

Emodin (6-methyl-1,3,8-trihydroxyanthraquinone) is an organic compound. Classified as an anthraquinone,it can be isolated from rhubarb, buckthorn, and Japanese knotweed (Reynoutria japonica syn. Polygonum cuspidatum). Emodin is particularly abundant in the roots of the Chinese rhubarb (Rheum palmatum), knotweed and knotgrass (Polygonum cuspidatum and Polygonum multiflorum) as well as Hawaii ‘au‘auko‘i cassia seeds or coffee weed (Semen cassia). It is specifically isolated from Rheum palmatum L. It is also produced by many species of fungi, including members of the genera Aspergillus, Pyrenochaeta, and Pestalotiopsis, inter alia. The common name is derived from Rheum emodi, a taxonomic synonym of Rheum australe, (Himalayan rhubarb) and synonyms include emodol, frangula emodin, rheum emodin, 3-methyl-1,6,8-trihydroxyanthraquinone, Schüttgelb (Schuttgelb), and Persian Berry Lake.

Pharmacology
Emodin is an active component of several plants used in traditional Chinese medicine (TCM) such as Rheum palmatum, Polygonum cuspidatum, and Polygonum multiflorum. It has various actions including laxative, antibacterial and antiinflammatory effects, and has also been identified as having potential antiviral activity against coronaviruses such as SARS-CoV-2,  being one of the major active components of the antiviral TCM formulation Lianhua Qingwen.

Emodin has been shown to inhibit the ion channel of protein 3a, which could play a role in the release of the virus from infected cells.

List of species
The following plant species are known to produce emodin: Emodin also occurs in variable amounts in members of the crustose lichen genus Catenarina.
 * Acalypha australis
 * Cassia occidentalis
 * Cassia siamea
 * Frangula alnus
 * Glossostemon bruguieri
 * Kalimeris indica
 * Polygonum hypoleucum
 * Reynoutria japonica (syn. Fallopia japonica) (syn. Polygonum cuspidatum )
 * Rhamnus alnifolia, the alderleaf buckthorn
 * Rhamnus cathartica, the common buckthorn
 * Rheum palmatum
 * Rumex nepalensis
 * Senna obtusifolia (syn. Cassia obtusifolia )
 * Thielavia subthermophila
 * Ventilago madraspatana

Compendial status

 * British Pharmacopoeia


 * List of compounds with carbon number 15