Tannins rhubarb

The pure substances would be too irritant, but their action is graded by their slow liberation and by the presence of colloid extractives. The most common of these substances are emodin and chrysophanic acid. Numerous isomers of these are possible (15 for emodin alone). The special character of the different drugs is probably due to differences in these isomers, in the stability of their glucosidal combination, and to the presence of other associated substances (tannin in rhubarb). 

Procyanidin C-l (condensed tannin) Rheum palmatum (rhubarb) (Polygonaceae) [rhizome] PKC... 

L., the common garden rhubarb. Rhubarb, like Ginseng and Ephedra, is one of the oldest and most widely used Chinese drugs. Chemically it contains a most complex mixture of anthracene glycosides, the most important of which are the dimeric Sennosides. Tannins are also found which can counteract the laxative effect and at low doses (0.05-0.5 g) it is their astringent effect that predominates. Higher doses of 1-2 g have a mild laxative effect. Extracts are also used in the treatment of mouth ulcers. 

A tannin isol. from commercial Chinese rhubarb Rheum spp.). Amorph. powder + IH2O. Mg +47 (c, 0.84 in MeOH). 

Nonaka G, Nishioka I, Nagasawa T, Oura H 1981 Tannins and related compounds Rhubarb. Chem Pharm Bull 29 2862-2870... 

Kashiwada Y, Nonaka G, Nishioka I 1986 Tannins and related compounds. XLV. Rhubarb (5). Isolation and characterization of flavan-3-ol and procyanidin glucosides. Chem Pharm Bull 34 3208-3222... 

Chinese rhubarbs contain two major classes of active constituents, anthraglycosides and tannins. 

The tannins in Chinese rhubarb are of both the catechin and gallic acid types, including t/-catechin, J-epicatechin gallate, gluco-gallin (galloylglucose), and others (list and... 

Indian rhubarb and garden rhubarb have been much less extensively investigated than Chinese rhubarb. Indian rhubarb is reported to contain tannins and anthraglycosides, many of which are probably the same as those of Chinese rhubarb. Garden rhubarb has been reported to contain chrysophanic acid (probably also its glucosides) but not the other anthraquinones or sennosides found in Chinese rhubarb it contains rhaponticin not present in Chinese or Indian rhubarb (martindale nanjing stahl). ... 

Kashiwada, Y., Nonaka, G. andNishioka, I. (1986) Tannins and related compounds. XLVlll. Rhubarb. Isolation and characterization of new dimeric and trimeric procyanidins. Chem. Pharm. Bull. (Tokyo), 34,4083 91. 

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