Action ► Purgative, astringent, aperient. Used for constipation and atonic dyspepsia. Not advised for patients suffering from gout, rheumatism, epilepsy. (When given internally, the root imparts a deep tinge to the urine.)
The root gave emodin, emodin-3-monomethyl ether, chrysophanol, aloe-emodin, rhein. These occur free and as quinone, anthrone or dianthrone glycosides. The astringent principle consists of gallic acid together with small amounts of tannin. The drug also contain cinnamic and rhe-inolic acids, volatile oil, starch and
Rheum nobile Hook. f. &Th.
calcium oxalate. Two major glyco-sidic active principles, sennoside A and B, are present along with free an-thraquinones.
At low doses, the tannin exerts astringent effect and relieves diarrhoea; at higher doses anthraquinones stimulate laxative effect and relieve constipation. (Natural Medicines Comprehensive Database, 2007.)
There are three main types of rhubarbs—Chinese, Indian or Himalayan, and Rhapontic.
The Chinese rhubarb consists of the rhizomes and roots of Rheum palma-tum and R. officinale.
The Indian rhubarb consists of dried rhizomes of R. emodi and R. web-bianum; rhizomes and roots of R. moorcroftianum and R. spiciforme are also reported to be mixed with the drug. R. rhaponticum is the Rhapontic rhubarb.
Rheum moorcroftianum Royle (the Himalayas at altitudes of 3,0005,200 m., chiefly in Garhwal and Ku-maon) possesses properties similar to those of R. emodi and the roots are mixed with the latter.
Rheum spiciforme Royle (drier ranges of Kumaon and Sikkim at altitudes of 2,700-4,800 m.) also possesses purgative properties. The rhizomes and roots are mixed up with Himalayan rhubarb.
Rheum webbianum Royle (the western and central Himalayas at altitudes of 3,000-5,000 m.) is the source of Himalayan rhubarb.
Rheum palmatum is esteemed as the best type of (Chinese) rhubarb. Two new stilbene glycosides, 4'-O-methylpiceid and rhapontin, isolat ed from the roots, exhibited moderate alpha-glucosidase inhibitory activity. Anthraquinone glucoside, pul-matin, isolated from the roots, along with its congeners, chrysophanein and physcionin, showed cytotoxic activity against several types of carcinoma cells. Polysaccharides, isolated from the roots and rhizomes, contained lyx-ose, glucose, galactose, xylose, rham-nose, mannose and ribose.
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