Description of medicine: Rhubarb roots (Radices Rhei)
Roots of Rhubarb (Radices Rhei).
Collected in autumn or early spring at least 3 years old, peeled, cut into pieces, dried roots and rhizomes of the cultivated in our country Tangut rhubarb (Rheum palmatum L., var tanguticum Maxim) herbaceous perennial plant, fam. buckwheat (Rolugoneceae).
Rhubarb roots and rhizomes contain anthraglycosides, tanoglycosides, chrysophanic acid, tarry, coloring and other substances.
Antraglycosides are ether-like compounds which, after cleavage of sugar, form emodin and other anthracene derivatives. The total content of anthracene derivatives in the roots of rhubarb is at least 2% (in terms of istizine).
The main active ingredients are emodin (trioxymethylanthraquinone) and chrysophane acid (dioximethylanthraquinone). They irritate the intestinal interoreceptors and cause increased peristalsis, while exerting a predominant effect on the large intestine and causing its more rapid emptying.
The laxative effect after taking rhubarb preparations occurs after 810 hours. The slow effect and predominant effect on the large intestine is usually explained by the fact that the decomposition of anthraglycosides in the intestine occurs gradually and the active substances accumulate in the amount necessary for a laxative effect, only when they reach the large intestine . Colon mucosal receptors are most sensitive and respond to concentrations of emodin that the small intestine receptors do not respond to. In addition, after absorption in the small intestine, anthraglycosides are converted in the body into emodin, which is released in the large intestine and enhances its peristalsis.
Rhubarb preparations are prescribed in powders, pills, decoctions, alone and in combination with other substances as laxatives, mainly for chronic (habitual) constipation. They are usually recommended at night, are well tolerated and do not interfere with the absorption processes and normal activity of the small intestine. The resinous substances contained in the plant may have some irritating effect on the intestines.
Sometimes rhubarb preparations are taken in small doses (0.05 - 0.2 g) as astringents that reduce intestinal motility. Their astringent effect is due to the presence of tanoglycosides, which, when bound to proteins, precipitate them, forming a precipitate that protects the receptors of the mucous membrane.
When taking rhubarb preparations, the urine, sweat and milk of nursing mothers turn yellow (the presence of chrysophanic acid), which turns red when alkali is added (the formation of hydroxymethylantraquinones).
The following rhubarb preparations are used.
Rhubarb powder (Pulvis radicis Rhei). The powder is yellow-orange or red. Crunches on the teeth due to the content of crystals of calcium oxalate.