RHUBARB (Rheum palmatum var. tanguticum Maxim.) — medicinal plant this. buckwheat (Polygonaceae), possessing laxative action.
A perennial herbaceous plant up to 2,5 m high with a many-domed rhizome and departing from it large, fleshy, on a section yellow roots. Radical leaves very large, with scapes up to 30 cm long; plates of leaves to 75 cm in the diameter. In a form leaves shirokoyaytsevidny, 5 — 7-bladed, from below hoary; the blades of leaves pointed, neravnokrupnonadrezanny. Stem leaves smaller, with bells at the basis. Flowers whitish-pink or red, collected in panicled inflorescences. Fruits — trihedral, brownish-red, broad-winged nutlets. Grows in Sowing. - Zap. China and Tibet.
In the USSR R. is cultivated commercially. As medicinal raw materials use roots (radix Rhei) with a small amount of rhizomes, to-rye collect on the 4th year of life of a plant. Roots and R.'s rhizomes contain two basic groups pharmacological of active agents — antraglikozida (gluco-reum-oemodin, hrizofanein, rheochrysin, glyuko-rein and gluco-aloe-oemodin) and tanning agents. Along with glycosides are present at raw materials as well their aglikona (reum-oemodin, hrizofa-nol, fistsion, Rhine and an aloe oemodin). Antraglikozida R. are capable to condensation with formation of dimeric connections. The general maintenance of all derivatives of anthracene in roots shall be not less than 3,4%. Content of tanning agents (gallotanin) — to 12%.
On pharmakol. to properties drugs of a root P. belong to to purgatives (see), acting preferential on a large intestine. The laxative effect of these drugs is caused by irritant action of the antraglikozid which are contained in them on interoretseptor of intestines. At the same time there is strengthening of a tone and vermicular movement of hl. obr. a large intestine since antraglikozida collect in enough only in this department of intestines. It is possible also that receptors of a large intestine are more sensitive to antraglikozida, than receptors of a small bowel.
At administration of drugs of R. in small doses the peristaltics of intestines is weakened owing to the knitting action of gallotanin on a mucous membrane.
In medical practice the following drugs of a root P are used.
Tablets of a rhubarb (Tabulettae radicis Rhei) — yellow-brown color, contain 0,3 or 0,5 g of a melkoizmelchenny root P. As laxative is appointed inside the adult on 0,5 — 2 g to reception; to children of 2 years — 0,1 g, 3 — 4 years — 0,15 g, 5 — 6 years — 0,2 g, 7 — 9 years — 0,25 — 0,5 g, 10 — 14 years — 0,5 — 1 g on reception.
Extract of a rhubarb of dry (Extractum Rhei siccum) — powder of yellowish-brown color, bitterish taste, with a peculiar smell. Contains not less than 3% of derivatives of anthracene. Appoint as laxative in from 0,1 to 1 — 2 g to reception (depending on age).
All drugs of a root P. store in the cool, protected from light place.
See also Medicinal plants .
Bibliography: Medicinal plants, under the editorship of A. I. Bankovsky, page 504, M., 1969; Muravyeva D. A. A pharmacognosy (with fundamentals of biochemistry of medicinal substances), page 505, M., 1981.
D. A. Muravyeva.