संस्कृत नाम- अम्लवॆतसः
Botanical name - Rheum emodi
Description - A tall herb with very stout stems and roots. Lower leaves very large, about 60-cm diameter, round, on very stout, 30-45 long petioles. Flowers minute, dark purple, in a very large bunch. Fruit 1.3 cm long, purple
Chemical_Constituents- It contains anthraquinone derivatives, glucogallin, tannin and catechin. The anthraquinone derivatives are rhein emodin, aloe-emodin, emodin monomethyl ether and chrysophanol.
Uses - The dried rhizomes of Rheum emodi constitute the drug. The rhizomes of Rheum webbianum Royle (Archu) are also accepted. The rhizomes should be collected from 6-7 year old plants just before the flowering season; they should not be decorticated. Rhubarb is used as purgative. The drug also has tannins and therefore after purgation it creates an astringent effect, which causes constipation. Rhubarb is not suitable cases of chronic constipation, but only in mild ones. Due to astringent action Rhubarb is also given in certain types of diarrhoea, e.g. those caused by presence of any irritate substances in intestines.