Rhubarb species

Rhubarb consists of the dried underground parts of R. paimatum, R. officinale, or of both species. Stem parts, roots, and most of the bark are removed from the rhizomes. 

It is a white solid used in removal of certain kinds of stains, in removing calcium ions from solutions, and in tanning leather. It occurs naturally and is toxic. The potassium and calcium salts of oxalic acid are found naturally in cabbage, spinach, and rhubarb leaves, and are also found in the bark of some species of eucalyptus trees. The metabolism of sugar by many species of mold results in the production of oxalic acid. Ingestion of large amounts can cause kidney damage, convulsions, and death. 

Petasites species have hepatotoxic potential, owing to the presence of pyrrolizidine alkaloids, which are covered in a separate monograph. Extracts of Petasites hybridus (blat-terdock, bog rhubarb, butterbur, butterdock) contain ht-tle in the way of these alkaloids (31). Butterbur has been used to treat allergic rhinitis and asthma and in the prevention of migraine. 

Rheum palmatum (rhubarb) Aconitum napellus (monkshood) Cimicifuga racemosa (black cohosh) Delphinium species (delphinium) Hydrastis canadensis (golden seal) Pulsatilla species (pasque flower) Ranunculus damascenus (buttercup)... 

The axillary group represent stipules which stand in the axil of the leaf with the stem. Such may be free axillary structures, arising as distinct processes, or connate, when the two stipules unite at their margins and sheath the stem, as in many species of the Polygonacea such as Buckwheat, Rhubarb, Yellow Dock, Knot Weeds, etc. The sheath formed is called an ochrea. 

Emodin (l,6,8-trihydroxy-3-methylanthraquinone), the active principle of Polygonum cuspidatum (Polygonaceae), was reported to be an inhibitor of the p56 -PTK activity from bovine thymus, with an IC50 of 18.5 pM. When the hydroxyl functions at C-6 or C-8 were blocked by methylation or glycosylation, respectively, the effect disappeared. The inhibition was competitive with respect to ATP and non competitive with respect to the substrate [64]. In a bioassay-guided separation of the anthraquinones found in rhizomes of another Polygonaceae species, rhubarb Rheum... 

RHUBARB ROOT, Rhei radix Medicinal Rhubarb consists of the peeled and dried root of Rheum species, chiefly Rheum officinale Baill. and R. palmatum L., family Polygonaceae, but not of Rheum rhaponticum... 

AGARWAL s K, SINGH s s, LAKSHMi V, VERMA s and KUMAR s (2001), Chemistry and pharmacology of rhubarb Rheum species) - A review , J. Sci IndRes, 60, 1-9. 

C16H12O5, Mr 284.27, orange needles, mp. 209-210 °C, uv ,a, 431 nm (C2H5OH). An octaketide that occurs in senna leaves (Cassia senna, Fabaceae), rhubarb roots, in chrysarobinum (see chrysarobin), lichens (Parmelia species), and fungi (Aspergillus and Penicillium species), as well as in glycosidically bound form in Cassia species. It has a weak spasmolytic activity. 

S. A-G occur in the leaves and fruits of Cassia species (C. senna, C. angustifolia, Fabaceae) and in rhubarb roots, sometimes as oxalyl derivatives (senno-sides E, F). S. are mostly formed from the corresponding anthrone glycosides when the senna leaves are dried. Drugs containing S. are used in therapy for acute constipation (see table, p. 581). 

Constituent, of variod s species of rhubarb Rheum), of cassia, goa, etc. Golden-yellow cryst. M.p. 196". Sol. MejCO, AcOH, CHClj, hot EtOH, hot C,PL. Spar. sol. HgO, ligroin, Et,0. Sublimes, (jonc. H Og —> red col. Sol. caustic alkalis, hot alk. c bonates Zn dust dist.—>. 2-methylanthiacehe. 

Secondary compounds with similar structures, for example, polygonaquinone (5) (Figs. 6.1 and 6.2), are encountered in species of Fagopyrum (buckwheat). Polygonum (smart-weed), Rumex (dock), and Rheum (rhubarb) in the Poly-gonaceae (Mathis, 1966). 

Anthraquinone glycosides have long been used medicinally as cathartics and laxatives. Plant-derived drugs of this type include aloes Aloe species), cascara sagrada (Rhamnus purshiams), frangula (Rhamnus frangula), rhubarb (Rheum officinale), rumex or yellow dock (Rumex crispus) and senna (Cassia spp.). Many of the commercial preparations (patent medicines) based on these plants are readily available. 

A scholastic exception was typically made for the elements, which were said to be capable of return from a mixture in specie but not in numero. What this amounted to was that a new element, say water, could be formed from water that had become air. The new water would be specifically the same as the original water but numerically different. Sennert alludes to the distinction between acquiring something in numero and in specie at De chymicorum, 1619, p. 686, where he is discussing extraction of alcohol from wine and the active, purging ingredient from rhubarb. 

Stilbenes originate from the same biosynthetic precursors as flavonoids, but have a different structure, since the polyketide portion undergoes a different type of cyclization including loss of one carbon by decarboxylation. Stilbenes occur in several umelated plants such as peanut (Arachis hypogaea), grapevine (Vitis vinifera), rhubarb (Rheum), false hellebores (Veratrum) and pine (Pinus) species. These compounds have antifungal properties. They are induced upon stress, injury, and fungal infection and can therefore be classified as phytoalexins. 

Relatively rare compounds are lavan-3-ol glycosides. For example, (+)-catechin-7-0-P-D-glucoside has been isolated from several plant species, such as barley, buckwheat, vigna and rhubarb. Usually, 7-O-P-D-glucosides coexists in plants with other isomeric glucosides, such as 5-0-, A -O- and 3 -0-P-n-glucosides. 

The anthraquinone compound Rhein, 1,8-dihydroxy an-thriquinone-3-carboxylic acid, is found in various Cassia and Rheum species MerckIndex, 1996). It is also known as rhubarb yellow . 

Source Chinese rhubarb Rheum officinale Bail ., R. palmatum L., R. tanguticum Maxim, ex Reg., and other Rheum species or hybrids grown in China Indian rhubarb... 

Large and sturdy, perennial herbs with large leaves home on thick petioles stem up to 2-3 m high native to Asia (e.g., China, India, and southern Siberia) widely cultivated. Parts used are the dried rhizome and roots deprived of periderm (corky layer). Only plants 3 y or older are used. Chinese rhubarb, especially those from R. officinale and R. palmatum, are considered to be of the best quality. Those species with palmate rather than undulate leaves are generally considered the official drug source species or substitutes in China. 

---