Rhubarb rhizome

Rheum officinale Baill. R. koreanum Nakai R. palmatum L. R. tanguticum Maxim R. undulatum L. Tai Huang (Rhubarb) (rhizome) Anthraquinones, chrysophanol, emodin, physcion, aloe-emodin, rhein, chrysophenol, rheum tannic acid, gallic acid, calechin, bianthraquinonyl, sennosides (R. undulatum also contains rhaponticin).1 33 236,510 This herb may be toxic. Potent laxative, antibacterial, anthelmintic, anticancer, stimulate the large intestine and increase the movement of luminal contents toward the anus, resulting in defecation. Antispasmodic, choleretic, hemostatic, diuretic, lower blood pressure, lower cholesterol level. 

For the first time, we have recently succeeded in obtaining preparations of stllbene synthase with reasonable specific activities in the range of mu/mg protein (15). At first, the enzyme was purified starting with acetone powders from rhubarb rhizomes. Till now the matter has not been brought to a very sophisticated level, but we provided evidence that p-coumaroyl-CoA and malonyl-CoA and not acetyl-CoA are the substrates, and we have data on the enzyme, on Mj- ( 70 000), Km for p-coumaroyl-CoA (120 iM), and the very pronounced substrate inhibition. 

We had to consider the selectivity or specificity of the stilbene synthase from rhubarb rhizomes In more detail as In this tissue the stilbene directly deriving from p-coumaric acid was hitherto unknown. Instead of this confound with a p-hydroxy group, another stilbene with an Isovanlllln structure (3-hydroxy-4-methoxy structure) is present there and already known for a long time rhapontlgenln (Fig. 4). 

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. 

Procyanidin C-l (condensed tannin) Rheum palmatum (rhubarb) (Polygonaceae) [rhizome] PKC... 

Undergroimd Stems.—A rhizome is a creeping underground stem, more or less scaly, sending off roots from its lower surface and stems from its upper. The rhizome grows horizontally, vertically or obliquely, bearing a terminal bud at its tip. Its upper surface is marked with the scars of the bases of aerial stems of previous years. Examples Triticum, Rhubarb, etc. 

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... 

I would like to discuss here also a very hypothetical concept of the enzyme s regulation. With rhubarb plants stilbenes are only synthesized in the rhizome. I wonder whether signals released in chloroplasts of leaf cells by light-mediated production of reduced thiol compounds can be passed on the cytoplasm or even to other cells, e. g. cells of the rhizome where a compound like thioredoxine could exert control of the activity of distinct enzyme, e. g. stilbene synthase. 

Rhubarb is believed to be a native of Asia minor. It is a perennial plant which forms large fleshy rhizomes and large leaves with long, thick petioles. It is one of the few vegetables in which the petiole is the part consumed. The leaf portion contains a toxic substance. Rhubarb s popularity in preserves, pies, and desserts causes many people to think of it as a fruit however, it is a vegetable. 

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. 

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