High-Performance Thin-Layer Chromatography for the Analysis of MedicinalPlants presents the theoretical and technical information
needed to performreliable and reproducible high-performance thin-layer chromatography (HPTLC) toestablish the identity, purity, quality, and stability of raw materials,extracts, and finished botanical products. It is a simple means ofquantification by measurement of the optical density of the separated spotsdirectly on the plate. All these aspects are enable substantial improvement ofin-situ quantitative densitometric analysisThe text provides a complete overview of the technique and common applicationsof HPTLC in herbal analysis. Rhizoma Rheiconsists of the underground parts (rhizome and root) of Rheum officinaleBaill., The fruit is an ovoid-oblong or orbicular achene bearing 3 broadmembranous wings and the remains of the perianth at the base.The appearance ofthe rhizomes and roots varies according to the plant's geographical origin. Thetransverse section of the rhizome shows wavy medullary rays, 2-4 cells inwidth; the xylem consists of a matrix of wood parenchyma and resembles thephloem and cortex regions in that the cells possess either starch, tannin, orlarge cluster crystals of calcium oxalate. The bundles differ from the ordinaryopen collateral bundle in showing phloem inside and xylem outside the cambium. InR. officinale the compound bundles ("stellate spots") are scatteredthrough the pith, whereas in R. palmatum they are mostly arranged in a ring,the remainder being scattered on either side of the ring.Powdered Rhizoma Rhei is dusky yellowish orange to moderate yellowish brown,and coloured red in the presence of alkali. and Oinghai provinces), theDemocratic People's Republic of Korea and the Republic of Korea. The maximumacceptable limits of other microorganisms are as follows. Normally, themaximum residue limit of aldrin and dieldrin in Rhizoma Rhei is not more than0.05 mg/kg. Recommended lead an dcadmium levels are no more than 10 and 0.3mg/kg,respectively, in the final dosage form of the plant material.The level of the oxidized forms is maximal in thesummer and almost nil in the winter. Until the 1950s, chrysophanol and otheranthraquinones were considered to be the constituents producing the purgativeaction of rhubarb. As shown for senna, the mechanism of action is twofold: (1)stimulation of colonic motility, which augments propulsion and acceleratescolonic transit (which in turn reduces fluid absorption from the faecal mass);and (2) an increase in the paracellular permeability across the colonic mucosaprobably owing to an inhibition of Na + /K+ .-exchanging ATPase or to aninhibition of chloride channels which results in an increase in the water contentin the large intestine. The active constituents of Rhizoma Rhei are theanthraquinone glycosides, sennosides A-F and
rheinosides A-D. The rheinosidesare similar to aloin A and B, the main cathartic principles of aloe. Thecathartic action of both the sennosides and rheinosides is limited to the largeintestine, where they directly increase motor activity in the intestinal tract.The mechanism of action is similar to that of other anthraquinone stimulantlaxatives. Both the sennosides and rheinosides are hydrolysed by intestinal bacteriaand then reduced to the active anthrone metabolite, which acts as a stimulantand irritant to the gastrointestinal tract. The major symptoms of overdose aregriping and severe diarrhoea with consequent losses of fluid and
electrolytes. Electrolytes,particularly potassium should be monitored, especially in children and theelderly.The use of stimulant laxatives for more than 2 weeks requires medicalsupervision.Chronic use may lead to pseudomelanosis coli(harmless) and to an aggravation of constipation with dependence and possibleneed for increased dosagesChronicabuse with diarrhoea and consequent fluid and electrolyte losses (mainlyhypokalaemia) may cause albuminuria and haematuria, and it may result incardiac and nromilscufar dysfunction. the latter particularly in case ofconcomitant use of cardiac glycosides (digoxin), diuretics, corticosteroids. Theteratogenic effects of Rhizoma Rhei have not been evaluated.Use of Rhizoma Rhei for children under 10 years of age is contraindicated.