Saponins Pharmacognosy I Mosul University/ college of Pharmacy L.A. Dilbreen Barzanji

Introduction Plant materials containing saponins have long been used in many parts of the world for their detergent properties. For ex. In Europe the root of Saponoria officinalis and in South America the bark of Quillaja saponoria. Such plants contain high percentage of glycosides known as saponins (Latin sapo, soap) which are characterized by their property of producing a frothing aqueous solution. They also have hemolytic properties, and when injected into the blood stream, are highly toxic. The fact that a plant contains hemolytic substances is not proof that it contains saponins.

When taken by mouth, saponins are comparatively harmless. Saponins have a high molecular weight and a high polarity and their isolation in a state of purity presents some difficulties. As glycosides they are hydrolysed by acids to give an aglycone (sapogenin) and variuos sugars and related uronic acids. According to structure of aglycone or sapogenin, two types of saponins are recognized: Steroidal (commonly tetracyclic triterpenoids) Pentacyclic triterpenoids saponins

Steroidal saponins The steroidal saponins are less widely distributed in nature than the pentacyclic terpenoid type. Steroidal saponins are of great pharmaceutical importance because of their relationship to compounds such as the sex hormones, diuretic steroids, vitamin D and the cardiac glycosides. As with other cardiac glycosides, the steriochemistry of the molecule is of some importance. Natural sapogenins differ only in their configuration at carbon atoms 3, 5 and 25.

Natural steroids for the production of pharmaceuticals Although total synthesis of some medicinal steroids is employed commercially , there is also a great demand for natural products which will serve as starting materials for their partial synthesis. Hecogenin with C-ring substitution provides a practical starting material for the synthesis of cortecosteroids, whereas diosgenin is suitable for the manufacture of oral contraceptives and the sex hormones. Diosgenin can also be used for cortecosteroid synthesis by the employment of a microbial fermentation (at a suitable stage in syntheisis) to introduce oxygen into the 11 α-position of pregnene nucleus.

Dioscorea species Tubers of many of the Dioscoreas (yams) have long been used for food, as they are rich in starch. In addition to starch some species contain steroidal saponins, others alkaloids. Form a suitable source the sapogenins are isolated by acid hydrolysis of saponin. Previous fermentation of the material for some 4-10 days often gives a better yield. The water-insoluble sapogenin is then extracted with a suitable organic solvent.

Both wild and cultivated plants are used. According to the species, the tubers reach maturity in 3-5 years and on average, yeild 1-8% total sapogenin. Until 1970 diosgenin isolated from the Maxican yam was the sole source of contraceptive manufacture. China is now exporting large quantities of diosgenin; it is of high quality and reasonably priced. Three of many Dioscorea species found in China and used commercially.

Ginseng For some 2000 years the roots of Panax ginseng have held an honored place in Chinese medicine. Today it is a product of world wide usage. Production is principally confined to China, Korea and Siberia, although it is cultivated commercially in other countries. The most expensive ginseng is that derived from Korean root.

White ginseng is obtained by sun drying of the root after removal of the outer layers. Red ginseng is obtained by first steaming the root, followed by artificial drying then sun drying. Rootlets are numerous on the lower surface of white ginseng but normally absent from red ginseng. The roots are graded and packed. The scraping of the roots before drying would appear to be disadvantageous because histochemical tests and GLC analysis is show the active saponins to be located outside the root cambium.

Constituents of Ginseng roots Panax ginseng roots have been thoroughly studied by modern methods of analysis and, of many compounds isolated , the medicinal activity appears to reside largely in a number of dammarane-type saponins termed ginsenosides by Japanese researchers and panaxosides by Russian researchers . These two series of compounds all now generally termed ginsenosides, are glycosides respectively derived from the diol 20(S)-protopanaxadiol and the triol 20(S)-protopanaxatriol. Acid hydrolysis of these saponins involves ring closure of the aglycone giving either panaxadiol or panaxatriol.

Glucose is the principal sugar involved with some input of arabinose and rhamnose. Some 30 ginsenosides have been named. The BP/EP specifies a minimum of 0.40% for the sum of ginsenosides Rg1 and Rb1.

Two other groups of compounds present in the root which have known therapeutic activity are high molecular weight polysaccharides (glycans) and acetylenic compounds. The glycans of Panax ginseng have been named panaxan (A-U).those glycans tested have hypoglycemic, antiulcer, and immunological properties. A considerable number of mainly C17, but also C14, polyacetylenic alcohols have been isolated from the roots called panaxynol and panaxydol. These compounds have shown antitumer properties.

Uses In Asia, it used in the treatment of anaemia, diabetes, gastritis, sexual impotence and the many conditions arising from the onset of old age. In the west, it has in recent years become an extremely popular remedy particularly for the improvement of stamina, concentration, resistance to stress and to disease; in this sense of action of the drug is described as ‘adaptogenic’. Many ‘ginsneg’ products are available as OTC products either for oral administration or as cosmetic preparation.

Saponins (cont’d) Pharmacognosy I Mosul University/ College of Pharmacy L.A. Dilbreen Barzanji

Pentacyclic triterpenoid saponins This particular class of saponin essentially contains the sapogenin component with pentacyclic triterpenoid nuecleus, that is eventually linked with either sugar or uronic acids. The sapogenin may further may be further classified into three major categories namely: α- amyrin, β-amyrin and lupeol.

Plant materials oftain contain these these saponins in considerable amounts. Thus, primula root contains about 5-10%; liquorice root about 2-12% of glycerrhizic acid (and a correspondingly larger amount of glycerrhizin, the potassium calcium salt); quillaia bark up to about 10% of the mixture known as ‘commercial saponin’ ; the seeds of horse chestnut up to 13% of aescin. As some plants contain more than one saponin and purification is often difficult.

Liquorice root The pharmacopoeial drug is now defined as the dried unpeel or peeled, whole or cut root and stolons of Glycerrhiza galbra. In Western Europe liquorice is cultivated, but the ‘Russian’ and ‘Persian’ drugs are obtained from wild plants. In China, large-scale cultivation is replacing collection from wild. The underground organs are developed into sufficient extent by the end of the third or fourth year, when they are dug up and washed, some are peeled and cut up into short lengths before drying, but much is now used unpeeled.

Glycerrhiza ows most of its sweet taste to glycerrhizin, the potassium and calcium salts of glycerrhizinic acid. Glycerrhizinic acid is the diglucouronic acid of glycerrhetic (glycerrhetinic) acid, which has a tritepenoid structure.

The yellow colour of liquorice is due to flavonoids, which have antigastric effect, example of liquorice flavonoids: liquirtin. Other active constituents of liquorice are polysaccharides with a pronounced activity on the reticuloendothelial system. e.g. glycerrhzan has been characterized as the representative polysaccharide with immunological activity. The roots also contain about 5-15% of sugars (glucose, sucrose).

Action and uses of liquorice Liquorice has been long been employed in pharmacy as a flavouring agent, demulcent, and mild expectorant. The recognition of the deoxycortecosterone effects of liquorice extracts and glycerrhetinic acid has led to its use for the treatment of rheumatoid arthritis, Addison’s disease and various inflammatory conditions. Unlike cortisone, liquorice may give symptomatic relief from peptic ulcer pain.

It has been reported that glycerrhizin gel can act as a useful vehicle for variuos drugs used topically; not only are the anti-inflammatory and antiviral effects relevant but also glycerrhizin enhances skin penetration by the drug. Excessive consumption of liquorice leads to hypertension and hypokalaemic alkalosis.

Ivy The drug consists of the whole or cut aerial leaves of Hedera helix, collected in the spring. This familiar climber and creeper is widely distributed throughout Europe and Asia.

Important constituent of ivy are saponins involving the pentacyclic triterpenoid genins: hederagenin, bayogenin and oleanolic acid. The BP/EP requires a minimum concentration of 3.0% heteracoside C. Like most saponins, those of ivy are toxic in excess causing diarrhea, vomiting and allergy.

Uses of ivy Ivy-leaf extract have been traditionally used as an expectorant for the treatment of various chest conditions, such as bronchitis and whooping cough; also for gout and rheumatic pains. Externally ivy is used cosmetically and for a various of skin conditions.

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