Anthracene Glycosides (or Anthraquinone Glycosides)Anthracene glycosides represent a major class of glycosides. They are abundantly found in various dicot plant families, such as: Ericaceae, Euphorbiaceae, Leguminoseae, Lythreaceae, Polygonaceae, Rhamnaceae, Rubiaceae and Verbenaceae to name a few. Interestingly, some monocots belonging to the family Liliaceae also exhibits the presence of anthracene glycosides. Besides, they are also present in certain varieties of fungi and lichens.A plethora of glycosides having their aglycone moieties closely related to anthracene are present in noticeable amounts in a variety of drug substances, for instance: aloe, cascara, frangula, sagrada and senna. These drugs are invariably employed as cathartics.

Phenol GlycosidesA variety of phenol glycosides are widely distributed in nature. It has been found that quite a few simple phenol glycosides have their aglycone portion loaded with either phenolic moieties or more often with alcoholic moieties or carboxylic acid functions. Invariably, the natural vegetative plant products, such as: Willow bark (containing Salicin) and Bearberry leaves (containing arbutin) have been employed therapeutically since ages, the former as antipyretic and the latter both as urinary antiseptic and as diuretic. A few frequently used phenol glycosides commonly found in natural plant products are described below; such as: Arbutin; Gaultherin; Salicin; Populin; Glucovanillin.Steroid GlycosidesSteroid glycosides are also referred to as Cardiac glycosides in many available books on phytochemistry. In fact, there exists enough evidence in literatures to reveal that a host of medicinal plants comprise of cardiac or cardiotonic glycosides, collectively known as steriod glycosides, and they have since been employed as arrow poisons or cardiac drugs. Interestingly, from a therapeutic perspective this particular group of compounds may be regarded as one of the most important of all naturally occurring plant products.The cardiac glycosides are basically steroids with an inherent ability to afford a very specific and poweful action mainly on the cardiac muscle when administered through injection into man or animal. As a word of caution, a small amount would exhibit a much needed stimulation on a diseased heart, whereas an excessive dose may cause even death.Generally, the steroid glycosides are invariably employed in the therapeutic domain primarily for two vital reasons, namely: (a) to enhance the tone, excitability and above all the contractibility of the cardiac muscle; and (b) to increase the diuretic action, due principally to the enhanced renal circulation (an inherent secondary action).A few important plant products belonging to this category are discussed in the sections that follows, namely:Flavonoid GlycosidesFlavonoid constitute one of the largest class of naturally occuring plant products mostly phenols either in the free state or as their respective glycosides. As the very name suggests they are usually yellow-coloured compounds (flavous is a latin word yellow colour). Interestingly, more than 2000 different chemical compounds have been isolated, identified and reported from plant sources. In fact, their chemical structures are solely based upon a C6C3C6 carbon skeleton having a pyran or chroman ring bearing a second benzene (aromatic) ring strategically positioned at C2, C3 or C4 as shown below:

In nature they are invariably available as: flavones, flavanones, flavonols, isoflavones, and anthocyanidins*. In certain specific instances either the 6-membered heterocyclic ring (pyrones) is replaced by a 5 membered heterocyclic ring (aurones) or exists in an open-chain isomeric form (chalcones). Besides, the normally existing glycosylated derivatives found in nature, other types of derivatives, such as methylated, acetylated, prenylated, or sulphated ones also exist. Nevertheless, it has been established that a large variety of flavonoids exert a wide range of activities in nature, namely: antimicrobial agents, signaling molecules, or stress metabolites.Coumarin and Furanocoumarin GlycosidesGenerally, couramin and its derivativces furanocoumarin are found to be present in a plethora of naturally occuring plants. Nevertheless, the coumarin is presnet either in the free state or its corresponding glycosides form in nature, but it has been observed that the former being most common.2.5.1 Coumarin GlycosidesThese are reported to be present in about 150 different species spreading over to nearly 30 different families, of which a few important ones are, namely: Caprifoliaceae, Leguminosae, Oleaceae, Rubiaeeae, Solaneceae, and Umbelliferae.This basic nucleus of coumarin is considered to be derived from o-hydroxy cinnamic acid (or o-coumarin acid) by its dehydration to yield the fused lactone ring as shown below:It has been observed that invariably most naturally occurring coumarins essentially bear an oxygen atom either as hydroxyl (OH) or alkoxyl (OCH3 or OC2H5) at C-7 position.A few important naturally occurring coumarin glycosides along with their respective biological sources have been summarised in Table 4.3.2.5.1.1 Coumarin Coumarin is abundantly found in a variety of natural products which are used profusely as a flavouring agent in pharmaceutical preparations.Synonyms Tonka bean camphor; Cumarin; Coumarimic anhydride.2 Furanocoumarin GlycosidesIn general, the furanocoumarins are obtained by the fusion of the furan ring to the coumarin nucleus either at C-6 and C-7 positons or at C-7 and C-8 positions. A few typical examples belonging to this class of glycosides are discussed in the sections that follows, namely: Khellolglucoside; Psoralea; and CantharidesCyanogenetic GlycosidesThe cyanogenetic glycosides are named so because they yield either hydrocyanic acid upon hydrolysis or they essesntially possess a hydrocyanic acid in the aglycone moiety. They are also designated as cyanophore glycosides. Interestingly, about 110 families belonging to the plant kingdom have been reported to contain the cyanogenetic glycosides; however, Rosaceae being the most prominent one amongst them.It is pertinent to mention here that cyanogenetic glycoside containing drug substances, as such do not exert any specific therapeutic activity, but they are invariably employed as viable pharmaceutical aids, such as: flavouring agents.A large number of cyanogenetic glycosides were isolated and identified from various plant sources, namely: Linamarin, Linustatin, Lotaustralin and Lucumin as shown in Table 4.5.A few important examples of naturally occurring drug substances containing cyanogenetic glycosides shall be discussed here, namely; Bitter almond, Wild cherry bark and Linseed. These drugs shall be discussed in the pages that follows:

Bitter GlycosidesIn general, bitters are the edible natural products mostly consumed before any normal meals to stimulate as well as enhance the appetite. However, the bitter glycosides as a class do possess almost similar activities like the bitters such as: digestive, stomachic and febrifuge. Therapeutically, the bitters have been found to exert their stimulant effects on the gustatory (i.e.; related to the sense of taste) nerves located in the mouth and ultimately give rise to an improved gastric juice secretion in the stomach.The bitter glycosides have been found not confined to the same chemical class, but the most important ones amongst them essentially possess the pyran cyclopentane ring.A number of bitter glycosides isolated from natural plants have been put into actual therapeutic practice, namely: Picrorhiza, Gentian, and Chirata, which shall be discussed in the sections that follow.Miscellaneous GlycosidesThere are a number of glycosides which do not fall into the various classifications discussed under Sections 2.1 to 2.10 ; therefore, they have been grouped together under the present head i.e., Miscellaneous Glycosides A few imortant members of this group shall be described here briefly.Steroidal Alkaloidal GlycosidesThey are sepecifically abundant intwofamilies, namely:LiliaceaeandSolanaceae. Just like saponins, thesteroidal alkaloidal glycosidesdo possess significant haemolytic activitiesAntibiotic GlycosidesStreptomycin is the glaring example of an antibiotic glycosides produced by the soil Actinomycete, Streptomyces griseus (Krainsky) Waksman et Henrici belonging to family Actinomycetaceae. It is usually formed by the combination of the genin Streptidine a nitrogen containing cyclohexane derivative and Stretobiosamine a disaccharide representing two-thirds of the streptomycin molecule, through a glycosidic linkageSaponin GlycosidesIn general a group of plant glycosides commonly referred to as saponin glycosides, usually share in different extents, the following two specific characteristics namely:(a) They produce foam in aqueous solution, and(b) They cause haemolysis of Red Blood Corpuscles (RBC).The saponin glycosides are broadly regarded as haemotoxic in nature by virtue of the fact thatthey afford the haemolysis of erythrocytes, which render most of them as fish poisons. Invaribaly, they possess a bitter and acrid taste, besides causing irritation to mucous membranes. They are mostly amorphous in nature, soluble in alcohol and water, but insoluble in non-polar organic solvents like benzene, n-hexane etc.Interestingly, the naturally occurring plant materials consisting of saponin glycosides have been extensively employed in various parts of the globe for their exclusive detergent characteristics, for instance: In South Africa the bark of Quillaia saponaria belonging to family Rosaceae and in Europe the root of Saponaria officinalis belonging to family Caryophyllaceae.SapogeninsThe aglycone of the saponin glycosides are collectively known as sapogenins. Sapotoxinsthe harmful and poisonous sapogenine/ saponins are aften referred to as sapotoxins. Based on the nature of the aglycone residue present in the saponin glycosides, they are broadly classified into the following two categories, namely:(i) Tetracyclic triterpenoid saponins (or Steroidal saponins), and(ii) Pentacyclic triterpenoid saponins.These two categories of saponin glycosides will be discussed with suitable examples from plant sources in the sections that follows:2.8.1 Tetracyclic Triterpenoid Saponins (or Steroidal Saponins)Due to the enormous pharmaceutical importance a plethora of plants have been screened thoroughly for the detection of steroidal saponins. They are not only confined to monocot plants but also extended to dicot plants, such as:Monocot Plants : FamilyAmaryllidaceae, Dioscoreaceae and LiliaceaeDicot Plant : FamilyApocynaceae, Leguminosae and Solanceae1 DioscoreaSynonyms Rheumatism root; Yam.Biological Source It essentially comprises of the dried tubers of Dioscorea delitoidea Wall., Dioscorea tokora Makino, and Dioscorea composita and other species of Dioscorea belonging to the family Dioscoreaceae.DescriptionColour : Slightly brownOdour : OdourlessTaste : Bitter and acridSize : Varies dependig on the actual age of the rhizomes (tubers)Chemical Constituents The major active constituent of dioscorea is diosgenin usually present in the range of 4-6%. Diosgenin is the aglycone of saponoin dioscinBesides, the rhizomes contain starch to the extent of 75% but it has no edible utility because of its bitter taste. They also contain phenolic compounds and an enzyme sapogenase.Uses1. Dioscorea is mostly employed in the treatment of rheumatic arthritis.2. Dioscorea has a tremendous potential as a commercial product because of its high content of diosgenin, which in turn is invariably employed as a starting material for the synthesis of a host of important therapeutic drugs, for instance: sex-hormones, oral contraceptives and several corticosteroids.Pentacyclic Triterpenoid SaponinsThis particular class of saponin essentially contains the sapogenin component with pentacyclic triterpenoid nueleus, that is eventually linked with either sugars or uronic acids. It is pertinent to mention here that the sapogenin may be further classified into three major categories namely: -Amyrin, -Amyrin and Lupeol.GinsengSynonyms Panax; Energofit; Pannag; Ninjin.Biological Source Ginseng is the dried root of different naturally occurring species of Panax, namely: Panax ginseng C.A. Mey or Aralia quinquefolia Deene & Planch (Korean Ginseng);Panax japonica (Japanese Ginseng); Panax notoginseng (Indian Ginseng) belonging to family Araliaceae.DescriptionColour : Yellowish- brown, white or redOdour : NoneShape : Tuberous and corpulentAppearance : Translucent and bears the stem scars.Chemicals Constitutents Ginseng chiefly comprises of a complex mixture of triterpenoidsaponins which may be either a steroidal triterpene or a pentacyclic related to oleonic acid. However, these glyscosides have been classified into three major heads, namely:(a) Ginsenosides,(b) Panaxosides, and(c) Chikusetsu Saponins.Uses1. In the Chinese system of medicine ginseng is the most favourite remedy for a variety of ailments e.g., as a general tonic, stimulant, carminative and diuretic activities.2. It also possesses adaptogenic (antistress) properties and is found to exert positive action on the metabolism, the endocrine system and the central nervous system.3. In the orient ginseng is used abundantly in the treatment of anaemia, diabetes, insomnia, gastritis, neurasthenia and specifically to cure sexual impotence.4. It is found to enhance the natural resistance (i.e., non-specific resistance) and increases the ability to overcome both exhaustion or illness to a great extent.5. It prolongs the life of elderly persons and cures giddiness.2.8.2.2 LiquoriceSynonyms Glycyrrhiza; Liquorice root; Glycyrrhizae radix.Biological Sources Liquorice is the dried, peeled or unpeeled, roots, rhizome or stolon of Glycyrrhiza glabra Linn., invariably known in commerce as Spanish liquorice, or of Glycyrrhiza glabra Linne. var Glandulifera Waldstein et Kitaibel, mostly known in commerce as Russian liquorice, or of other varieties of Glycyrrhiza glabra Linne., which produce a sweet and yellow wood, belonging to family Leguminosae.DescriptionColour : Unpeeled Liquorice-Externally, yellowish brown or dark brown; and internally, yellowish colourOdour : Faint and characteristicTaste : SweetSize : Length = 20 to 50 cm; Diameter = 2 cmShape : Unpeeled drugStraight and nearly cylindricalPeeled drugMostly angularFracture : Fibrous in bark; and splintery in the wood.Chemical Constituents Glycyrrhiza (liquorice) comprises of a saponin like glycoside known as glycyrrhizin (or glycyrrhizic acid)Chemical Tests1. When sulphuric acid (80%) is added to a thick section of the drug or powder, it instantly produced a deep yellow colour.Substituents/Adulterants Glycyrrhiza uralansis, also known as Manchurian Liquorice, which is pale chocholate brown in appearance having wavy medullary rays and exfoliated cork is mostly used as an adulterant for G. glabra. This particulr species is from sugar, but contains glycyrrhizin. Sometimes, the Russian Liquorice is also used as an adulterant, because the drug is purplish in appreance, has long roots but having no stolons.Uses1. Glycyrrhiza has demulscent and expectorant properties2. It is used as a masking agent for bitter drugs in pharmaceutical formulations, such as: quinine, aloe, ammonium chloride etc.3. Ammoniated glycyrrhiza is employed as a flavouring agent in beverages, pharmaceuticals and confectionary.4. The inherent surfectant activity due to the presence of saponins helps to facilitate the absorption of poorly absorbed drugs, for instance: anthraquinone glycosides.5. It is invariably added to beer to form stable and enhanced foaminess.6. It imparts a distinct and characteristic bitter tastte to a number of beverages, such as: stout, root beer and porter.BacopaSynonyms Herpestis; Brahmi.Biological Sources It comprises of the fresh stems and the fresh leaves of Bacopa monnieri Linn., Pennell or Bacopa monnniera Wettst., or Herpestis monniera Linn., H.B. & L., belonging to family Serophulariaceae.DescriptionColour : GreenOdour : NoneTaste : BitterSize : Length = 1.2-1.8 cm; Breadth = 2.5-10 mmShape : Leaves sessile, broad, entire, ovate-oblong or spathulate with black spots.Chemical Constituents The leaves contain saponin glycosides known as bacoside A and bacoside B which on acid hydrolysis give rise to triterpenoid aglycone termed as bacogenin A and bacogenin B respectively. It also contains asiatic acid and brahmic acid as depicted below:6 Cyanogenetic GlycosidesThe cyanogenetic glycosides are named so because they yield either hydrocyanic acid upon hydrolysis or they essesntially possess a hydrocyanic acid in the aglycone moiety. They are also designated as cyanophore glycosides. Interestingly, about 110 families belonging to the plant kingdom have been reported to contain the cyanogenetic glycosides; however, Rosaceae being the most prominent one amongst them.It is pertinent to mention here that cyanogenetic glycoside containing drug substances, as such do not exert any specific therapeutic activity, but they are invariably employed as viable pharmaceutical aids, such as: flavouring agents.Bitter AlmondSynonym Amygdala amara.Biological Source Bitter almond comprises of the dried ripe kernels of Prunus amygdalus Batsch. Var amara (DC) Focke; Prunus communis Arcang., P. amygdalus Bail; and Amygdalus communis Linn., belonging to family Rosaceae.Geographical Source Bitter almond trees are mostly native of Persia and Asia Minor. They are also cultivated in the cooler parts of Panjab and Kashmir, Italy, Sicily, Portugal, Spain, Southern France and Morocco.DescriptionColour : BrownOdour : No specific odourTaste : BitterChemical Tests The general tests of the cyanogenetic glycosides by means of microchemical reactions in naturally occurring crude drugs are based on their hydrolysis to yield hydrocyanic acid. In fact, there are four speciifc and characteristic reactions to detect the presence of liberated HCN, namely:1. Ferriferrocyanide Test: Macerate 1 g of the powdered drug with 5 ml of alcoholic KOH (5% w/v) for five minutes. Transfer it to an aqueous solution containing FeSO4 (2.5 %w/v) and FeCl3 (1% w/v), and maintain at 60-70C for 10 minutes. Now, transfer the contents to HCl (20%) when the appearance of a distinct prussian blue colour confirms the presence of HCN.2. Precipitation of Hg from HgNO3: The reduction of aqueous mercurous nitrate solution (3% w/v) to metallic Hg by HCN being observed by an instant formation of black metallic Hg in the cells.3. Grignard Reaction Test: First of all, dip a strip of white filter paper into a solution of picric acid (1 % w/v in water) drain and then dip into a solution of sodium carbonate (10% w/v in water) and drain. Now, place the crushed and moistened drug material in a small Erlenmeyer flask, and subsequently suspend the strip of the prepared sodium picrate paper above the material and stopper the flask with an air tight cork. Maintain the flask in a warm place for 1 hour when the liberated HCN would turn the sodium picrate paper from its original yellow colour to brick red colour due to the formation of sodium isopurpurate (Grignards Reaction).4. Cuprocyanate Test: First of all, saturate pieces of filter paper in a freshly prepared solution of guaic resin dissolved in absolute ethanol and allow them to dry completely in air. Now, carefully moisten a piece of the above paper with a very dilute solution of CuSO4 and place it into contact with a freshly exposed surface of the drug. In case, HCN is generated, it will give rise to a distinct stain on the paper.Uses1. Bitter almonds are employed as sedative due to HCN content.2. The fixed oil of bitter almond finds its use as demulscent in skin-lotion.3. It is also employed in the preparation of amygdalin and bitter almond water.Black Mustard

Synonym Brown Mustard.Biological Sources These are dried ripe seeds of Brassica nigra Linn., Koch or Brassica juncea Linn, Czern & Coss, belonging to family Cruciferae.DescriptionColour : Black, dark brown or reddish brownOdour : Whole seed-none; Crushed seed-pungent characteristic odour.Taste : BitterSize : Approx. 0.9-1.0 mm in diameterShape : Mostly spherical in shapeSpecial Features Seeds are normally covered with a brittle testa and the kernel is oily and greenish yellow in colour. The approx. weight of 100 seeds ranges between 150 to 170 mg.Chemical Constituents The black mustard seed contains a thioglycoside i.e., a -glucopyranoside termed as sinigrin.Coumarin and Furanocoumarin GlycosidesGenerally, couramin and its derivativces furanocoumarin are found to be present in a plethora of naturally occuring plants. Nevertheless, the coumarin is presnet either in the free state or its corresponding glycosides form in nature, but it has been observed that the former being most common.2.5.1 Coumarin GlycosidesThese are reported to be present in about 150 different species spreading over to nearly 30 different families, of which a few important ones are, namely: Caprifoliaceae, Leguminosae, Oleaceae, Rubiaeeae, Solaneceae, and Umbelliferae.This basic nucleus of coumarin is considered to be derived from o-hydroxy cinnamic acid (or o-coumarin acid) by its dehydration to yield the fused lactone ring as shown below:It has been observed that invariably most naturally occurring coumarins essentially bear an oxygen atom either as hydroxyl (OH) or alkoxyl (OCH3 or OC2H5) at C-7 position.A few important naturally occurring coumarin glycosides along with their respective biological sources have been summarised in Table 4.3.2.5.1.1 Coumarin Coumarin is abundantly found in a variety of natural products which are used profusely as a flavouring agent in pharmaceutical preparations.Synonyms Tonka bean camphor; Cumarin; Coumarimic anhydride.Chemical Structures Coumarin has the following structure:

Uses It is mostly employed as a pharmaceutical aid.2.5.2 Furanocoumarin GlycosidesIn general, the furanocoumarins are obtained by the fusion of the furan ring to the coumarin nucleus either at C-6 and C-7 positons or at C-7 and C-8 positions. A few typical examples belonging to this class of glycosides are discussed in the sections that follows, namely: Khellolglucoside; Psoralea; and Cantharides.2 PsoralenSynonyms Lata-kasturi (Bengali); Bahuchi (Sanskrit).Biological Sources They are the dried ripe fruits of Psoralea corylifolia Linn., belonging to the family Leguminosae. Psoralen is also found naturally in more than two dozen plant sources, namely: Bergernot, Limes, Cloves: family Rutaceae; Figs.: family Moraceae.DescriptionColour : Dark chocholate to blackOdour : Pungent and characteristic after crushing the fruitsTaste : Unpleasant, bitter and acridSize : 3 to 5 2 to 3 mmShape : Pods are ovoid, oblong beam shapedChemical Constituents The fruits of P. corylifolia invariably contain fluorocoumarin compounds known as psoralen and isopsoralenBesides the fruit contains a variety of other chemical constituents, for instance: fixed oil (10%); resin (8.9%); essential oil (0.05%) and small amounts of raffinose and a pigment.Chemical Tests (For Psoralen)1. To a small amount of drug add a minimum quantity of alcohol for complete dissolution. Add to this 3 volumes of propylene glycol, 5 volumes of acetic acid and 43 volumes of water and shake well. The appearance of a blue fluorescence under UV-light indicates its presence.2. The drug is dissolved in minimum amount of alcohol and on addition of a little sodium hydroxide solution exhibits a yellow fluorescence in UV-light.Uses1. The seeds are recommended in leprosy, leucoderma and other skin manifestations. They are also used for snake bite and scorpion sting.2. The oleroesin extracts of seeds are employed to cure leucoderma patches.3. The seeds also find their use as stomachic, anthelmintic, diuretic and diaphoretic.4. It is used orally as a laxative.Flavonoid GlycosidesFlavonoid constitute one of the largest class of naturally occuring plant products mostly phenols either in the free state or as their respective glycosides. As the very name suggests they are usually yellow-coloured compounds (flavous is a latin word yellow colour). Interestingly, more than 2000 different chemical compounds have been isolated, identified and reported from plant sources. In fact, their chemical structures are solely based upon a C6C3C6 carbon skeleton having a pyran or chroman ring bearing a second benzene (aromatic) ring strategically positioned at C2, C3 or C4 as shown below:

In nature they are invariably available as: flavones, flavanones, flavonols, isoflavones, and anthocyanidins*. In certain specific instances either the 6-membered heterocyclic ring (pyrones) is replaced by a 5 membered heterocyclic ring (aurones) or exists in an open-chain isomeric form (chalcones). Besides, the normally existing glycosylated derivatives found in nature, other types of derivatives, such as methylated, acetylated, prenylated, or sulphated ones also exist. Nevertheless, it has been established that a large variety of flavonoids exert a wide range of activities in nature, namely: antimicrobial agents, signaling molecules, or stress metabolites. The structures of a few typical flavonoids are represented here as follows:---------------------------------------------* Anthocyanidins are the colored aglycones found as a large number of pigments from flowerd and fruits (Gr. Antho flower + Gr. Kyanos, blue). Investigations of these pigments were initiated by Willstatter in 1914 and later on extended by Karner R Robinson, GM Robinson and others.4 StrophanthusSynonyms Semino stropanthi.Biological Source These are the dried and ripe seeds of Strophanthus hispidus De*, or of Strophanthus kombe Oliver, belonging to the family Apocynaceae, deprived of the awns.DescriptionColour : Greyish green to light yellowish brownOdour : Slight unpleasantTaste : BitterSize : Length 1- 2 cm; Breadth = 3-5 mm; Thickness = 2 mmShape : Lanceolate to linear-lanceolate, acute at the apex, rounded or blunt at the baseWeight : For 100 seeds 3-4 gSpecific : On treating with 80% H2SO4 the endosperm exhibits a deep feature Emerald green colour.Chemical Constituents The seeds of strophanthus usually contain three vital glycosides, namely:K-strophanthoside, K-strophanthride b and cymarin. Interestingly, all these glycosides undergo hydrolysis to yield strophanthidin.Chemical Tests1. Generally, the strophanthus glycosides exhibit an emerald green colouration on the addition of sulphuric acid.2. Dissolve about 0.1g of strophanthin in 5 ml of water and add to it a few drops of ferric chloride solution followed by a 1-2 ml of concentrated sulphuric acid; the appearance of an initial red precipitate that finally turns green within a period of 1-2 hours.3. To 50 mg of strophanthin add 5 ml of water, shake and add 2 ml of 2% tannic acid solution, the appearance of a distinct precipitate affirms its presence.4. It shows positive Baljet Test, Legal Test and Keller Killiani Test (see Section 2.3.1).Uses1. It is used intravenously for treating emergency cardiac conditions. However, orally strophanthin is not so active.2. These glycosides have been found to exert less cumulative effect unlike the digitalis glycosides.3. Overall their therapeutic actions are very much similar to those of Digitalis.SquillA survey of literature reveals that the Squill bulbs was thoroughly and repeatedly investigated since 1879. However, Stoll in 1933 was first able to separate and isolate two glycosides in their purest form, namely: Scillaren A and Scillaren B. These two naturally occurring glyosides are usually present in the crude drug in the ratio 2:1 (i.e., 2 parts of Scillaren A and 1 part of Scillaren B). Generally, the squill is available in three varieties, namely:(a) European Squill(b) Indian Squill, and(c) Red Squill.2.3.3.1 European SquillSynonyms Sea, onion, Bulbus Scillae; Meerzweibel, White Squill, Squill bulb; Scila.Biological Source European squill is the fleshy inner bulb scales of the white variety of Urginea maritima (L.) Baker (Scilla maritima L.) belonging to family Liliaceae.DescriptionColour : White; Whitish yellow;Taste : Bitter and gummy;Size : Length = 3.5-5 cm; Width = 5-8 mm; Thickness = 2-5 mm;Shape : Available as strips with tapering both ends.Chemical Constituents Squill has the following glycosides, namely:Glucoscillaren A = Scillarenin + Rhamnose + Glucose + Glucose;Scillaren A = Scillarenin + Rhamnose + Glucose;Proscillaridin A = Scillarenin + Rhamnose.Uses1. It is a potent cardiotonic without having any cumulative effect (unlike Digitalis).2. It is mostly employed in small doses as an effective expectorant specially in chronic bronchitis.3. It causes emesis in relatively higher doses.4. The squill glycosides usually produce copious diuresis.5. By virtue of the fact that the squill glycosides possess high therapeutic index and rapid elimination they invariably maintain compensation in such patients where a prolonged treatment is required.2.3.3.2 Indian SquillSynonyms Scilla; Sea onion; Jangli Pyaj; Urginae.Biological Source Indian squill comprises of the dried slices of the bulbs of Urginbea indica Kunth; belonging to the family LiliaceaeDescriptionColour : Yellowish to WhiteOdour : Slight and characteristicTaste : Acrid, bitter and mucilaginousSize : Length = 30-60 cm; Breadth = 3-8 mmShape : Usually 4 to 8 slices are placed one on the top of other and gives it a curved shape.Chemical Constituents Indian Squill essentially comprises of cardiac glycosides (0.3%), alcohol soluble extractives (20-40%), mucilages (40%) and calcium oxalate.The two major cardiac glycosides present in the drug are Scillaren A and Scillaren B (see Section 2.3.3.1).Substituents/Adulterants The bulbs of different species of Ledebouria (Scilla, Linn) are sold in the Indian bazars, under vernacular names which are equivalent to small squill.Ledebouria hyacinthoides, is used as a substitute for squill. It has a scaly bulb, about the size and shape of a small pear, composed of very amooth and fleshyscales, which are so imbricated that they might be mistaken for entire coats if not carefully examined.Uses1. It is largely employed as a cardiotonic , stimulant and also an expectorant.2. It is used as a very effective expectorant both in asthma and chronic bronchitis.3. It possesses anticancer activity against human epidermoid carcinoma of the masopharynx in tissue culture.4. It is in no way a perfect replacement for Digitalis since it possesses not only irritant effect but also is very poorly absorbed systemically.Anthracene Glycosides (or Anthraquinone Glycosides)Anthracene glycosides represent a major class of glycosides. They are abundantly found in various dicot plant families, such as: Ericaceae, Euphorbiaceae, Leguminoseae, Lythreaceae, Polygonaceae, Rhamnaceae, Rubiaceae and Verbenaceae to name a few. Interestingly, some monocots belonging to the family Liliaceae also exhibits the presence of anthracene glycosides. Besides, they are also present in certain varieties of fungi and lichens.A plethora of glycosides having their aglycone moieties closely related to anthracene are present in noticeable amounts in a variety of drug substances, for instance: aloe, cascara, frangula, sagrada and senna. These drugs are invariably employed as cathartics.2.1.1 AloesSynonym: AloeBiological Source: Aloe is the dried latex of leaves of various species of Aloes, namely:Aloe barbadensis Miller (or Curacao Aloe);Aloe ferox Miller (or Cape Aloe);Aloe perryi Baker (or Socotrine Aloe);Aloe africana Miller and Aloe spicata Baker (or Cape Aloe).All these species belong to the family Liliaceae.Chemical Tests The overall chemical tests for aloes may be divided into two separate heads, namely: (a) General Tests, and (b) Special Tests(a) General Tests: For this prepare a 0.1% (w/v) aqueous solution of aloes by gentle heating, add to it 0.5g of Kiesulgur and filter through. Whatman Filter Paper No. 42 and preserve the filtrate for the following tests:1. Borax Test (or Schoentetens Reaction): To 5 ml of the above test solution add 0.2 g of pure borax and heat gently till it gets dissolved. Transfer a few drops of the resulting solution into a test tube filled with distilled water, the appearance of a green coloured fluoroscence due to the formation of aloe emodin anthranol shows its presence.2. Bromine Test: When equal volumes of the test solution and bromine solution are mixed together, it yields a pale-yellow precipitate due to the production of tetrabromaloin.3. Modified Borntragers Test: It is known that aloin (or barbaloin) belongs to the class of Cglycoside which does not undergo hydrolysis either by heating with dilute acid or alkali, but it may be decomposed with ferric chloride due to oxidative hydrolysis. Hence, the Modified Borntragers test employing FeCl3 and HCl is used as stated below:First of all heat together 0.1 g of powdered aloe with about 2 ml of FeCl3 solution(5% w/v) and 2 ml of dilute HCl (6N) in a test tube over a pre-heated water bath for 5 minutes. Cool the contents and extract the liberated anthraquinone with carbon tetrachloride. Now carefully separate the lower layer of CCl4 and add to it ammonia solution. The appearance of a rose-pink to cherry red colour confirms its presence.Rhubarb

Synonyms: Rheum; Radix rhei; Rhubarb rhizome.Biological Source: Rhubarb is the rhizome and roots of Rheum officinale Bail., R. palmatum L., Rheum emodi Wall ; R. webbianum Royle, belonging to the family Polygonaceae. The rhizome and roots are mostly collected from 6-7 year old plants just prior to the following season. They are commercially available either with intact cortex or partially decorticated.Chemical Constituents Rhubarb essentially contains mainly the anthraquinone glycosides and the astringent components. The former range between 2 to 4.5% and are broadly classified into four categories as stated below:(a) Anthraquinones with COOH moietye.g., Rhein; Glucorhein(b) Rhubarb in addition to the above constituents, consists of rheinolic acid, pectin, starch, fat and calcium oxalate. The calcium oxalate content ranges between 3-40% in various species of rhubarb which reflects directly on the corresponding ash values (i.e., total inorganic contents).(c) Chemical Tests(d) 1. The Rhubarb powder on being treated with ammonia gives rise to a pink colouration.(e) 2. Rhubarb gives a blood-red colouration with 5% potassium hydroxide.(f) 3. It gives a positive indication with modified Borntragers test (see under Aloes).(g) Uses(h) 1. It is used mainly in the form of an ointment in the treatment and cure of chronic eczema, psoriasis and trichophytosisas a potent keratolytic agent.(i) 2. It is employed as a bitter stomachic in the treatment of diarrhoea.(j) 3. It is also used as a purgative.(k) 2.1.3 Cascara Sagrada(l) Interestingly, the very name cascara sagrada is Spanish for the sacred bark; Rhamnus is the ancient classical name for buckthorn, and Purshianus was attributed as a mark of honour and respect to the great German botanist Friedrich Pursch.(m) Synonyms Sacred bark; Chitten bark; Chittin bark; Purshiana bark; Persian bark; Bearberry bark;Bearwood; Cascara bark; Cortex Rhamni purshianae.(n) Biological Source Cascara sagrada is the dried bark of Rhamanus purshiana DC., belonging to(o) family Rhamnaceae, from which a naturally occurring cathartic is extracted. It is usually collected at least one year prior to its use.(p) Description(q) Colour : Outside-purplish brown; Inside reddish brown.(r) Odour : A typically nauseatic odour.(s) Taste : Persistently bitter.(t) Size : Occurs in varying sizes of thickness between 1 to 4 mm.(u) Shape : Mostly occurs in quills or channels. Also available in small, flat and broken segments.(v) Chemical Constituents The cascara sagrada bark is found to contain two major types of anthracene compounds, namely:(w) (a) Normal O-Glycosides These are based on emodin like structures and constitute about 10 to 20% of the total glycosides, and(x) (b) Aloin-like C-Glycosides These comprise of about 80 to 90% of the total glycosides.(y) The two C-glycosides are known as barbaloin and deoxybarbaloin (or chrysaloin) as given below:(z) Chemical Test It gives a positive indication with Modified Borntragers test because of the presence of C-glycosides.(aa) Substituents/Adulterants The barks of Rhamanus californica and R. fallax are generally used as a substitute for cascara sagrada bark. Sometimes the frangula bark is also used as a substitute for this drug. However, the former types of barks (Rhamnus species) exhibit a more uniform coat of lichens along with broader medullary rays when compared to the original drug species.