Carbohydrates Definition of :A sugar is a that is soluble in water are usually crystalline and have a sweet taste. Chemicals that are sugars often have names ending in "-ose". For example, note the suffix "-ose" in , , , , , and . The word-ending "-saccharide" does not necessarily indicate that the chemical or group or category of chemicals is a sugar.

Definition  are polyhydroxy aldehydes, or ketones or substances that hydrolyze  polyhydroxy aldehydes & ketones.

They usually contain H & O in the same ratio as in H2O (2:1).

 Thus, the name “carbohydrates” indicates that these compounds are “hydrates of carbon”.

Carbohydrates have the general formula:

Cx(H2O)Y where X = Y e.g. C6(H2O)6

••Exceptions: 1- Deoxy sugars ex: C6H12O5 2- Certain non carbohydrates ex: Acetic acid Earlier the name "carbohydrate" was used in chemistry for any compound with the formula Cm(H2O)n. Following this definition, some chemists considered formaldehyde CH2O to be the simplest carbohydrate, while others claimed that title for . Today the term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons. Natural saccharides are generally built of simple carbohydrates called with general formula

(CH2O)n where n is three or more.

They may be an aldehyde or ketone with many hydroxyl groups added, Examples of monosaccharides are glucose, fructose and . However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., uronic acids and deoxy-sugars such as Rhamnose, Cymarose, Digitoxose), and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g., formaldehyde CH2O and inositol (CH2O)6).

The open-chain form of a often coexists with a heterocyclic compound|closed ring form where the aldehyde/ketone carbonyl group carbon (C=O) and hydroxyl group (-OH) react forming a hemiacetal with a new C-O-C bridge. Monosaccharides can be linked together into what are called (or ) in a large variety of ways.

Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, , a component of DNA, is a modified version of ; is composed of repeating units of N-acetylglucosamine, a nitrogen-containing form of glucose. Classification of Carbohydrates according to the number of sugar units

Monosaccharides Oligosaccharides Polysacccharides

Formed of 1 sugar unit Yield 2 to 10 Yield > 10 cannot be hydrolyzed monosaccharides monosaccharides to simpler carbohydrates on hydrolysis on hydrolysis Oligosaccharides Chemical Structure: Oligosaccharides consist of a small number of monosaccharides joined together. Some sources say that oligosaccharides consist of 2-10 monosaccarides but as chemicals whose molecules that consist of two monosaccharides joined together are . But not very many (as in long chains) of monosaccharide units joined together (because many monomers joined together forming long chains are polymers, in this case polysaccharides. Remember: "Oligo" "Few" or in some cases "deficiency", i.e. too few(. Characteristics: •In many cases only partially digestible by humans. •The undigested part of oligosaccarides may help support intestinal microflora (i.e. microorganisms living in the digestive tract, many of which perform useful functions, though under certain conditions some species are considered potentially harmful). Some studies have indicated that FOS or GOS can increase the quantity of "friendly bacteria" in the colon while also reducing the quantity of harmful bacteria. Types of Oligosaccharides :

•1-Fructo-oligosaccharides (FOS)

•Chemically, consist of short chains of fructose molecules •Present in certain plants e.g. some artichokes, chicory, leeks, onions. •Can also be synthesized by enzymes of the fungus Aspergillus niger acting on sucrose. •2-Galacto-oligosaccharides (GOS)

•Chemically, consist of short chains of galactose molecules •Naturally occurring in soybeans •Can be synthesized from lactose (a ) Continue Types of Oligosaccharides :

•3-Mannan Oligosaccharides(MOS)

•Used in some animal feeds - for digestive health, energy, & performance •Unlike other oligosaccharides, MOS are not fermentable Polysaccharides

Chemical Structure: Polysaccharides consist of polymers of chains (in some cases very long chains) of monosaccharide or disaccharide units all joined together. Remember: "Poly" "Many" Characteristics: •Tasteless •Insoluble in cold water Main Groups of Polysaccharides : 1- •Chemically, consists of long chains of glucose (a monosaccharide) molecules •Formed by plants during photosynthesis •Present in many plant-based food sources, such as root vegetables. e.g. potatoes, cereals e.g. and pulses. 2- •Formed when starchy foods (i.e. foods that contain starch, such as bread or potatoes) are baked or toasted. Dextrin is more soluble than starch 3- •Chemically, consists of long chains of glucose (a monosaccharide) molecules •Forms the structure of some plants •Indigestible by humans but digestible by some other animals. •Valuable in human diet as source of dietary fibre- which used to be known as "roughage" Continue Main Groups of Polysaccharides 4- •Present in the roots and/or fruits of certain plants e.g. types of plums and apples •Pectin forms a gel in water and has uses for setting jam and making various sweet foods. •Sometimes used as a vegan alternative to gelatin (also known as gelatine) in the preparation of "set" or glazed foods because the beef (cow) or pork (pig) origin of gelatin is not acceptable to some people. •Pectin forms a complex 5- •The stored form of glucose (glucose is a monosaccharide) present in animals including humans. •Energy store within the body, stored within muscles, the liver and brain •Humans store sufficient glycogen for 24 hours. Monosaccharides

● Three carbons =

● Four carbons =

● Five carbons =

● Six carbons =

Aldoses: are monosaccharides with an aldehydic group & many hydroxyl (-OH) groups

Ketoses: are monosaccharides with a ketonic group & many hydroxyl (-OH) groups

Classification of M onosaccharides

According to number According to type of of carbon atoms carbonyl group they contain

Trioses Glyceraldehyde Glucose , Galactose M annose Fructose , , Apiose

Hexoses Glucose, Galactose, M annose, Fructose Classifications of Oligosaccharides

According to the number of molecules of simple sugars they yield on hydrolysis

Disaccharides

Raffinose Reducing Non reducing

Sucrose Lactose, Maltose Classification of Polysaccharides

Homopolysaccharides Heteropolysaccharides

Polymers of more than one Polymers of a single type of monosaccharide or monosaccharide of monosaccharides + sugar derivatives Starch Cellulose Gums Mucilages Agar Algin Pectic substances Physical Properties of Carbohydrates  Condition: Monosaccharides & most disaccharides are white, crystalline & with sharp melting points.

 Taste: Most of the simple & low molecular weight sugars have a sweet taste.

 Solubility: Monosaccharides are soluble in cold water & hot alcohol. Gums are soluble in water & insoluble in alcohol. Starch, glycogen, Inulin, pectin & mucilages are more soluble in hot than cold water & insoluble in alcohol. Pentosans, , & are insoluble in cold & hot water but soluble in dilute alkalis. Cellulose is insoluble in all the previous solvents. Optical activity

Polarimetry = Measurement of optical activity in chiral or asymmetric molecules using plane polarized light  Measurements are carried out in an instrument called “Polarimeter” Rotation is either (+) = Dextrorotatory or (-) = Levorotatory

Mutarotation Existence of 2 pure forms of glucose ( &  ): Pure -glucose has a specific rotation of +112o & pure -glucose has a specific rotation of +18.7o

Interconversion between the - & - anomers: When either form of glucose is allowed to stand in aqueous solution (aged), the specific rotation of the solution slowly changes to + 52.7o

“” = change in specific rotation observed on standing (aged), in a sugar solution (reducing) & produced as a result of equilibration between the 2 anomers ( & ) & the aldehydic form. Mutarotation

H OH HO H C CHO C 1 1 1 H OH H OH H OH HO H HO H HO H H OH H OH H OH 5 5 5 H O H OH H O 6 CH OH 6 2 6 CH2OH CH2OH

-D-glucose D-Glucose -D-glucose D o [] = + 112 Aldehydic form []D = + 18.7o Mutarotation

O H C CH2OH CH2OH H C OH H O H H O OH H H OH H HO C H OH H OH OH H C OH OH H H OH H OH °C H C °OCH [α] D = [α] D = -D-(+)-glucopyranose -D-(+)-glucopyranose CH2OH o []D = + 112o open-chain form of []D = + 18.7 °C D-(+)-glucose [α] D At equilibrium [ α ] ° C = +52.5° [α]°C D Carbohydrates Chemistry D & L Notation  D & L designations indicate the configuration of the –OH group on the chiral carbon farthest away from the carbonyl group i.e. next to the bottom carbon atom 1. If the –OH group points to the right, the isomer is a D-isomer. 2. If it points to the left, the isomer is L. 3. The D form is the isomer usually found in nature. Configuration of glyceraldehyde: The simplest monosaccharide, which contains only one chiral center, is glyceraldehyde (reference sugar) & it exists in 2 enantiomeric (21 = 2) mirror image forms CHO CHO CHO

CHOH * OH * H HO H CH2OH CH2OH CH2OH Glyceraldehyde D-Glyceraldehyde L-Glyceraldehyde The D- family of aldohexoses: D (+) glucose has 4 chiral centers & exists as 24 = 16 (2n, n=4) possible stereoisomers (8 for the D & 8 for the L series).

CHO CHO CHO CHO CHO CHO CHO CHO H OH HO H H OH HO H H OH HO H H OH HO H H OH H OH HO H HO H H OH H OH HO H HO H H OH H OH H OH H OH HO H HO H HO H HO H H OH H OH H OH H OH H OH H OH H OH H OH CH OH CH2OH 2 CH2OH CH2OH CH2OH CH2OH CH2OH CH2OH Glucose Galactose Stereochemistry (Types of Isomers) Enantiomers Diastereomers Epimers

H O O H O H O H O H O H C C C C C C HO C* H H C* OH HO C* H H C* OH H C* OH HO C* H H C* OH HO C* H HO C* H HO C* H HO C* H HO C* H HO C* H H C* OH H C* OH HO C* H H C* OH H C* OH HO C* H H C* OH H C* OH H C* OH H C* OH H C* OH CH OH CH2OH 2 CH2OH CH2OH CH2OH CH2OH L-glucose D-glucose D-mannose D-galactose D-glucose D-mannose

Enantiomers are nonsuperimposable mirror images of one another

Pairs of isomers that have opposite configurations Diastereomers at one otwor m ore chiral centers but are NOT mirror images

Epimers Two sugars that differ in configuration at only one chiral center Cyclic Structures

R R C O + R'- OH C OH H H OR' Aldehyde Alcohol Hemiacetal

R R C O + R"- OH C OH R' R' OR'' Ketone Alcohol Hemiketal Cyclic Structures Monosaccharides with 5 & 6 carbon atoms form cyclic structures The hydroxyl group on C-5 reacts (addition reaction  hemiacetal) with the aldehyde group or ketone group at C-1 or C-2

5 O O 5 4 1 2

3 3 2 4 Pyran ring Furan ring Cyclic Structures

1 CHO 2 H OH 3 HO H H H OH H 4 6 1 H OH HOH C CHO 2 5 4 3 2 5 H OH OH OH H OH

6 CH2OH D-Glucose Aldehydic form Linear & cyclic structures of glucose Abbreviated structures of -D-glucose

6 CH2OH O 4 5 1

3 2 The structure is comparatively unstable, but may be stabilised on formation. Fructose in nature, is always in the furanose form, but when isolated in crystalline form, it has a structure.

Glycoside formation Two or more sugars attached together to form one sugar (oligo or polysaccharide) through alpha or beta link. Determination by several methods. One of these is enzymatic hydrolysis : 1-alpha (Maltose) can only hydrolysed by maltase (an enzyme occurs in barely) 2-Beta glycosides (cellulose) can only hydrolysed by emulsin (an enzyme occurs in bitter almond; rosaceous seed) Haworth Structure for D-Glucose –OH groups on the right (C-2, C-4) Down

–OH groups on the left (C-3)  UP

–OH group at C-1 has 2 possibilities: Down   & Up   anomer

Haworth Structure for D-Glucose

CH2OH CH2OH o o OH

OH OH  OH OH OH

OH  OH

-D-Glucose -D-Glucose Anomeric hydroxyl

Anomeric hydroxyl Conclusion: Pyranose & Furanose Structures of Monosaccharides Hexoses do not exist most of the time as straight chain aldehydes or ketones but many evidences indicate the presence of an equilibrium between a straight chain & a cyclic structure.

Reaction between the aldehyde or keto group & the hydroxyl group at C-5 or C-4 result in hemiacetal formation & the cyclic structure is either pyranose (C1-C5) or furanose (C1- C4) or (C2-C5, in case of ketoses). e.g. (α) D-glucopyranose (exists as hemiacetal). (β) D-glucopyranose (exists as hemiacetal). (β) D-fructofuranose (exists as hemiketal).

OH CH2OH CH2OH HOH2C OH O O O OH OH OH H CH2OH OH OH OH OH OH OH

-D Glucopyranose -D Glucopyranose -D Fructofuranose Reactions of Monosaccharides

I-Reactions as II-Reactions as II-Specific reactions alcohols carbonyl comp. I- Reactions as alcohols: A- Ester formation:

1- Using acetic anhydride/ZnCl2 and reflux. 2- To dertermine the no of OHs. 3- All acetylated except that involved in ring eg: Glucose 1, 2, 3, 4, 6- pentaacetyl glucose B- Ether formation:

1- Using MeI/Ag2O OR Me2SO4/Na2CO3. 2- To dertermine the no of OHs. 3- All acetylated except that involved in ring eg: Glucose 1, 2, 3, 4, 6- pentaacetyl glucose

II- Reactions as carbonyl compounds

A-Oxidation reactions Aldoses may be oxidized to 3 types of acids ■ Aldonic acids: Aldehydic group oxidised  carboxyl group (COOH) eg: glucose  gluconic acid ■ Uronic acids: Aldehydic group is maintained intact & primary alcoholic group oxidised  COOH eg: glucose  glucuronic acid eg: galactose  galacturonic acid ■ Saccharic acids (glycaric acids): Oxidation at both ends of the monosaccharide eg: Glucose  Saccharic acid eg: Galactose  Mucic acid eg: Mannose  Mannaric acid

Ketoses are oxidized to give mixture of acids of lower mol. weight

COOH Oxidation of Aldoses H OH HO H H OH D-Gluconic acid O H 2 H OH O r 2, -1 H B C CH OH at 2 C on ati H OH xid O CH █2O █H HO H H OH H OH Controlled oxidation HO H D-Glucuronic acid H OH H OH Oxidation at C-6 CH2OH H OH D-glucose COOH O H xi N COOH da O ti 3 on H OH a t C HO H -1 D-Glucaric acid & H OH C -6 H OH (Saccharic acid) COOH Oxidation of Ketoses

COOH H OH CH2OH H OH + COOH Br2, H2O CH2OH CH2OH Trihydroxy Glycolic acid Mild oxidation O butyric acid HO H 2 monocarboxylic acids H OH

H OH COOH HNO COOH CH2OH 3 H OH + Strong oxidation COOH D-Fructose H OH COOH Succinic acid Oxalic acid

2 dicarboxylic acids Importance of Gluconates Mineral gluconates are used as nutritional supplements (nutraceuticals) & in case of mineral deficiency as they are more easily adsorbed than other mineral salts. They have less gastric distress than inorganic ferrous salts. Examples: ● Calcium Gluconate (Monohydrate) - USP ● Calcium Gluconate (Anhydrous) - USP ● Copper Gluconate- USP ● Ferrous Gluconate – USP ● Magnesium Gluconate - USP ● Manganese Gluconate (Anhydrous) - USP ● Potassium Gluconate (Anhydrous) - USP ● Zinc Gluconate - USP B- Reduction reactions

■ Either done catalytically (hydrogen & a catalyst) or enzymatically

■ The resultant product is a polyol or sugar alcohol (alditol) eg: Glucose  Sorbitol (glucitol) eg: Mannose  Mannitol eg: Fructose  Mannitol + Sorbitol eg: Galactose  Dulcitol

CHO CH2OH 2 CHO CH2OH H OH H OH 2 HO H HO H NaBH HO H 4 HO H NaBH4 4 HO H HO H H OH H OH H OH H OH H OH H OH H OH H OH CH2OH CH2OH CH2OH CH2OH D-glucose Glucitol (Sorbitol) D-Mannose Mannitol

CHO CH2OH CH2OH H OH H OH O Mannitol HO H HO H HO H NaBH4 NaBH4 4 HO H HO H H OH H OH H OH H OH Sorbitol CH2OH CH2OH CH2OH

D-Galactose Dulcitol D-Fructose Uses: Sugar alcohols (Mannitol)

Mannitol is not absorbed from GIT, when administered IV, it is not metabolised and eliminated readily by glomerular filteration (used as osmotic diuretic(

Mannitol hexanitrate used as vasodilator

Uses: Sugar alcohols (Sorbitol)

■ Sorbitol (D-Glucitol) is an atificial sweetener (sugar substitute) and mild laxative

■ Sorbitol is dehydrated  1,4,3,6-dianhydro-D-sorbitol (isosorbide) used as nitrate in treatment of angina

C- Glycoside formation (Acetal Formation ) : Monosaccharides react with one mol. of alcohol or any hydroxyl to give acetals or glycosides Mannose (seeds of date, and coffee) Galactose: several polysaccharide including agar-agar, linseed mucilage produce galactose on hydrolysis. Lactose (D-galactose and D-Glucose) III- Specific reactions A- Reaction with phenylhydrazine (Osazone): An reacts with 3 molecules of phenylhydrazine  crystalline phenylosazone. This results in loss of the chiral center at C-2. The C-2 epimers glucose & mannose  same osazone as fructose, the ketohexose at C-2 H H C O C NNHph Condensation H C OH + NH2NHph H C OH + NH2NHph

(HOHC)3 Phenylhydrazine (HOHC)3 Glucosazone

CH2OH CH2OH Glucose Oxidation H

C NNHph Condensation H NH NHph Galactosazone C NNHph 2 + C NNHph (HOHC)3 C O

CH2OH (HOHC)3

Glucosazone CH2OH Maltosazone Lactosazone B-Reaction with conc. mineral acids: ■ Conc Mineral acids cause dehydration of Monosaccarides to give furfural derivatives.

■ Conc Mineral acids cause hydrolysis followed by dehydration of oligosaccharides and polysaccharides to give furfural derivatives

Furfural derivatives couple with phenols or amines to produce colored compounds Examples eg: α- naphthol Molisch’s test eg: Orcinol Bial’s test

C-Reaction with oxidizing cations: ■ All monosaccharides and reducing oligosaccharieds are easily oxidized with weak oxidizing reagents such as alkaline Cu2+ (Fehling's Reagent) Molisch test:

Bial's test is a chemical test for the presence of pentoses. It is named after Manfred Bial, German Physician.

The components include orcinol, hydrochloric acid, and ferric chloride.

A pentose, if present, will be dehydrated to form furfural which then reacts with the orcinol to generate a colored substance.

The solution will turn bluish and a precipitate may form.

Monosaccharides

Pentoses Hexoses Deoxy sugars

e.g. e.g. Rhamnose Xylose Aldoses Ketoses e.g. e.g. Digitoxose Arabinose Glucose Fructose Apiose Galactose

Mannose Monosaccharides (A) - Pentoses :1-5C, 2-unfermentable by yeast 3- Give furfural when warmed with acids

C H O C H O

H O H O H H O H O O O H H O H O H H O H O H O H H O H O H H O H O H O H C H 2 O H C H 2 O H  - L - a r a b i n o p y r a n o s e  - D - x y l o p y r a n o s e Monosaccharides - Pentoses

Name -L Arabinose  -D-Xylose (Pectin sugar) (Wood sugar) Source Gums Corncobs Pectic substances Bran Hemicelluloses Straw  woody material

Gum arabic

Corncobs Wheat bran Continue: Monosaccharides - Pentoses Name D-Ribose D-Apiose (branched sugar) Source *(component of Obtained by nucleic acid found in hydrolysis of the all plant and animal flavone glycoside, cells) apiin, present in *a constituents of the leaves & seeds several vitamins and of parsley coenzymes

Parsley Continue: Monosaccharides – Pentoses

CHO CHO H OH O H OH O H OH CH2OH CH2OH H H H OH OH OH H H OH OH HO OH HO HOH2C CH2OH CH2OH D-apiose Beta-D-apiose D-Ribose Alpha-D-Ribofuranose (Branched sugar) (Branched sugar) Chemical tests for Pentoses

1.Aniline acetate paper: Pentoses + HCl + D + paper moistened with aniline acetate  red stain (furfural) N:B. methyl pentoses (Rhamnose)  Yellow stain

2.Bial’s test:

Pentoses + Bial's reagent (= Orcinol / HCl) + D  green color

3.Phloroglucinol /HCl:

Pentoses  red color brownish violet precipitate. (B)-Hexoses: 1- Aldohexoses:

CHO CHO CHO

H OH HO H H OH

HO H HO H HO H

H OH H OH HO H

H OH H OH H OH CH OH CH2OH 2 CH2OH D-glucose D-Mannose D-galactose CH OH CH2OH 2 CH2OH HO O O O OH OH HO OH

OH OH OH OH OH OH OH -D-glucose -D-Mannose -D-galactose CH OH CH2OH 2 CH2OH OH OH HO OH O O O OH OH HO OH

OH -D-glucose OH -D-Mannose -D-galactose OH OH D-Glucose (dextrose, grape sugar, corn sugar, blood sugar)

CHO

H C OH CH OH 2 CH2OH O HO C H H H H O OH H H H H C OH OH OH H OH OH OH H H C OH H OH H OH CH OH 2 -glucopyranoside -glucopyranoside D-glucose Preparation:

D-Glucose is commercially prepared from starch by:

Aqueous starch suspension (15-20%)

* Addition of dilute acid (0.03 N HCl) * Autoclaving at 150 oC, 30-35 min (complete hydrolysis) * Neutrali zation with sodium carbonate to pH 4 to 5 * Filtration

Filtrate

* Decolorization with charcoal * Concentration under reduced pressure * Crystallization

Glucose Uses of glucose: 1.Nutrient, given by mouth, enema, or IV. injection. 2.As ingredient in dextrose /saline or Ringer solution injections. 3.Dextrose is used commercially in the manufacture of candy, carbonated beverages, ice cream, bakery products & in the canning industry. Liquid Glucose Colorless, sweet, & water-miscible syrupy liquid. Prepared by partial acid hydrolysis of starch using dilute HCl & heating for 20 min. Consists of a mixture of glucose, maltose, dextrin & water. Used as sweetening agent, as substitute for sucrose & as an excipient in massing pills. 2-Ketohexoses , D-fructose, levulose, -D(-) fructofuranose Fructose

(Fruit sugar)

CH2OH O HOH2C O OH HO H OH H OH H CH2OH H OH OH CH2OH D-Fructose -D Fructofuranose 

Source: Chicory It is found free in honey & in fruits juices, or as constituent of polysaccharide e.g. Inulin. Preparation of fructose ■ From glucose: By the action of NaOH ■ From sucrose: After inversion of aqueous solutions of sucrose then separation of fructose from glucose by treatment with CO2 Ca (OH)2  Ca fructosate precipitate Fructose ■ From Inulin: (A polymer characteristic of certain plants of family Asteraceae e.g. Artichoke & Chicory) by acid hydrolysis. Properties of Fructose

1- (Fehling, Barfoed) 2- Form Osazone

3-Exhibit mutarotation

4-Gives Seliwanoff’s test

Uses of fructose

Fructose is used as food for diabetics (in emergencies of diabetic acidosis) & in infant feeding formulae (being more easily digested than glucose).

3-Deoxy sugars (Desoxy sugars)

A) 2-deoxy sugar B) 6-deoxy sugar C) 2,6-deoxy sugar

2-Deoxy-D-ribose -L-Rhamnose D-Digitoxose D-Cymarose A) 2-Deoxy sugar

1 1 CHO CHO H H HOH C HOH2C 2 O 2 O 2 H H H OH H H H H 2 H OH H OH H OH H OH 4 4 H H OH HO OH H OH HO

CH2OH CH2OH alpha-D-Ribose 2-Deoxy-alpha- D-Ribose 2-Deoxy-D-Ribose D-Ribose B) 6-Deoxy-hexoses (Methyl pentoses) -L-Rhamnose (6-deoxy-L-Mannose) e.g.: Glucoscillaren A, scillaren A and Proscillaridin A in Sqill leaves. Also in Strophanthus seed (Quabain=G- strophanthin)

CHO CHO CHO HO H HO H H OH HO H HO H H OH OH O OH

H OH H OH OH H CH3 H OH H OH OH H OH OH CH2OH CH3 CH3

D-Mannose D-Rhamnose L-Rhamnose Alpha-L-Rhamnopyranose

Methylpentoses give yellow stain with filter paper soaked with aniline acetate, while pentoses give red color. C) 2, 6-Deoxy-hexoses i) D-Digitoxose A component of the sugar part of Digitalis glycosides (Purpurea A, B and Lanatoside A and B) in D. purpurea and D. Lanata leaves, respectively.

CHO CHO 6 CH3 H OH H H O H OH H OH

H OH H OH OH 2 OH H OH H OH OH

CH OH CH 2 3 D-Digitoxose D-Allose ii) D-Cymarose

A component of the sugar part of K- strophanthoside, K-strophanthin and Cymarin glycosides in Strophanthus kombe

CHO 6 H H CH3 O H OCH3 H OH OH 2 OH H OH OCH3 CH3 D-Cymarose Alpha-D-Cymarose Keller Killiani test (for 2,6-Deoxy sugar) 70% alcoholic digitalis extract, heat & filter.

- Add 5 mL lead acetate solution.

- Shake & filter - Shake the filtrate with chloroform, - Separate the chloroform layer - Evaporate the chloroform layer to dryness

Residue

- 3 mL glacial acetic acid and 2 drops of FeCl3

- Add cautinously on the wall of test tube Conc. H2SO4 containg traces of FeCl3

Intense blue color develops at the surface between the two layers