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General characteristic of the carbohydrates, their sources of getting, properties, qualitative and quantitative analysis, storage and usage. Tannins.

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Lecture 13 General characteristic of the carbohydrates, their sources of getting, properties, qualitative and quantitative analysis, storage and usage. – PowerPoint PPT presentation

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Title: General characteristic of the carbohydrates, their sources of getting, properties, qualitative and quantitative analysis, storage and usage. Tannins.


1
  • Lecture ?13
  • General characteristic of the carbohydrates,
    their sources of getting, properties, qualitative
    and quantitative analysis, storage and usage.
    Tannins.
  • prepared assist. Logoyda L.S.

2
  • Carbohydrates  are carbon compounds that contain
    large quantities of hydroxyl groups . The
    presence of the hydroxyl groups allows
    carbohydrates to interact with the aqueous
    environment and to participate in hydrogen
    bonding. Carbohydrates can combine with lipid to
    form glycolipids or with protein to form
    glycoproteins.
  • They have a wide range of functions including
    providing a significant fraction of the energy
    in the diet of most organism , acting as a
    storage form of energy in the body and serving as
    cell membrane components.
  • Also carbohydrates serve as a structural
    component of many organisms including cell walls
    of bacteria.
  • Carbohydrates serve as metabolic intermediate (
    e.g Glucose 6 phosphate, fructose 1,6
    diphosphate).
  • Ribose ,deoxyribose play a major role in the
    synthesis DNA and RNA.
  • all life activities are dependent upon
    carbohydrates. When insufficient carbohydrates
    are available from the diet, the body converts
    fat reserves to carbohydrates for its use, and
    amino acids are utilized as carbohydrates instead
    of being used to make body protein.
    Carbohydrates, along with proteins and fats,
    comprise the major components of living matter
    and are used for maintenance of cellular
    functional activities and as reserve and
    structural materials for cells

3
  • Carbohydrates with an aldehyde group are called
    aldoses where those with a keto group are called
    ketoses. For example , glyceraldehyde is an
    aldose, whereas, dihydroxyacetone is a ketose.
  • Disaccharides contain two monosaccharides units.
    Maltose , sucrose
  • Oligosaccharides contain from three to about 12
    monosaccharides units. For example, Blood group
    antigens.
  • Polysaccharides contain more than 12
    monosaccharides units and can be hundreds of
    sugar units in length. Starch , cellulose
  • All carbohydrates can be hydrolyzed (broken
    down) into two or more monosaccharides.
  • For further understanding of these different
    classifications of carbohydrates, the
    monosaccharides and disaccharides can be grouped
    together and compared with the polysaccharides.
    This can be done because monosaccharides and
    disaccharides have certain things in common.
  • They are both water soluble. In addition, they
    have a sweet taste and a crystalline structure.

4
  • Simple sugars, starches and cellulose are
    organic compounds that have the approximate
    formula C(H2O)n, which accounts for the name
    carbohydrate (or hydrate of carbon) that is
    usually applied to this group of compounds They
    are not truly hydrates of carbon but are
    polyhydroxy (alcohol) compounds that contai an
    aldehyde or ketone functional group. These
    functional groups give the carbohydrates some of
    their chemical properties that will be studied in
    this lab.

5
  • Monosaccharides
  • Simple sugars cannot be hydrolysed further.
    They are further classified on the basis of
    number of carbon atoms present as well as on the
    presence of functional groups.

6
Carbon atoms Examples Functional groups
Trioses (3 carbon) Glyceraldehyde Dihydroxy acetone Aldehyde (aldotriose) Ketone (Ketotriose)
Tetroses (4 carbon) Erythrose Aldehyde (aldotetrose)
Pentoses (5 carbon Ribose Xylose Xylulose Aldehyde(Aldopentose) Aldehyde(Aldopentose) Ketone (Ketopentose)
Hexoses (6 carbons) Glucose Galactose Fructose Aldehyde (Aldohexose) Aldehyde (Aldohexose) Ketone (Ketohexose)
7
Disaccharides.
  • Contain two molecules of same or different
    monosaccharide units. On hydrolysis they give two
    monosaccharide units. Monosaccharide units are
    joined by glycosidic bond.

8
Examples Product formed Upon hydrolysis Glycosidic Linkage Sources
Maltose glucose glucose a 1-4 Malt
Lactose galactose glucose ß 1-4 Milk
Sucrose glucose Fructose ß 1-2 Sugar cane
Isomaltose glucose glucose a 1-6 Digestion of amylopectin
9
Oligosaccharides
  • Contain - molecules of monosaccharide units.
  • E.g. Maltotriose. (Glucose Glucose Glucose)

10
The D Aldose Family
11
Carbohydrates
12
Isomers and epimers
  • Compounds that have the same chemical formula but
    have different structures are called isomers. For
    example Fructose, glucose , mannose and galactose
    are all isomers of each other having the same
    chemical formula C6H12O6. If two monosaccharides
    differ in configuration around only one specific
    carbon atom , they are defined as epimers of each
    other. For example, glucose and galactose are C4
    epimers, their structures differ only in the
    position of the hydroxyl group at C4 ( Note , the
    carbons in sugar are numbered beginning at the
    end that contain the aldehyde or ketone group.
  • Glucose and mannose are C2 epimers. However,
    galactose and mannose are not epimers they differ
    in the position of the hydroxyl group at two
    carbon 2 and 4 and therefore, defined only as
    isomers.
  • Enantiomers A special type of isomerism is found
    in the pairs of structures that are mirror images
    of each other. These mirror images are called
    enantiomers. The two members of the pair are
    called as D and L sugars. The majority of the
    sugars in human are D sugars.

13
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14
Anomeric carbon
  • Formation of a ring results in the creation of an
    anomeric carbon at C1 of an aldose or C2 of a
    ketose. These structures are called the a andß
    configuration of the sugar . For example a-D
    glucose and ß-D-glucose. These two sugars are
    both glucose but they are anomers of each other.
    Enzymes are able to distinguish between these two
    structures and use one or the other
    preferentially. For example glycogen is
    synthesised from a-D glucosepyranose whereas,
    cellulose is synthesised from ß-D-glucopyranose.
    The cyclic a and ß anomers of a sugar in solution
    are in equilibrium with each other and can be
    spontaneously interconverted in a process called
    mutarotation.

15
Optical activity
  • The compounds having asymmetric carbon atoms
    can rotate the beam of plane polarized light and
    are said to be optically active. An isomer which
    can rotate the plane of polarized light to the
    right is called as dextrorotatory and is
    designated as (d) or () Example D- (d)-glucose
    or it is also known as dextrose. While the isomer
    which rotates the plane of polarized light to
    left is known as levorotatory, and is identified
    as (l) or (-). Example D-(l)-fructose.

16
  • A levorotatory () substance rotates polarized
    light to the left. E.g., l-glucose (-)-glucose
    A dextrorotatory () substanc rotates polarized
    light to the right. E.g., d-glucose
    ()-glucose
  • Molecules which rotate the plane of of
    polarized light are optically active. Most
    biologically important molecules are chiral, and
    hence are optically active. Often, living systems
    contain only one of all of the possible
    stereochemical forms of a compound. In some
    cases, one form of a molecule is beneficial, and
    the enantiomer is a poison (e.g., thalidomide).

17
Polarimetry
monochromator
polarizer
sample cell
light source
18
Glucose cyclic formed by reaction of CHO with -OH
on C5.
19
Glucose
  • Ribose and deoxyribose

20
Anomers
21
Mutarotation
22
Reducing Sugars
  • If the oxygen on the anomeric carbon of a sugar
    is not attached to any other structure that sugar
    is a reducing sugar .A reducing sugar can react
    with chemical reagents ( Benedicts solution ) and
    reducing the reactive component with the anomeric
    carbon becoming oxidized ( Note only oxygen on
    the anomeric carbon determines if the sugar is
    reducing or non-reducing .

23
  • Glucose
  • This monosaccharide is the most important
    carbohydrate in human nutrition because it is the
    one that the body fuses directly to supply its
    energy needs. Glucose is formed from the
    hydrolysis of di- and polysaccharides, including
    starch, dextrin, maltose, sucrose and lactose
    from the monosaccharide fructose largely during
    absorption and from both fructose and galactose
    in the liver during metabolism.
  • Glucose is the carbohydrate found in the
    bloodstream, and it provides an immediate source
    of energy for the body's cells and tissues.
    Glucose is also formed when stored body
    carbohydrate (glycogen) is broken down for use.
  • Fructose
  • Fructose, a monosaccharide, is very similar to
    another monosaccharide, galactose. These two
    simple sugars share the same chemical formula
    however, the arrangements of their chemical
    groups along the chemical chain differ. Fructose
    is the sweetest of all the sugars and is found in
    fruits, vegetables and the nectar of flowers, as
    well as molasses and honey. In humans, fructose
    is produced during the hydrolysis of the
    disaccharide, sucrose.

24
  • Galactose
  • Galactose differs from the other simple sugars,
    glucose and fructose, in that it does not occur
    free in nature. It is produced in the body in the
    digestion of lactose, a disaccharide.

25
Disaccharides 
  • . The linkage of two monosaccharides to form
    disaccharides involves a glycosidic bond by
    dehydration . Several physiogically important
    disaccharides are sucrose, lactose and maltose.
  • Sucrose
  • prevalent in sugar cane and sugar beets, is
    composed of glucose and fructose through an
    a-(1,2)ß -glycosidic bond.
  • Lactose 
  • is found exclusively in the milk of mammals and
    consists of galactose and glucose in a ß -(1,4)
    glycosidic bond.
  • This disaccharide is found only in milk. Human
    milk contains about 4.8 g per 100 ml and cow's
    milk contains approximately 6.8 g per 100 ml.
    When lactose is hydrolyzed it yields one unit of
    the monosaccharide glucose and one unit of the
    monosaccharide galactose. The enzyme lactase is
    needed to digest lactose.
  • Maltose This involved C1 and C4 , this
    special bond is called 1-4 glycosidic bond.
    Maltose occurs in the body as an intermediate
    product of starch digestion. (Starch is a
    polysaccharide.) When maltose is hydrolyzed, it
    yields two molecules of glucose.

26
Sucrose
27
Lactose
28
Maltose
29
Polysaccharides
  • Most of the carbohydrates found in nature occur
    in the form of high molecular weight polymers
    called polysaccharides . The building blocks used
    to generate polysaccharides can be varied
    however, the predominant monosaccharide found in
    polysaccharides is D-glucose. When
    polysaccharides are composed of a single
    monosaccharide building block, they are termed
    homopolysaccharides. Polysaccharides composed of
    more than one type of monosaccharide are termed
    heteropolysaccharides. Many polysaccharides
    unlike sugars are insoluble in water. Dietary
    fiber include polysacchaides and oligosaccharides
    that are resistant to digestion and absorption in
    the human small intestine but which are
    completely or partially fermented by
    microorganisms in the large intestine.
  •  

30
  • Glycogen
  • Glycogen is the major form of stored carbohydrate
    in animals. This molecule is a homopolymer of
    glucose in a-(1,4) linkage it is also highly
    branched, with a-(1,6) branch linkages occurring
    every 8-10 residues. Glycogen is a very compact.
    This compactness allows large amounts of carbon
    energy to be stored in a small volume. Glycogen
    is the reserve carbohydrate in humans. Glycogen
    is very similar to amylopectin, having a high
    molecular weight and branched-chain structures
    made up of thousands of glucose molecules. The
    main difference between glycogen and amylopectin
    is that glycogen has more and shorter branches,
    resulting in a more compact shape.
  • Glycogen is stored primarily in the liver and
    muscles of animals. About two-thirds of total
    body glycogen is stored in the muscles and about
    one-third is stored in the liver.
  • Starch is the major form of stored carbohydrate
    in plant cells. Its structure is identical to
    glycogen, except for a much lower degree of
    branching (about every 20-30 residues).
    Unbranched starch is called amylose branched
    starch is called amylopectin

31
  • Amylose Molecules consist of 200- 20,000
    glucose units which form helix as a result of the
    bond angles between the glucose units.( a- 1,4
    glycosidic linkage).
  • Amylopectin Differs from amylose is being
    highly branched. Short side chains of about 30
    glucose units are attached with a 1-6 linkage
    approximately every 20- 30 glucose unit along
    the chain . Amylopectin molecules may contain up
    to 2 million glucose units.
  • Dextran Is a polysaccharides similar to
    amylopectin but the main chains are formed by
    a1-6 glucosidic linkages and the side branches
    are attached by a1-3 or a 1-4 linkages. Dextran
    is an oral bacterial product that adheres to the
    teeth , creating a film called plague. It is used
    commercially as food additives .
  • Cellulose Is composed of chains of D-glucose
    unit joined by ß 1-4 glycosidic linkages. The
    chains are linear unbranched .It is a structural
    polysaccharides of plant cells. Like starch and
    glycogen, cellulose is composed of thousands of
    glucose molecules. It is the structural
    constituent of the cell walls of plants.
    Cellulose is, therefore, the most abundant
    naturally-occurring organic substance. It is
    characterized by its insolubility and its
    physical rigidity. This polysaccharide can be
    digested by cows, sheep, horses, etc., as these
    animals have bacteria in their rumens (stomachs)
    whose enzyme systems break down cellulose
    molecules. Humans do not have the enzyme needed
    to digest cellulose, so it is passed through the
    digestive tract unchanged.

32
Amylose
33
Amylopectin
34
Cellulose
35
  • Amino sugars Glucosamine, Galactosamine
  • Sugar acids Ascorbic acid, Glucuronic
    acid
  • Sugar alcohol D-Sorbitol from D-glucose
  • D- Mannitol from
    D- Mannose
  • D-Dulcitol from D-
    Galactose
  • Glycoprotein Component of cell wall and
    membrane
  • Blood group antigens Specific oligosaccharides
    bound to proteins , lipids on
    membrane surfaces.

36
  • Disease Conditions Related To Carbohydrate
    Consumption
  • 1. Lactose intolerance
  • 2. Galactosemia
  • 3. Dental caries
  • 4. Diabetes mellitus
  • 5. Hypoglycemia.

37
Functions of carbohydrates
  • 1. Most abundant dietary source of energy
    (4Cal/g)
  • 2. They are precursors for many organic compounds
    (fats, amino acids)
  • 3. Carbohydrates (glycoprotein, glycolipids)
    participate in the structure of cell membrane and
    cellular functions
  • 4. Structural components of many organisms. These
    include the fibers (cellulose) of plant,
    exoskeleton of some insects and the cell wall of
    microorganisms.
  • 5. Serve as the storage form of energy (glycogen)
    to meet the immediate energy demands of the body.

38
Qualitative Tests for Carbohydrates
  • Reducing sugars are usually detected with
    Benedict's reagent, which contains Cu2 ions
  • in alkaline solution with sodium citrate added
    to keep the cupric ions in solution. The alkaline
  • conditions of this test causes isomeric
    transformation of ketoses to aldoses, resulting
    in all monosaccharides and most disaccharides
    reducing the blue Cu2 ion to cuprous oxide
    (Cu2O), a brick red-orange precipitate. This
    solution has been used in clinical laboratories
    for testing urine.

39
  • Barfoed's solution contains cupric ions in an
    acidic medium. The milder condition allows
    oxidation of monosaccharides but does not oxidize
    disaccharides. If the time of heating is
    carefully controlled, disaccharides do not react
    while reducing monosaccharides give the positive
    result (red Cu2O precipitate). Ketoses do not
    isomerize with this reagent. Carbohydrates are
    dehydrated in the presence of nonoxidizing acids
    to form furfural and hydroxymethylfurfural.

40
  • Seliwanoff's reagent contains resorcinol in 6 M
    hydrochloric acid. Hexoses undergo dehydration
    when heated in this reagent to form
    hydroxymethylfurfural, that condenses with
    resorcinol to give a red product. Ketohexoses
    (such as fructose) and disaccharides containing a
    ketohexose (such as sucrose) form a cherry-red
    condensation product. Other sugars may produce
    yellow to faint pink colors.

41
  • Bial's reagent contains orcinol
    (5-methylresorcinol) in concentrated HCl with a
    small amount of FeCl3 catalyst. Pentoses are
    converted to furfural by this reagent, which form
    a bluegreen color with orcinol. This test is used
    to distinguish pentoses from hexoses.

42
  • Iodine forms a deep blue color in the presence
    of starch. Potassium iodide is added to the
    reagent solution in order to make the iodine more
    soluble in water. Some forms of starch may yield
    a greenish color. Simple carbohydrates (mono- and
    disaccharides) and cellulose do not cause any
    change in the orange-brown color of the iodine
    reagent.

43
Glucose anhydrous
Appearance. The crystalline powder of white color
with sweet taste. Solubility. Easily soluble in
water R, moderately soluble in 96 alcohol R.
44
IDENTIFICATION
  1. TLC
  2. Reaction with reagents Feling. 0.1 g of the
    substance is dissolved in 10 ml of water R, 3 ml
    solution of copper tartratic R is added and it is
    heated red sediment is formed

45
  • 3. To the 0,02 g of the substance are added a few
    crystals of resorcinol R, 1-2 ml of dilute
    hydrochloric acid R and it is heated till
    boiling there appears pink color.
  • 4. To 0,01 g of the substance is added 0.01 g
    thymol R, 5-6 drops of sulphate acid R and R 1-2
    drops of water R there appears dark red color.

46
TEST ON PURITY
  • Irrelevant sugars, soluble starch, dextrins. 1.0
    g of the substance is dissolved by boiling in 30
    ml of alcohol (90 v / v) R then it is cooled
    the solution must remain transparent.

47
QUANTITATIVE DETERMINATION
  • State Pharmacopoeia of Ukraine does not provide
    quantitative determination of glucose in the
    substance.
  • Iodometry, the reverse titration
  • Approximately 0.1 g of substance (exact batch),
    is placed in a flask capacity 250 ml, it is
    dissolved in 10 ml of water R. It is added 20.0
    ml of 0.05 M solution of iodine, 10.0 ml of 1
    solution of sodium hydroxide R and left for 15
    min. Then the solution is acidified by 10 ml
    dilute acid sulphate R and titrated by 0.1 M
    solution of sodium thiosulfate (indicator -
    starch solution R). In parallels a control
    experiment is conducted.

48
  • I2 2NaOH ? NaI NaIO H2O
  • NaIO NaI H2SO4 ? I2 Na2SO4 H2O
  • I2 2Na2S2O3 ? 2NaI Na2S4O6.
  • Em ?. ?./2

49
  • STORAGE
  • In tightly closed container.
  • APPLICATION
  • During various diseases of heart, liver, at
    shock treatment, collapse, as a source of
    nutrition, which is easily assimilated by
    organism and improves the functions of different
    organs.

50
  • Tannins can be modified to change their
    solubility properties or to eliminate the
    reactive phenolic functional groups. The modified
    tannins do not retain the characteristic chemical
    or biological reactivities of native tannins.

51
Acetylation
  • Puts an acetyl group on each hydroxyl group of
    the starting material. Polarity of the tannin is
    diminished, and it is insoluble in aqueous
    solvents. Slowly drip a mixture of 5 mL pyridine
    and 5 mL fresh acetic anhydride into a flask
    containing 2 g tannic acid. Pour the solution
    into water a solid should form. The solid is
    washed with dilute acetic acid (to remove the
    pyridine) and then with water. It can be freeze
    dried. Its IR spectrum shows loss of the phenolic
    OH group.

52
Methylation
  • Converts each hydroxyl group to its methyl
    ester. Polarity of the tannin is diminished and
    its solubility altered. We have not attempted
    this procedure. To methylate tannin, mix it with
    excess methyl iodide, reagent acetone and solid
    potassium carbonate. Reflux the mixture overnight
    and purify the product.
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