Lecture № 15
THEME: Di- and polysaccharides.
Terpenes.
associate. prof. Ye. B. Dmukhalska, assistant. I.I. Medvid
Outline
1.Oligosaccharides.
2. The following functions of carbohydrates in humans.
Classification of disaccharides.
3. Polysaccharides (glucanes).
a) Homopolysaccharides:
b) Heteropolysaccharides.
4. Glycoconjugates.
5. Lipids: Fats. Phospholipids. Waxes. Nonsaponifiable lipids.
6. Terpenes and terpenoids. Terpene biosynthesis. Classification of
terpenes.
7. Carotenoids. Steroids. Properties of cholesterol. Biosynthesis of
cholesterol.
8. Vitamins. Water-soluble vitamins. Water insoluble (lipid-soluble)
vitamins.
Disaccharides. А monosaccharide that has cyclic forms
(hemiacetal or hemiketal) can react with an alcoho1 to form а
glycoside (acetal or ketal). This same type of reaction can be used
to produce а disaccharide, а carbohydrate in which two
monosaccharides are bonded together. In disaccharide formation,
one of the monosaccharide reactants functions as а hemiacetal or
hemiketal, and the other functions as an alcohol.
Monosaccharide + monosaccharide = disaccharide + Н2O
The bond that links the two monosaccharides of а disaccharide together is called а glycosidic
linkage. А glycosidic linkage is the carbon-oxygen-carbon bond that joins the two components of
а glycoside together. The bond that links the two monosaccharides of а disaccharide together is
called а glycosidic linkage. We now examine the structures and properties of four important
disaccharides: maltose, cellobiose, lactose, and saccharose. As we consider details of the
structures of these compounds, we will find that the configuration (α or β) at carbon-1 of the
reacting monosaccharides is often of prime importance.
Maltose, often called malt sugar, is produced by breaking
down the polysaccharide starch, as takes place in plants when
seeds germinate and in human beings during starch digestion.
It is а common ingredient in baby foods and is found in malted
milk. Malt (germinated barley that has been baked and ground)
contains maltose; hence the name malt sugar. Structurally,
maltose is made up of two D-glucopyranose units, one of
which must be -D-glucose. The formation of maltose from
two glucose molecules is as follows:
-D-Glucose
-D-Glucose
-(1-4)-linkage
So, α-maltose can be named as 4-O-(α-Dglucopyranosido)-α-D-glucopyranose, β-maltose – 4O-(α-D-glucopyranosido)-β-D-glucopyranose.
The glycosidic linkage between the two glucose units is called
an (1 - 4) linkage. The two ОН-groups that form the linkage
are attached, respectively, to carbon-1 of the first glucose unit
(in an a configuration) and to carbon-4 of the second. Maltose
is а reducing sugar, because the glucose unit on the right has а
hemiacetal carbon atom (С-1).Thus this glucose unit can open
and close; it is in equilibrium with its open-chain aldehyde
form. This means there are actually three forms of the maltose
molecule: -maltose, -maltose, and the open-chain form. In
the solid state, the -form is dominant. The most important
chemical reaction of maltose is hydrolysis. Hydrolysis of Dmaltose, whether in а laboratory flask or in а living organism,
produces two molecules of D-glucose.
CH
2
O
H
CH
OH
OH
H
H
O
H
OH
OH
H
[O]
2
CH
OH
O
H
OH
OH
H
2
OH
OH
H
H
H
H
O
O
H
OH
H
HO
HO
H
CH
OH
O
H
H
2
OH
C
OH
H
OH
maltoboinic acid
H
OH
CH 2 OH
CH 2 OH
H
HO
O
H
H
OH
H
O
O
CH3OH (HCl,gas)
H
H
OH
OH H
HO
H
OH
H
CH 2 OH
CH 2 OH
OH
O
H
H
OH
H
H
O
OH
O
H
OH H
H
OCH 3
OH
methylmaltozide
CH2OCH3
O
OH
H
H H
H
OCH3
H
H
O OCH3
OCH3
CH3O
OCH3
H OCH3
H
CH2OCH3
CH3J або (CH3)2SO4
CH2OH
O
OH
H
H H
H
OH H O OH H
HO
CH2OH
H
OH
H
OH
(CH3CO)2O
(Ac = CH3CO)
HOH, H+
OH
CH2OAc
O
OH
H
H H
H
OAc H O OAc H
AcO
OAc
H OAc
H
CH2OAc
OAc
HOH, H+
CH2OCH3
O
H H
CH2OCH3
HOH, H+
H
CH3O
H
OCH H
3
H
HOH, H+
O H
O
OCH3
OH
OCH3
H
CH2OAc
+
CH3OH
OCH3
CH2OAc
O
O H
H
H H
H
OAc H
OAc H
O
AcO
OAc
OAc
H
H
OH
+
CH3COOH
Cellobiose is produced as an intermediate in the
hydrolysis of the polysaccharide cellulose. Like maltose,
cellobiose contains two D-glucose monosaccharide units. It
differs from maltose in one of D-glucose units - the one
functioning as а hemiacetal - must have а -configuration
instead of the а configuration of maltose. This change in
configuration gives а (1-4) glycosidic linkage.
-D-Glucose
(1-4)-linkage
α-cellobiose can be named as 4-O-(β-Dglucopyranosido)-α-D-glucopyranose, β-cellobiose – 4O-(β-D-glucopyranosido)-β-D-glucopyranose.
Like maltose, cellobiose is a reducing sugar, has three
isomeric forms in aqueous solution, and upon hydrolysis
produces two D-glucose molecules. Despite these similarities,
maltose and cellobiose have different biological behaviors.
These differences are related to the stereochemistry of their
glycosidic linkages. Maltase, the enzyme that breaks the
glucose-glucose (1-4) linkage present in maltose, is found
both in the human body and in yeast. Consequently, maltose is
digested easily by humans and is readily fermented by yeast.
Both the human body and yeast lack the enzyme cellobiase
needed to break the glucose - glucose (1-4) linkage of
cellobiose. Thus cellobiose cannot be digested by humans or
fermented by yeast. In maltose and cellobiose, the two units of
the disaccharide are identical - two glucose units in each case.
Maltose and cellobiose have different arrangement in space. In
maltose molecule α-glycosidic linkage has axial arrangement,
in cellobiose molecule β-glycosidic linkage – equatorial. Its
cases club-similar structure of amylose and linear structure of
cellulose.
Lactose includes -D-galactopyranose unit and а Dglucopyranose unit joined by -(1-4) glycosidic linkage
-D-galactose
-D-Glucose
(1-4)-linkage
The glucose hemiacetal center is active when galactose bonds to glucose in the
formation of lactose, so lactose is а reducing sugar (the glucose ring can open to give
an aldehyde).Lactose is the major sugar found in milk. This accounts for its common
name, milk sugar. Enzymes in animal mammary glands take glucose from the
bloodstream and synthesize lactose in а four-step process. Epimerization of glucose
yields galactose, and then the (1-4) linkage forms between а galactose and а glucose
unit. Lactose is an important ingredient in commercially produced infant formulas that
are designed to simulate mother' s milk. Souring of milk is caused by the conversion of
lactose to lactic acid by bacteria in the milk. Pasteurization of milk is а quick-heating
process that kills most of the bacteria and retards the souring process. Lactose can be
hydrolyzed by acid or by the enzyme lactase, forming an equimolar mixture of
galactose and glucose. In the human body, the galactose produced in such way is then
converted to glucose by other enzymes. The genetic condition lactose intolerance, an
inability of the human digestive system to hydrolyze lactose.
α-lactose can be named as 4-O-(β-D-galactopyranosido)-α-D-glucopyranose,
β-lactose – 4-O-(β-D-galactopyranosido)-β-D-glucopyranose.
Arrangement in space is similar to cellobiose:
Sucrose can be named as 2-O-(α-D-glucopyranosido)-β-Dfructofuranose.
Sucrose, unlike maltose, cellobiose, and lactose, is а
non-reducing sugar. No helmiacetal or hemiketal center
is present in the molecule, because the glycosidic linkage
involves the reducing ends of both monosaccharides.
Sucrose, in the solid state and in solution, exists in only
one form - there are no  and  isomers, and an openchain form is not possible. Sucrose, the enzyme needed
to break the ,(1 - 2) linkage in sucrose, is present in
the human body. Hence sucrose is an easily digested
substance.
dextrorotatory
laevorotatory
Linear and branched structure of
polysaccharides
Homopolysaccharides
Structure, composition and properties of
cellulose.
Cellulose is the most abundant polysaccharide. It
is the structural component of the cell walls of plants.
Approximately half of all the carbon atoms in the
plant kingdom are contained in cellulose molecules.
Structurally, cellulose is а linear (unbranched) Dglucose polymer in which the glucose units are linked
by (1-4) glycosidic bonds.
• At heating with mineral acids cellulose
hydrolyzed by the following scheme:
In cellulose glucopyranose remainders
have linear structure and hydrogen bonds:
High-fiber food may also play а role in weight control.
Obesity is not seen in parts of the world where people eat large
amounts of fiber-rich foods. Many of the weight-loss products
on the market are composed of bulk-inducing fibers such as
methylcellulose.
•
FIGURE. Cellulose microfibrils.
Some fibers bind lipids such as cholesterol and
carry out them of the body with the feces. This
lowers blood lipid concentrations and possibly the
risk of heart and artery disease.
In amylose's structure, the glucose units are connected by
(1- 4) glycosidic linkages.
Starch (amylose)
The number of glucose units present in an amylose chain
depends on the source of the starch; 200 – 350 monomer units
are usually present. Amylopectin, the other polysaccharide in
starch, is similar to amylose, but has а high degree branched
structure in the polymer. А one branch link containe 20-25
glucose units. The number of glucose units present in an
amylopectin chain consists of 1000 and more units. The branch
points involve (1 – 6) linkages:
Starch (amylopectin)
•
•
•
Glycogen is an ideal storage form for glucose. The large
size of these macromolecules prevents them from diffusing out
of cells. Also, conversion of glucose to glycogen reduces
osmotic pressure. Cells would burst because of increased
osmotic pressure if all of the glucose in glycogen were present
in cells in free form. High concentrations of glycogen in а cell
sometimes cases precipitate or crystallize into glycogen
granules. These granules are discernible in photographs of
cells under electron microscope magnification. The glucose
polymers amylose, amylopectin, and glycogen compare as
follows in molecular size and degree of branching:
Amylose: Up to 1000 glucose units; no branching
Amylopectin: Up to 100,000 glucose units; branch points
every 20-25 glucose units
Glycogen: Up to 1,000,000 glucose units; branch points every
8-12 glucose units
Because of the branching, amylopectin has а
larger average molecular mass than the linear
amylose. The average molecular mass of amylose is
40000 or more; it is 1-6 mln. for amylopectin. Note
that all of the glycosidic linkages in starch (both
amylose and amylopectin) are of the -type. In
amylose, they are all (1 - 4); in amylopectin, both
(1 -4) and (1 -6) linkages are present. Because а
linkages can be broken through hydrolysis within the
human digestive tract (with the help of the enzyme
amylase), starch has nutritional value for humans.
The starches present in potatoes and cereal grains
(wheat, rice, corn, etc.) account for approximately
two-thirds of the world' s food consumption.
Fermentayion hydrolysis of starch is shown below:
FIGURE. Structure of amylopectine (а), glycogen (b)
Dextranes
• Dextranes have bacterial origin, contain remainders of α-D-
glucopyranose. Dextranes obtain from sucrose at the present of
bacterium (Leuconostoc mesenteroides). The main type of bond is
α-1,6-glycosidic bond, in place of branching – α-1,4- and α-1,3glycosidic bonds. The average molecular mass of dextranes is few
millions. Partly hydrolyzed dextranes (m. m. – 40000-800000) use in
pharmacy as plasmasubstitute (“Polyglucin”, “Reopolyglucin”).
Inuline
• Inuline – reserve polysaccharide, present in
plants. Inuline has linear structure and
consists of remainders of β-Dfructofuranose, joined by 2,1-glycosidic
bonds, in the end of inuline is α-Dglucopyranose remainder (like sucrose).
Molecular mass of inuline is up to 6000. Use
for obtaining of D-fructose.
Pectin compounds
• Pectin compounds (pectins) –
polysaccharides consist of polygalacturonic
acid, which contain remainders of α-Dgalacturonic acid joined by 1,4glycosidic bonds. Part of carboxyl grups
present in appearance of methyl ether.
Water solutions of pectins form stable
gels. Pectins have antiulcer properties.
It is а highly viscous substance and has а molecular weight in
several hundred millions. Hyaluronic acid is а principal component
of the ground substance of connective tissue. Among other places it
is found in skin, synovial fluid, vitreous hemour of the eye, and
umbilical cord. It exercises а cementing function in the tissues and
capillary walls, and forms а coating gel round the ovum. It accounts
for about 80% of the viscosity of synovial fluid which contains
about 0. 02 – 0.05% of hyaluronate. Repeat part of hyaluronic acid
is D-glucuronic acid and N-acetyl-D-glucosamine joined by β1,3-glycosidic bond, between disaccharide fragments – β-1,4.
Molecular mass of hyaluronic acid is from 1600 to 6400.
(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy--D-glucopyranose.
Chondroitin sulfate. It has similar structure as hyaluronic acid
with the difference that the N-acetyl-D-glucosamine unit of the
molecule is replaced by N-acetyl-D-galactosamine unit with
sulphate group. Repeat part of chondroitin sulphate is D-glucuronic
acid and N-acetyl-D-galactosamine which contains sulfate group.
Inside of disaccharide fragment is β-1,3-glycosidic bond; between
fragments – β-1,4. Sulfate group forms ether bond with hydroxyl
group of N-acetyl-D-galactosamine in location 4 (chondroitin-4sulfate) or in location 6 (chondroitin-6-sulfate). Chondroitin
sulfates are found in cartilage, bone, heart valves, tendons and
cornea.
(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo--Dgalactopyranose.
Hydrocarbon chains of chondroitin-4-sulfate contain
up to 150 disaccharides remainders, joined in
organism by O-glycosidic bonds with hydroxyl groups
of aminoacid remainders.
Dermatan sulfate. (Varying amounts of Dglucuronic acid may be present. Concentration
increases during aging process.)
(1,4)-O--L-idopyranosyluronic acid-(1,3)-2acetamino-2-dezoxy-4-O-sulfo--Dgalactopyranose.
Heparin. It is naturally occurring anticoagulant found mainly
in the liver, and also in lung, spleen, kidney and intestinal mucosa.
It prevents blood clotting by inhibiting the prothrombin-thrombin
conversion and thus eliminating the thrombin effect on fibrinogen.
Repeat part of heparin consists of D-glucosamin and uronic acid,
joined by α-1,4-glycosidic bonds. As uronic acid in heparin present
L-iduronic acid or, very rare, D-glucuronic acid. Remainders of
glucosamine and L-iduronic acid partly sulfonated. Molecular mass
of heparin is 16000-20000.
(1,4)-O--D-idupyranosyluronic acid-2-O-sulfo-(1,4)-2sulfamino-2-dezoxy-6-O-sulfo--D-glucopyranose
Fig. Proteoglycan structure
Mucin-type carbohydrate While all N-linked
oligosaccharides are bound to protein via GlcNAc-Asn, the
linking groups of O-glycosidic oligosaccharides are of several
types. The most common of these is GalNAc-Ser (or GalNAcThr). Considerable mucin-type carbohydrate unit is
disaccharide such as Gal-1,3-GalNAc, found in the antifreeze
glycoprotein of antarctic fish (Figure), to the complex
oligosaccharides of blood groups such as those of the ABO
system.
Fig. Antifreeze glycoprotein structure.
6. Lipids
Lipids differ from the other classes of naturally occurring
biomolecules (carbohydrates, proteins, and nucleic acids), they
are more soluble in non- or weakly polar solvents (diethyl
ether, hexane, dichloromethane) than in water. They include a
variety of structural types, a collection of which is introduced
in this chapter. In spite of the number of different structural
types, lipids share a common biosynthetic origin in that they
are ultimately derived from glucose. During one stage of
carbohydrate metabolism, called glycolysis, glucose is
converted to lactic acid. Pyruvic acid is an intermediate
product.
Classification of lipids
Lipids are organic compounds, found in living
organisms, that are soluble in nonpolar organic solvents.
Because compounds are classified as lipids on the basis of a
physical property— their solubility in an organic solvent—
rather than as a result of their structures, lipids have a
variety of structures and functions, as the following
examples illustrate:
Fats and oils are naturally occurring mixtures of triacylglycerols,
also called triglycerides.They differ in that fats are solids at room
temperature and oils are liquids. We generally ignore this distinction and
refer to both groups as fats. Triacylglycerols are built on a glycerol
framework.
Simple triacylglycerines include similar fatty acids
,
mixed – different. All three acyl groups in a triacylglycerol
may be the same, all three may be different, or one may be
different from the other two.
Nomenclature, methods of getting
of fats
For simple glycerides the name is made up of the name of the alcohol
(glycerol) or its radical (glyceryl) and the name of the acid; or the name
of the acid concerned is changed to suffix in. For mixed glycerides, the
position and names of the acid groups are specified by Greek letters α, β,
α’ or by the numerals 1, 2 and 3.
Methods of getting:
1. O-acylation of alcohols;
2. Allocation from plants: melting out, pressing or
extraction by organic solvents.
The most widespread fatty acids in
natural oils and fats:
Double bonds are rigid structures, unsaturared acid molecules that
contain them can occur in two isomeric forms: cis and trans. In cis-isomers,
for example, similar or identical groups are on the same side of double
bond (a). When such groups are on opposite sides of a double bond, the
molecule is said to be a trans-isomer (b):
The double bonds in unsaturated fatty acids generally have the cis
configuration. This configuration produces a bend in the molecules, which
prevents them from packing together as tightly as fully saturated fatty
acids. As a result, unsaturated fatty acids have fewer intermolecular
interactions and, therefore, lower melting points than saturated fatty acids
with comparable molecular weights . The melting points of the unsaturated
fatty acids decrease as the number of double bonds increases. For example,
an 18-carbon fatty acid melts at 69 °C if it is saturated, at 13 °C if it has one
double bond, at if it has two -5 °C o double bonds, and at -11 °C if it has
three double bonds.
Triacylglycerols that are solids or semisolids at room temperature
are called fats. Fats are usually obtained from animals and are composed
largely of triacylglycerols with either saturated fatty acids or fatty acids
with only one double bond. The saturated fatty acid tails pack closely
together, giving the triacylglycerols relatively high melting points, causing
them to be solids at room temperature. Liquid triacylglycerols are called
oils. Oils typically come from plant products such as corn, soybeans,
olives, and peanuts. They are composed primarily of triacylglycerols with
unsaturated fatty acids that cannot pack tightly together. Consequently,
they have relatively low melting points, causing them to be liquids at
room temperature.
Hydrolysis of а triacylglycerol
Hydrolysis of а triacylglycerol is the
reverse of the esterification reaction by
which it wet formed. Complete hydrolysis
of а triacylglycerol molecule always gives
one glycerol molecule and three fatty acid
molecules as products.
7. Chemical properties of fats
1). Hydrolysis of fats with alkali (e.g., sodium hydroxide) yields salts of the
fatty acids, and those of the alkali metals, such as sodium or potassium, are
useig as soaps. Another name of this reaction – “saponification”:
The solubility of lipids in nonpolar organic solvents results from their
significant hydrocarbon component. The hydrocarbon portion of the
compound is responsible for its “oiliness” or “fattiness.” The word lipid
comes from the Greek lipos, which means “fat.”
2). Oxidation of fates.
Oxidation cases rancidity of fates.
During oxidation form aldehydes with short carbon chain.
Oxidation at the soft conditions (water solution of
KMnO4) cases formation of glycols. At the rigid
conditions carbon skeleton destroys with formation of
remainders of carbonic acids with shorter carbon
chains.
Fats, which predominantly contain saturated fatty acids, by
oxidation form ketones.
3). Hydrogenation.
Some or all of the double bonds of
polyunsaturated oils can be reduced by catalytic hydrogenation. Margarine
and shortening are prepared by hydrogenating vegetable oils such as soybean
oil and sunflower oil until they have the desired consistency. This process is
called “hardening of oils.” The hydrogenation reaction must be carefully
controlled, however, because reducing all the carbon–carbon double bonds
would produce a hard fat with the consistency of beef tallow. Quantity of H2 in
grams, which are necessary for hydration of 10kg of fats (hydration
number) characterizes unsaturating of fat.
4). Addition of halogens.
Iodine number for plants fats – 100-200, for
animal fats – 25-86, for fish fats – 100-193.
As might be expected from the properties of the fatty acids, fats
have a predominance of saturated fatty acids, and oils are composed
largely of unsaturated acids. Thus, the melting points of triglycerides
reflect their composition, as shown by the following examples. Natural
mixed triglycerides have somewhat lower melting points, the melting
point of lard being near 30 º C, whereas olive oil melts near -6 º C.
Since fats are valued over oils by some Northern European and North
American populations, vegetable oils are extensively converted to solid
triglycerides (e.g. Crisco) by partial hydrogenation of their
unsaturated components. Some of the remaining double bonds are
isomerized (to trans) in this operation. These saturated and trans-fatty
acid glycerides in the diet have been linked to long-term health issues
such as atherosclerosis.
8. Phospholipids. Waxes.
Triacylglycerols arise, not by acylation of glycerol itself,
but by a sequence of steps in which the first stage is acyl
transfer to L-glycerol 3-phosphate (from reduction of
dihydroxyacetone 3-phosphate, formed as described in Section
25.21). The product of this stage is called a phosphatidic
acid.
Hydrolysis of the phosphate ester function of the
phosphatidic acid gives a diacylglycerol, which then reacts
with a third acyl coenzyme A molecule to produce a
triacylglycerol. Phosphatidic acids not only are intermediates in
the biosynthesis of triacylglycerols but also are biosynthetic
precursors of other members of a group of compounds called
phosphoglycerides or glycerol phosphatides. Phosphoruscontaining derivatives of lipids are known as phospholipids, and
phosphoglycerides are one type of phospholipid. One important
phospholipid is phosphatidylcholine, also called lecithin.
Phosphatidylcholine is a mixture of diesters of phosphoric acid.
Classification of phospholipids
Washing action of soaps
Waxes
Waxes are water-repelling solids that are part of the
protective coatings of a number of living things, including the
leaves of plants, the fur of animals, and the feathers of birds.
They are usually mixtures of esters in which both the alkyl and
acyl group are unbranched and contain a dozen or more carbon
atoms. Beeswax, for example, contains the ester triacontyl
hexadecanoate as one component of a complex mixture of
hydrocarbons, alcohols, and esters.
9. Nonsaponifiable lipids
1). Prostaglandins – physiologically active
substances with biogenic origin, stimulate
smooth muscles and lowers blood
pressure. All prostaglandins contain
carboxyl group and 20 carbon atoms in
molecule, they are derivatives of
eyicosanic acid.
All the prostaglandins are 20-carbon carboxylic acids
and contain a cyclopentane ring. All have hydroxyl groups at C11 and C-15 (for the numbering of the positions in
prostaglandins). Prostaglandins belonging to the F series have
an additional hydroxyl group at C-9, and a carbonyl function is
present at this position in the various PGEs. The subscript
numerals in their abbreviated names indicate the number of
double bonds. Prostaglandins are believed to arise from
unsaturated C20-carboxylic acids such as arachidonic acid.
Mammals cannot biosynthesize arachidonic acid directly.
Prostaglandins have cyclopentane ring. According to allocation of double
bonds in fivemember cycle and side chains prostaglandins marked by
litters A, B, C, D, E and F.
According to the number of double bonds in side chains every group of
prostaglandins divided on series that marked as indexes.
In the names of prostaglandins orientation of hydroxyl
group in location 9 according to the carbon chain at
C8 mark α or β. α – means cis-configuration, β –
trance.
2). Isoprenoides – products of isoprene
transformation. Some vitamins and hormones have
isoprenoides structure.
Isoprenoides includes terpens, carotinoids and steroids
The following scheme shows how some of the many
monoterpenes could be synthesized from geranyl
pyrophosphate:
Classification of terpenes
Loss of a proton from the tertiary carbocation formed in this step gives
limonene, an abundant natural product found in many citrus fruits. Capture of
the carbocation by water gives -terpineol, also a known natural product.
Monoterpens
They are the terpenes that have been known for several
centuries as components of the fragrant oils obtained from
leaves, flowers and fruits. Monoterpenes, with sesquiterpenes,
are the main constituents of essential oils.
Acyclic monoterpens:
They can be considered as derivatives of 2,6-dimethyloctane.
In the basis of carbon skeleton acyclic monoterpens
are structures of isoprene isomeric dimers: myrcene
and ocimene.
Geraniol and nerol alcohols are derivatives of carbohydrates
monoterpens. Geraniol has cis-form and nerol – trance-form.
Among natural molecules, the followings are well
known and have several structural isomers.
Geraniol and citral present in ether oils, especially in citric oil. They are
pheromones.
Monocyclic monoterpenes
They are derived from cyclohexane with an isopropyl substituent. The
most important members are limonene and methane.
Limonene (dipentene) can be obtained by isoprene isomerisation with
heating to 150 C in soldered ampoule. At 500-700 C reverse processes
takes place.
– Catalytically hydrogenisation of limonene
– hydratation of limonene:
Menthane (1-isopropilmethylbenzol) is obtained from p-cimol (nisopropilmethylbenzol) hydration.
From hydroxyderivatives of menthane most important is menthol
(menthanol-3), which has tree asymmetric centers. (-)Menthol
synthesized by reducing of menthone.
Menthol has antiseptic,
sedative, analgesic
properties (Boromenthol,
Pectussine)
(+)Menthol in industry synthesized by alkylation of m-crezol with following hydration
of tymol.
Terpinehydrate (monohydrate menthandiol-1,8)
use in medicine in treatment of chronic
bronchitis.
Bicyclic monoterpenes:
The same tertiary carbocation serves as the precursor to
numerous bicyclic monoterpenes. A carbocation having a bicyclic
skeleton is formed by intramolecular attack of the electrons of the
double bond on the positively charged carbon. In the basis of
bicyclic monoterpenes are four cyclic terpenic carbohydrates:
α-Pinene contains in turpentine oil – turpentine
(up to 75 %).
Heating with dilute acids (H2SO4, HNO3):
After oxidation on air forms verbenon:
Borneol – alcohol of bornane (camphane) chain:
Isoborneol is borneol’s diastereomer:
Synthesis of difficult esters of borneol
Oxidation by chromic acid:
Interaction between borneol and acids:
Camphene can hydrolyze in acidic medium with
formation of isoborneol.
Camphor – bicyclic ketone, has two asymmetric atoms,
but dosen’t have diastereomers.
Camphor uses for stimulation of
respiratory and vesselmoving
centers, has antiseptic properties,
stimulates metabolite processes.
Tishchenko synthesis
Methylene group in α-location (according to carbonyl group) has CHacidic properties.
Oxidation of camphor with nitrate acid
Carotene – yellow-red pigment, contains in
carrot, milk and butter. Carotene is a mixture
of tree isomers – α-, β- and γ-carotene.
Carotenoids absorb visible light and dissipate its energy as
heat, thereby protecting the organism from any potentially harmful
effects associated with sunlight-induced photochemistry. They are
also indirectly involved in the chemistry of vision, owing to the fact
that -carotene is the biosynthetic precursor of vitamin A, also known
as retinol, a key substance in the visual process.
Steroids contain sterines, bile acids, steroid hormones,
aglycones of heart glycosides, aglycones of steroid
saponines.
Sterines (sterols) – steroid alcohols, which contain in
basis structure cholestane. Sterines are 3hydroxyderivatives of cholestane, may have one or few
double bonds. Divided on animal sterines (zoosterines),
plant sterines (phytosterines) and sterines of mushrooms
(mycosterines).
The most abundant member of the steroid family in animals is cholesterol
(cholesterine, cholestene-5-ol-3β) , the precursor of all other steroids.
Cholesterol is biosynthesized from squalene, a triterpene. Cholesterol is an
important component of cell membranes .Its ring structure makes it more rigid
than other membrane lipids. Because cholesterol has eight asymmetric carbons,
256 stereoisomers are possible, but only one exists in nature.
The steroid hormones can be divided into five classes: glucocorticoids,
mineralocorticoids, androgens, estrogens, and progestins. Glucocorticoids and
mineralocorticoids are synthesized in the adrenal cortex and are collectively
known as adrenal cortical steroids. All adrenal cortical steroids have an
oxygen at C-11.
• In lipids of human skin cholesteol transforms in vitamin D3
(cholecalciferrol) at the presents of UF-light.
Ergosterine (ergosterol, 24-methylcholestanetrien-5,7,22-ol-3β) refers
to mycosterine group. At the presents of UF-light ergosterol isomerizes in
vitamin D2 (ergocalciferrol)
Bile acids
Bile acids produce by liver from cholesterine and are
hydroxyderivatives of cholanic acid.
In human bile present 4 bile
acids, more popular are cholic
and dezoxycholic acids.
•
In addition to being the precursor of all the steroid
hormones in animals, cholesterol is the precursor of the bile
acids. In fact, the word cholesterol is derived from the Greek
words chole meaning “bile” and stereos meaning “solid.” The
bile acids—cholic acid and dezoxycholic acid—are
synthesized in the liver, stored in the gallbladder,and secreted
into the small intestine, where they act as emulsifying agents
so that fats and oils can be digested by water-soluble digestive
enzymes. Cholesterol is also the precursor of vitamin D.
Bile acids exist in organism in connection with glycine
aminoacid NH2CH2COOH or taurine NH2CH2CH2SO3H.
Steroid hormones
• Steroid hormones include corticosteroids and
sexual hormones. Corticosteroids produce in the
bark of adrenal glands, they are derivatives of
pregnane and divided into glucocorticoids and
mineralocorticoids.
Glucocorticoids, as their name suggests, are
involved in glucose metabolism, as well as in the
metabolism of proteins and fatty acids. Cortisone is
an example of a glucocorticoid. Because of its antiinflammatory effect, it is used clinically to treat
arthritis and other inflammatory conditions. Most
important glucocorticoids are hydrocortisone and
cortisone:
• Mineralocorticoids cause increased
reabsorption of HCO3
• control the balance of Na+, К+, Cl- ions in
cells and balance of water in the kidneys, take
part in regulation of blood pressure.
Aldosterone is an example of a
mineralocorticoid.
• Most important mineralcorticoids are
aldosterone and dezoxycorticosterone:
• In medicine also use synthetic analogs of
hydrocortisone and cortisone –
prednisolone, prednisone,
dexamethasone, triamcinolone. These
substances are more active then natural
corticosteroids.
The sexual hormones can be classified into three major groups:
• 1. Estrogens — the female sexual hormones
• 2. Androgens — the male sexual hormones
• 3. Progestins (gestagenes) — the pregnancy hormones
• The male sexual hormones, known as androgens are secreted
by the testes, estrogens – female sexual hormones are secreted
by the follicles in ovaries, pregnancy hormones form in yellow
body of ovaries.
They are responsible for the development of male secondary
sexual characteristics during puberty. They also promote
muscle growth. Testosterone and androsterone are androgens.
Synthetic steroid with androgen properties – methyltestosterone.
Estradiol and estrone (folliculine) are female sexual hormones known as
estrogens. They are secreted by the ovaries and are responsible for the
development of female secondary sex characteristics. They also regulate the
menstrual cycle. Progesterone is the hormone that prepares the lining of the
uterus for implantation of an ovum and is essential for the maintenance of
pregnancy. It also prevents ovulation during pregnancy.
Although the various steroid hormones have remarkably
different physiological effects, their structures are quite similar.
For example, the only difference between testosterone and
progesterone is the substituent at C-17, and the only difference
between androsterone and estradiol is one carbon and six
hydrogens, but these compounds make the difference between
being male and being female. These examples illustrate the
extreme specificity of biochemical reactions.
Synthetic unsteroid estrogens widely use in pharmacy then
steroid estrogens:
Progestins (gestagenes) — the pregnancy hormones,
hormones of yellow body. Maine hestagene hormone
is progesterone.
Aglycones of heart glycosides
• Heart glycosides in big doses very poisoned substances, in small – has
cardiotonic action. Heart glycosides according to its chemical structure are
O-glycosides, in which aglycone has steroid origin, carbohydrate fragment
represent by remainders of mono-, di-, tri- or tetrasaccharides.
• According to the character of lactone cycle heart glycosides divided on two
groups:
1). Cardenolids – contain at C17 fivemember unsaturated lactone cycle;
2). Buphadienolids – contain at C17 sixmember unsaturated lactone cycle;
Carbohydrate fragment can be represent by D-glucose, Dfructose, D-xylose, D-ramnose and also by
methylpentoses:
Heart glycosides of cardenolid group very often
contain as aglycones next compounds:
Example of such heart glycosides is
purpureaglycoside A
Aglycones of steroid saponines
Saponines – group of plant glycosides with high
surface activity, cases hemolysis of erythrocytes.
According to its chemical structure they are Oglycosides, in which aglycone has steroid or
triterpenoid origin. Most aglycones of steroid
saponines contain spiroketal fragment.
Many synthetic steroids have been found to be much more potent than
natural steroids. Norethindrone, for example, is better than progesterone in
arresting ovulation. Another synthetic steroid, RU 486, when taken along with
prostaglandins, terminates pregnancy within the first nine weeks of gestation.
Notice that these oral contraceptives have structures similar to that of rogesterone.
16. Water-soluble vitamins.
Thiamine
Pyridoxine
Niacin
Biotin
Riboflavin
Vitamin B12
The "antiscorbutic" factor of fresh fruits, which
prevents the development of the typical symptoms
of scurvy in humans, is a carbohydrate derivative
known as vitamin C or ascorbic acid.
17.Water insoluble (lipid-soluble) vitamines.
Thank you for attention!