THEME: Di- and THEME: Di- and ppolysaccharidesolysaccharides. . TerpenesTerpenes..

Lecture № 15

associate. prof. Ye. B. Dmukhalska, assistant. I.I. Medvid

OutlineOutline1.Oligosaccharides. 1.Oligosaccharides. 2. The following functions of carbohydrates in humans. 2. The following functions of carbohydrates in humans. Classification of disaccharides.Classification of disaccharides. 3. Polysaccharides (glucanes).3. Polysaccharides (glucanes).a) Homopolysaccharides:a) Homopolysaccharides:b) Heteropolysaccharides.b) Heteropolysaccharides.4. Glycoconjugates.4. Glycoconjugates. 5. 5. Lipids: Fats. Phospholipids. Lipids: Fats. Phospholipids. WaxesWaxes. . Nonsaponifiable lipids. Nonsaponifiable lipids. 6. Terpenes and terpenoids. 6. Terpenes and terpenoids. Terpene biosynthesis. Terpene biosynthesis. Classification of Classification of tterpeneserpenes..7. 7. CarotenoidsCarotenoids.. SteroidsSteroids. Properties of cholesterol.. Properties of cholesterol. Biosynthesis of Biosynthesis of ccholesterolholesterol..8. Vitamins.8. Vitamins. Water-soluble vitamins. Water insoluble (lipid-soluble) Water-soluble vitamins. Water insoluble (lipid-soluble) vitamins.vitamins.

Disaccharides. Disaccharides. А monosaccharide that has cyclic forms А monosaccharide that has cyclic forms (hemiacetal or hemiketal) can react with an alcoho1 to form а (hemiacetal or hemiketal) can react with an alcoho1 to form а glycoside (acetal or ketal). This same type of reaction can be glycoside (acetal or ketal). This same type of reaction can be used to produce а disaccharide, а carbohydrate in which two used to produce а disaccharide, а carbohydrate in which two monosaccharides are bonded together. In disaccharide formation, monosaccharides are bonded together. In disaccharide formation, one of the monosaccharide reactants functions as а hemiacetal or one of the monosaccharide reactants functions as а hemiacetal or hemiketal, and the other functions as an alcohol.hemiketal, and the other functions as an alcohol.

Monosaccharide + monosaccharide = disaccharide + НMonosaccharide + monosaccharide = disaccharide + Н22OO

The bond that links the two monosaccharides of а disaccharide together is called а glycosidic 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 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 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 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 disaccharides: maltose, cellobiose, lactose, and saccharose. As we consider details of the structures of these compounds, we will find that the configuration (of these compounds, we will find that the configuration (αα or or ββ) at carbon-1 of the reacting ) at carbon-1 of the reacting monosaccharides is often of prime importance. monosaccharides is often of prime importance.

MaltoseMaltose, often called malt sugar, is produced by , often called malt sugar, is produced by breaking down the polysaccharide starch, as takes place in breaking down the polysaccharide starch, as takes place in plants when seeds germinate and in human beings during plants when seeds germinate and in human beings during starch digestion. It is starch digestion. It is аа common ingredient in baby foods and is common ingredient in baby foods and is found in malted milk. Malt (germinated barley that has been found in malted milk. Malt (germinated barley that has been baked and ground) contains maltose; hence the name malt baked and ground) contains maltose; hence the name malt sugar. Structurally, maltose is made up of two D-sugar. Structurally, maltose is made up of two D-glucopyranose units, one of which must be glucopyranose units, one of which must be -D-glucose. The -D-glucose. The formation of maltose from two glucose molecules is as follows:formation of maltose from two glucose molecules is as follows:

-D-Glucose -D-Glucose -D-Glucose -D-Glucose -(1-4)-linkage -(1-4)-linkage

So, α-maltose can be named as 4-O-(α-D-glucopyranosido)-α-D-glucopyranose, β-maltose – 4-O-(α-D-glucopyranosido)-β-D-glucopyranose.

The glycosidic linkage between the two glucose units is called The glycosidic linkage between the two glucose units is called an an (1 - 4) linkage. The two ОН-groups that form the linkage (1 - 4) linkage. The two ОН-groups that form the linkage are attached, respectively, to carbon-1 of the first glucose unit are attached, respectively, to carbon-1 of the first glucose unit (in an a configuration) and to carbon-4 of the second. Maltose (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 is а reducing sugar, because the glucose unit on the right has а hemiacetal carbon atom (С-1).Thus this glucose unit can open hemiacetal carbon atom (С-1).Thus this glucose unit can open and close; it is in equilibrium with its open-chain aldehyde and close; it is in equilibrium with its open-chain aldehyde form. This means there are actually three forms of the maltose form. This means there are actually three forms of the maltose molecule: molecule: -maltose, -maltose, -maltose, and the open-chain form. In -maltose, and the open-chain form. In the solid state, the the solid state, the -form is dominant. The most important -form is dominant. The most important chemical reaction of maltose is hydrolysis. Hydrolysis of D-chemical reaction of maltose is hydrolysis. Hydrolysis of D-maltose, whether in а laboratory flask or in а living organism, maltose, whether in а laboratory flask or in а living organism, produces two molecules of D-glucose.produces two molecules of D-glucose.

O O

O O

O O

HH

H

HHH

H

HOOH

HO

CH2OH CH2OH

OHOH

OHOH

CH3J або (CH3)2SO4

(CH3CO)2O

(Ac = CH3CO)

HH

H

HHH

HOOCH3

CH3O

CH2OCH3CH2OCH3

OCH3OCH3

OCH3

HH

H

HHH

HOOAc

AcO

CH2OAc CH2OAc

OAcOAc

OAcOAc

H

H

H

H

H

OCH3

HOH, H+

HOH, H+

O O

O O

HOH, H+

HH

H

HHH

OOH

CH3O

CH2OCH3CH2OCH3

OCH3OCH3

OCH3

H

HOCH3

+ CH3OH

HOH, H+ HH H

HH

HOOH

AcO

CH2OAc CH2OAc

OAcOAc

OAcOAc H+ CH3COOH

H H

CellobioseCellobiose is produced as an intermediate in the is produced as an intermediate in the hydrolysis of the polysaccharide cellulose. Like maltose, hydrolysis of the polysaccharide cellulose. Like maltose, cellobiose contains two cellobiose contains two D-glucoseD-glucose monosaccharide units. It monosaccharide units. It differs from maltose in one of D-glucose units - the one differs from maltose in one of D-glucose units - the one functioning as а hemiacetal - must have а functioning as а hemiacetal - must have а -configuration -configuration instead of the а configuration of maltose. This change in instead of the а configuration of maltose. This change in configuration gives а configuration gives а (1-4) glycosidic linkage.(1-4) glycosidic linkage.

-D-Glucose (1-4)-linkage

α-cellobiose can be named as 4-O-(β-D-glucopyranosido)-α-D-glucopyranose, β-cellobiose – 4-O-(β-D-glucopyranosido)-β-D-glucopyranose.

Like maltose, cellobiose is a reducing sugar, has three Like maltose, cellobiose is a reducing sugar, has three isomeric forms in aqueous solution, and upon hydrolysis isomeric forms in aqueous solution, and upon hydrolysis produces two produces two D-glucoseD-glucose molecules. Despite these similarities, molecules. Despite these similarities, maltose and cellobiose have different biological behaviors. maltose and cellobiose have different biological behaviors. These differences are related to the stereochemistry of their These differences are related to the stereochemistry of their glycosidic linkages. glycosidic linkages. MaltaseMaltase, the enzyme that breaks the , the enzyme that breaks the glucose-glucose glucose-glucose (1-4) linkage present in maltose, is found (1-4) linkage present in maltose, is found both in the human body and in yeast. Consequently, maltose is both in the human body and in yeast. Consequently, maltose is digested easily by humans and is readily fermented by yeast. digested easily by humans and is readily fermented by yeast. Both the human body and yeast lack the enzyme Both the human body and yeast lack the enzyme cellobiasecellobiase needed to break the glucose - glucose needed to break the glucose - glucose (1-4) linkage of (1-4) linkage of cellobiose. Thus cellobiose cannot be digested by humans or cellobiose. Thus cellobiose cannot be digested by humans or fermented by yeast. In maltose and cellobiose, the two units of fermented by yeast. In maltose and cellobiose, the two units of the disaccharide are identical - two glucose units in each case. the disaccharide are identical - two glucose units in each case. Maltose and cellobiose have different arrangement in space. In Maltose and cellobiose have different arrangement in space. In maltose molecule maltose molecule αα-glycosidic linkage has axial arrangement, -glycosidic linkage has axial arrangement, in cellobiose molecule in cellobiose molecule ββ-glycosidic linkage – equatorial. Its -glycosidic linkage – equatorial. Its cases club-similar structure of amylose and linear structure of cases club-similar structure of amylose and linear structure of cellulose.cellulose.

LactoseLactose includes includes -D-galactopyranose unit and а D--D-galactopyranose unit and а D-glucopyranose unit joined by glucopyranose unit joined by -(1-4) glycosidic linkage-(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-D-fructofuranose.

Sucrose, unlike maltose, cellobiose, and Sucrose, unlike maltose, cellobiose, and lactose, is а non-reducing sugar. No helmiacetal lactose, is а non-reducing sugar. No helmiacetal or hemiketal center is present in the molecule, or hemiketal center is present in the molecule, because the glycosidic linkage involves the because the glycosidic linkage involves the reducing ends of both monosaccharides. Sucrose, reducing ends of both monosaccharides. Sucrose, in the solid state and in solution, exists in only in the solid state and in solution, exists in only one form - there are no one form - there are no and and isomers, and an isomers, and an open-chain form is not possible. Sucrose, the open-chain form is not possible. Sucrose, the enzyme needed to break the enzyme needed to break the ,,(1 - 2)(1 - 2) linkage in linkage in sucrose, is present in the human body. Hence sucrose, is present in the human body. Hence sucrose is an easily digested substance.sucrose is an easily digested substance.

dextrorotatory laevorotatory

Linear and branched structure Linear and branched structure of polysaccharidesof polysaccharides

HomopolysaccharidesHomopolysaccharides

Structure, composition and properties Structure, composition and properties

ofof ccellulose.ellulose.CelluloseCellulose is the most abundant polysaccharide. is the most abundant polysaccharide.

It is the structural component of the cell walls of It is the structural component of the cell walls of plants. Approximately half of all the carbon atoms in plants. Approximately half of all the carbon atoms in the plant kingdom are contained in cellulose the plant kingdom are contained in cellulose molecules. Structurally, cellulose is а linear molecules. Structurally, cellulose is а linear (unbranched) D-glucose polymer in which the (unbranched) D-glucose polymer in which the glucose units are linked by glucose units are linked by (1-4) glycosidic bonds.(1-4) glycosidic bonds.

• At heating with mineral acids cellulose At heating with mineral acids cellulose hydrolyzed by the following scheme:hydrolyzed by the following scheme:

In cellulose glucopyranose In cellulose glucopyranose remainders have linear structure and remainders have linear structure and hydrogen bonds:hydrogen bonds:

High-fiber food may also play а role in weight control. High-fiber food may also play а role in weight control. Obesity is not seen in parts of the world where people eat large Obesity is not seen in parts of the world where people eat large amounts of fiber-rich foods. Many of the weight-loss products amounts of fiber-rich foods. Many of the weight-loss products on the market are composed of bulk-inducing fibers such as on the market are composed of bulk-inducing fibers such as methylcellulose.methylcellulose.

FIGURE. FIGURE. Cellulose microfibrils.Cellulose microfibrils. • Some fibers bind lipids such as cholesterol Some fibers bind lipids such as cholesterol

and carry out them of the body with the and carry out them of the body with the feces. This lowers blood lipid concentrations feces. This lowers blood lipid concentrations and possibly the risk of heart and artery and possibly the risk of heart and artery disease.disease.

In amylose's structure, the glucose units are connected by In amylose's structure, the glucose units are connected by (1- 4) glycosidic linkages.(1- 4) glycosidic linkages.

Starch (amylose) Starch (amylose)

The number of glucose units present in an The number of glucose units present in an amyloseamylose chain chain depends on the source of the starch; 200 – 350 monomer units depends on the source of the starch; 200 – 350 monomer units are usually present. are usually present. AmylopectinAmylopectin, the other polysaccharide in , the other polysaccharide in starch, is similar to amylose, but has а high degree branched starch, is similar to amylose, but has а high degree branched structure in the polymer. А one branch link containe 20-25 structure in the polymer. А one branch link containe 20-25 glucose units. The number of glucose units present in an glucose units. The number of glucose units present in an amylopectin chain consists of 1000 and more units. The branch amylopectin chain consists of 1000 and more units. The branch points involve points involve (1 – 6) linkages:(1 – 6) linkages:

Starch (amylopectin)

Glycogen is an ideal storage form for glucose. The Glycogen is an ideal storage form for glucose. The large size of these macromolecules prevents them from large size of these macromolecules prevents them from diffusing out of cells. Also, conversion of glucose to glycogen diffusing out of cells. Also, conversion of glucose to glycogen reduces osmotic pressure. Cells would burst because of reduces osmotic pressure. Cells would burst because of increased osmotic pressure if all of the glucose in glycogen increased osmotic pressure if all of the glucose in glycogen were present in cells in free form. High concentrations of were present in cells in free form. High concentrations of glycogen in а cell sometimes cases precipitate or crystallize glycogen in а cell sometimes cases precipitate or crystallize into glycogen granules. These granules are discernible in into glycogen granules. These granules are discernible in photographs of cells under electron microscope magnification. photographs of cells under electron microscope magnification. The glucose polymers amylose, amylopectin, and glycogen The glucose polymers amylose, amylopectin, and glycogen compare as follows in molecular size and degree of branching:compare as follows in molecular size and degree of branching:

• Amylose:Amylose: Up to 1000 glucose units; no branching Up to 1000 glucose units; no branching• Amylopectin:Amylopectin: Up to 100,000 glucose units; branch points Up to 100,000 glucose units; branch points

every 20-25 glucose unitsevery 20-25 glucose units• Glycogen:Glycogen: Up to 1,000,000 glucose units; branch points every Up to 1,000,000 glucose units; branch points every

8-12 glucose units8-12 glucose units

Because of the branching, amylopectin has а Because of the branching, amylopectin has а larger average molecular mass than the linear larger average molecular mass than the linear amylose. The average molecular mass of amylose is amylose. The average molecular mass of amylose is 40000 or more; it is 1-6 mln. for amylopectin. Note 40000 or more; it is 1-6 mln. for amylopectin. Note that all of the glycosidic linkages in starch (both that all of the glycosidic linkages in starch (both amylose and amylopectin) are of the amylose and amylopectin) are of the -type. In -type. In amylose, they are all amylose, they are all (1 - 4); in amylopectin, both (1 - 4); in amylopectin, both (1 -4) and (1 -4) and (1 -6) linkages are present. Because а (1 -6) linkages are present. Because а linkages can be broken through hydrolysis within the linkages can be broken through hydrolysis within the human digestive tract (with the help of the enzyme human digestive tract (with the help of the enzyme amylase), starch has nutritional value for humans. amylase), starch has nutritional value for humans. The starches present in potatoes and cereal grains The starches present in potatoes and cereal grains (wheat, rice, corn, etc.) account for approximately (wheat, rice, corn, etc.) account for approximately two-thirds of the world' s food consumption.two-thirds of the world' s food consumption.Fermentayion hydrolysis of starch is shown below:Fermentayion hydrolysis of starch is shown below:

FIGURE. FIGURE. Structure of amylopectine ( Structure of amylopectine (аа), glycogen (b) ), glycogen (b)

DextranesDextranes• Dextranes Dextranes have bacterial origin, contain remainders of have bacterial origin, contain remainders of αα--

D-glucopyranoseD-glucopyranose. Dextranes obtain from sucrose at the . Dextranes obtain from sucrose at the present of bacterium (Leuconostoc mesenteroides). The present of bacterium (Leuconostoc mesenteroides). The main type of bond is main type of bond is αα-1,6-glycosidic bond, in place of -1,6-glycosidic bond, in place of branching – branching – αα-1,4- and -1,4- and αα-1,3-glycosidic bonds. -1,3-glycosidic bonds. The average The average molecular mass of dextranes is few millions. Partly hydrolyzed dextranes molecular mass of dextranes is few millions. Partly hydrolyzed dextranes (m. m. – 40000-800000) use in pharmacy as plasmasubstitute (m. m. – 40000-800000) use in pharmacy as plasmasubstitute (“Polyglucin”, “Reopolyglucin”). (“Polyglucin”, “Reopolyglucin”).

InulineInuline• Inuline – reserve polysaccharide, present Inuline – reserve polysaccharide, present

in plants. Inuline has linear structure and in plants. Inuline has linear structure and consists of remainders of consists of remainders of ββ-D--D-fructofuranosefructofuranose, joined by 2,1-, joined by 2,1-glycosidic bonds, in the end of inuline is glycosidic bonds, in the end of inuline is αα-D-glucopyranose remainder (like -D-glucopyranose remainder (like sucrose). Msucrose). Molecular mass of inuline is up olecular mass of inuline is up to 6000. Use for obtaining of D-fructose.to 6000. Use for obtaining of D-fructose.

Pectin compoundsPectin compounds

• Pectin compounds (pectins) – Pectin compounds (pectins) – polysaccharides consist of polysaccharides consist of polygalacturonic acid, which contain polygalacturonic acid, which contain remainders of remainders of αα-D-galacturonic -D-galacturonic acidacid joined by 1,4-glycosidic bonds. joined by 1,4-glycosidic bonds. Part of carboxyl grups present in Part of carboxyl grups present in appearance of methyl ether. Water appearance of methyl ether. Water solutions of pectins form stable gels. solutions of pectins form stable gels. Pectins have antiulcer properties.Pectins have antiulcer properties.

It is а highly viscous substance and has а molecular weight It is а highly viscous substance and has а molecular weight in several hundred millions. in several hundred millions. Hyaluronic acidHyaluronic acid is а principal is а principal component of the ground substance of connective tissue. Among component of the ground substance of connective tissue. Among other places it is found in skin, synovial fluid, vitreous hemour of other places it is found in skin, synovial fluid, vitreous hemour of the eye, and umbilical cord. It exercises а cementing function in the the eye, and umbilical cord. It exercises а cementing function in the tissues and capillary walls, and forms а coating gel round the ovum. tissues and capillary walls, and forms а coating gel round the ovum. It accounts for about 80% of the viscosity of synovial fluid which It accounts for about 80% of the viscosity of synovial fluid which contains about 0. 02 – 0.05% of hyaluronate. Repeat part of contains about 0. 02 – 0.05% of hyaluronate. Repeat part of hyaluronic acid is hyaluronic acid is D-glucuronic acid and N-acetyl-D-D-glucuronic acid and N-acetyl-D-glucosamineglucosamine joined by joined by ββ--1,31,3-glycosidic bond, between -glycosidic bond, between disaccharide fragments – disaccharide fragments – ββ-1,4-1,4. Molecular mass of . Molecular mass of hyaluronic acid hyaluronic acid is from 1600 to 6400.is from 1600 to 6400.

(1,4)-O-(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy--D-glucopyranose.-D-glucopyranose.

Chondroitin sulfate.Chondroitin sulfate. It has similar structure as hyaluronic It has similar structure as hyaluronic acid with the difference that the N-acetyl-D-glucosamine unit of the acid with the difference that the N-acetyl-D-glucosamine unit of the molecule is replaced by N-acetyl-D-galactosamine unit with molecule is replaced by N-acetyl-D-galactosamine unit with sulphate group. Repeat part of chondroitin sulphate is D-glucuronic sulphate group. Repeat part of chondroitin sulphate is D-glucuronic acid and N-acetyl-D-galactosamine which contains sulfate group. acid and N-acetyl-D-galactosamine which contains sulfate group. Inside of disaccharide fragment is Inside of disaccharide fragment is ββ-1,3-glycosidic bond; between -1,3-glycosidic bond; between fragments – fragments – ββ-1,4. Sulfate group forms ether bond with hydroxyl -1,4. Sulfate group forms ether bond with hydroxyl group of group of N-acetyl-D-galactosamine in location 4 (N-acetyl-D-galactosamine in location 4 (chondroitin-4-chondroitin-4-sulfatesulfate) or in location 6 () or in location 6 (chondroitin-6-sulfatechondroitin-6-sulfate). Chondroitin ). Chondroitin sulfates are found in cartilage, bone, heart valves, tendons and sulfates are found in cartilage, bone, heart valves, tendons and cornea.cornea.

(1,4)-O-(1,4)-O--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo--D-Glucopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-6-O-sulfo---D-galactopyranose.D-galactopyranose.

Hydrocarbon chains of chondroitin-4-sulfate chondroitin-4-sulfate contain up to 150 disaccharides remainders, contain up to 150 disaccharides remainders, joined in organism by O-glycosidic bonds with joined in organism by O-glycosidic bonds with hydroxyl groups of aminoacid remainders. hydroxyl groups of aminoacid remainders.

Dermatan sulfateDermatan sulfate. (Varying amounts of D-. (Varying amounts of D-glucuronic acid may be present. Concentration glucuronic acid may be present. Concentration increases during aging process.)increases during aging process.)

(1,4)-O-(1,4)-O--L-idopyranosyluronic acid-(1,3)-2--L-idopyranosyluronic acid-(1,3)-2-acetamino-2-dezoxy-4-O-sulfo-acetamino-2-dezoxy-4-O-sulfo--D--D-

galactopyranose. galactopyranose.

Heparin.Heparin. It is naturally occurring anticoagulant found It is naturally occurring anticoagulant found mainly in the liver, and also in lung, spleen, kidney and intestinal mainly in the liver, and also in lung, spleen, kidney and intestinal mucosa. It prevents blood clotting by inhibiting the prothrombin-mucosa. It prevents blood clotting by inhibiting the prothrombin-thrombin conversion and thus eliminating the thrombin effect on thrombin conversion and thus eliminating the thrombin effect on fibrinogen. Repeat part of heparin consists of fibrinogen. Repeat part of heparin consists of D-glucosaminD-glucosamin and and uronic aciduronic acid, joined by , joined by αα-1,4-glycosidic bonds. As uronic acid in -1,4-glycosidic bonds. As uronic acid in heparin present heparin present L-iduronic acidL-iduronic acid or, very rare, D-glucuronic acid. or, very rare, D-glucuronic acid. Remainders of glucosamine and L-iduronic acid partly sulfonated.Remainders of glucosamine and L-iduronic acid partly sulfonated. Molecular mass of Molecular mass of heparin is 16000-20000.heparin is 16000-20000.

(1,4)-O-(1,4)-O--D-idupyranosyluronic acid-2-O-sulfo--D-idupyranosyluronic acid-2-O-sulfo-(1,4)-2-sulfamino-2-dezoxy-6-O-sulfo-(1,4)-2-sulfamino-2-dezoxy-6-O-sulfo--D--D-glucopyranoseglucopyranose

FigFig.. Proteoglycan structure Proteoglycan structure

Mucin-type carbohydrate Mucin-type carbohydrate While all N-linked While all N-linked oligosaccharides are bound to protein via GlcNAc-Asn, the oligosaccharides are bound to protein via GlcNAc-Asn, the linking groups of O-glycosidic oligosaccharides are of several linking groups of O-glycosidic oligosaccharides are of several types. The most common of these is GalNAc-Ser (or GalNAc-types. The most common of these is GalNAc-Ser (or GalNAc-Thr). Considerable mucin-type carbohydrate unit is Thr). Considerable mucin-type carbohydrate unit is disaccharide such as Gal-1,3-GalNAc, found in the antifreeze disaccharide such as Gal-1,3-GalNAc, found in the antifreeze glycoprotein of antarctic fish (Figure), to the complex glycoprotein of antarctic fish (Figure), to the complex oligosaccharides of blood groups such as those of the ABO oligosaccharides of blood groups such as those of the ABO system.system.

Fig. Antifreeze glycoprotein structure.Fig. Antifreeze glycoprotein structure.

6. Lipids6. LipidsLipids 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 lipidsClassification of lipids

Lipids are organic compounds, found in living Lipids are organic compounds, found in living organisms, that are soluble in nonpolar organic solvents. organisms, that are soluble in nonpolar organic solvents. Because compounds are classified as lipids on the basis of a Because compounds are classified as lipids on the basis of a physical property— their solubility in an organic solvent—physical property— their solubility in an organic solvent—rather than as a result of their structures, lipids have a rather than as a result of their structures, lipids have a variety of structures and functions, as the variety of structures and functions, as the following following examples illustrate: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 Nomenclature, methods of getting of fatsgetting of fats

Methods of getting:Methods of getting:

1.1. O-acylation of alcohols;O-acylation of alcohols;

2.2. Allocation from plants: melting out, pressing or Allocation from plants: melting out, pressing or extraction by organic solvents.extraction by organic solvents.

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.

The most widespread fatty The most widespread fatty acids in natural oils and fats:acids in natural oils and fats:

Double bonds are rigid structures, unsaturared acid Double bonds are rigid structures, unsaturared acid molecules that contain them can occur in two isomeric forms: molecules that contain them can occur in two isomeric forms: ciscis and and transtrans. In cis-isomers, for example, similar or identical groups . In cis-isomers, for example, similar or identical groups are on the same side of double bond (a). When such groups are on 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-opposite sides of a double bond, the molecule is said to be a trans-isomer (b):isomer (b):

The double bonds in unsaturated fatty acids generally have the The double bonds in unsaturated fatty acids generally have the cis cis configurationconfiguration. This configuration produces a bend in the molecules, which . This configuration produces a bend in the molecules, which prevents them from packing together as tightly as fully saturated fatty prevents them from packing together as tightly as fully saturated fatty acids. As a result, unsaturated fatty acids have fewer intermolecular acids. As a result, unsaturated fatty acids have fewer intermolecular interactions and, therefore, lower melting points than saturated fatty acids interactions and, therefore, lower melting points than saturated fatty acids with comparable molecular weights . The melting points of the unsaturated with comparable molecular weights . The melting points of the unsaturated fatty acids decrease as the number of double bonds increases. For example, 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 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 one double bond, at if it has two -5 °C o double bonds, and at -11 °C if it has three double bonds.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.

HydrolysisHydrolysis of а of а triacylglycerol triacylglycerol

HydrolysisHydrolysis of а triacylglycerol is the of а triacylglycerol is the reverse of the esterification reaction reverse of the esterification reaction by which it wet formed. Complete by which it wet formed. Complete hydrolysis of а triacylglycerol hydrolysis of а triacylglycerol molecule always gives one glycerol molecule always gives one glycerol molecule and three fatty acid molecule and three fatty acid molecules as products.molecules as products.

7. Chemical properties of 7. Chemical properties of fats fats

1). 1). Hydrolysis of fats with alkaliHydrolysis of fats with alkali (e.g., sodium hydroxide) yields salts of the (e.g., sodium hydroxide) yields salts of thefatty acids, and those of the alkali metals, such as sodium or potassium, are fatty acids, and those of the alkali metals, such as sodium or potassium, are useuseigig as soaps as soaps. Another name of this reaction – “saponification”. 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. 2). Oxidation of fates. Oxidation cases rancidity Oxidation cases rancidity of fates. During oxidation form aldehydes with short of fates. During oxidation form aldehydes with short carbon chain.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). 3). HydrogenationHydrogenation.. Some or all of the double bonds of Some or all of the double bonds of

polyunsaturated oils can be reduced by catalytic hydrogenation. Margarine polyunsaturated oils can be reduced by catalytic hydrogenation. Margarine and shortening are prepared by hydrogenating vegetable oils such as soybean and shortening are prepared by hydrogenating vegetable oils such as soybean oil and sunflower oil until they have the desired consistency. This process is oil and sunflower oil until they have the desired consistency. This process is called “hardening of oils.” The hydrogenation reaction must be carefully called “hardening of oils.” The hydrogenation reaction must be carefully controlled, however, because reducing all the carbon–carbon double bonds controlled, however, because reducing all the carbon–carbon double bonds would produce a hard fat with the consistency of beef tallow. would produce a hard fat with the consistency of beef tallow. Quantity of H2 Quantity of H2 in grams, which are necessary for hydration of 10kg of fats in grams, which are necessary for hydration of 10kg of fats ((hydration numberhydration number) characterizes unsaturating of fat.) characterizes unsaturating of fat.

4). Addition of halogens. 4). Addition of halogens.

Iodine number for plants fats – 100-200, for Iodine number for plants fats – 100-200, for animal fats – 25-86, for fish fats – 100-193.animal fats – 25-86, for fish fats – 100-193.

As might be expected from the properties of the fatty acids, As might be expected from the properties of the fatty acids, fats have a predominance of saturated fatty acids, and oils are fats have a predominance of saturated fatty acids, and oils are composed largely of unsaturated acids. Thus, the melting points of composed largely of unsaturated acids. Thus, the melting points of triglycerides reflect their composition, as shown by the following triglycerides reflect their composition, as shown by the following examples. Natural mixed triglycerides have somewhat lower melting examples. Natural mixed triglycerides have somewhat lower melting points, the melting point of lard being near 30 º C, whereas olive oil 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 melts near -6 º C. Since fats are valued over oils by some Northern European and North American populations, vegetable oils are European and North American populations, vegetable oils are extensively converted to solid triglycerides (e.g. Crisco) by partial extensively converted to solid triglycerides (e.g. Crisco) by partial hydrogenation of their unsaturated components. Some of the hydrogenation of their unsaturated components. Some of the remaining double bonds are isomerized (to trans) in this operation. remaining double bonds are isomerized (to trans) in this operation. These saturated and trans-fatty acid glycerides in the diet have been These saturated and trans-fatty acid glycerides in the diet have been linked to long-term health issues such as atherosclerosis.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. Phosphorus-containing 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 Classification of phospholipidsphospholipids

Washing action of soapsWashing action of soaps

WaxesWaxes 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 lipids9. Nonsaponifiable lipids 1). Prostaglandins – physiologically 1). Prostaglandins – physiologically

active substances with biogenic active substances with biogenic origin, stimulate smooth muscles and origin, stimulate smooth muscles and lowers blood pressure. All lowers blood pressure. All prostaglandins contain carboxyl prostaglandins contain carboxyl group and 20 carbon atoms in group and 20 carbon atoms in molecule, they are derivatives of molecule, they are derivatives of eyicosanic acid.eyicosanic acid.

All the prostaglandins are 20-carbon carboxylic acids and contain a cyclopentane ring. All have hydroxyl groups at C-11 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 Prostaglandins have cyclopentane ring. According to allocation of double bonds in fivemember cycle and side chains prostaglandins double bonds in fivemember cycle and side chains prostaglandins marked by litters A, B, C, D, E and F.marked by litters A, B, C, D, E and F.

According to the number of double bonds in side chains every According to the number of double bonds in side chains every group of prostaglandins divided on series that marked as group of prostaglandins divided on series that marked as indexes.indexes.

In the names ofIn the names of prostaglandins orientation of prostaglandins orientation of hydroxyl group in location 9 according to the hydroxyl group in location 9 according to the carbon chain at C8 mark carbon chain at C8 mark αα or or ββ. . αα – means cis- – means cis-configuration, configuration, ββ – trance. – trance.

2). 2). Isoprenoides – products of isoprene Isoprenoides – products of isoprene transformation. Some vitamins and hormones transformation. Some vitamins and hormones have isoprenoides structure.have isoprenoides structure.

Isoprenoides includes terpens, carotinoids and steroidsIsoprenoides includes terpens, carotinoids and steroids

The following scheme shows how some of the many The following scheme shows how some of the many monoterpenes could be synthesized monoterpenes could be synthesized from geranyl from geranyl pyrophosphate: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.

MonoterpensMonoterpensThey are the terpenes that have been known for several They are the terpenes that have been known for several

centuries as components of the fragrant oils obtained from centuries as components of the fragrant oils obtained from leaves, flowers and fruits. Monoterpenes, with sesquiterpenes, leaves, flowers and fruits. Monoterpenes, with sesquiterpenes, are the main constituents of essential oils.are the main constituents of essential oils.

Acyclic monoterpens:Acyclic monoterpens:They can be considered as derivatives of 2,6-dimethyloctane. They can be considered as derivatives of 2,6-dimethyloctane.

In the basis of carbon skeleton In the basis of carbon skeleton acyclic acyclic monoterpens are structures of isoprene monoterpens are structures of isoprene isomeric dimers: myrcene and ocimene.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 Among natural molecules, the followings are well known and have several structural isomers.known and have several structural isomers.

Geraniol and citral present in ether oils, especially in citric oil. They are pheromones.

Monocyclic monoterpenesMonocyclic monoterpenes They are derived from cyclohexane with an isopropyl They are derived from cyclohexane with an isopropyl

substituent. substituent. The mostThe most important members are limonene important members are limonene and methane.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 limoneneCatalytically hydrogenisation of limonene

– – hydratation of limonene:hydratation of limonene:

Menthane (1-isopropilmethylbenzol) is obtained from p-cimol (n-isopropilmethylbenzol) hydration.

From hydroxyderivatives of menthane most important is From hydroxyderivatives of menthane most important is menthol (menthanol-3), which has tree asymmetric menthol (menthanol-3), which has tree asymmetric centers. (-)Menthol synthesized by reducing of centers. (-)Menthol synthesized by reducing of menthone.menthone.

(+)Menthol in industry synthesized by alkylation of m-crezol with following (+)Menthol in industry synthesized by alkylation of m-crezol with following hydration of tymol.hydration of tymol.

Menthol has antiseptic, sedative, analgesic properties (Boromenthol, Pectussine)

Terpinehydrate (monohydrate Terpinehydrate (monohydrate menthandiol-1,8) use in medicine in menthandiol-1,8) use in medicine in treatment of chronic bronchitis. treatment of chronic bronchitis.

Bicyclic monoterpenes: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:

αα-Pinene contains in turpentine oil – -Pinene contains in turpentine oil – turpentine (up to 75 %). turpentine (up to 75 %).

Heating with dilute acids (H2SO4, HNO3):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 borneolSynthesis of difficult esters of borneol

Oxidation by chromic acid:

Interaction between borneol and acids:

Camphene can hydrolyze in acidic medium with Camphene can hydrolyze in acidic medium with formation of isoborneol.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 synthesisTishchenko synthesis

Methylene group in α-location (according to carbonyl group) has CH-acidic properties.

Oxidation of camphor with nitrate acid

Carotene – yellow-red pigment, contains Carotene – yellow-red pigment, contains in carrot, milk and butter. Carotene is a in carrot, milk and butter. Carotene is a mixture of tree isomers – mixture of tree isomers – αα-, -, ββ- and - and γγ--carotene.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.

SterinesSterines (sterols) – steroid alcohols, which contain in basis structure cholestane. Sterines are 3-hydroxyderivatives 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 In lipids of human skin cholesteol transforms in vitamin D3 (cholecalciferrol) at the presents of UF-light. (cholecalciferrol) at the presents of UF-light.

ErgosterineErgosterine (ergosterol, 24-methylcholestanetrien-5,7,22-ol- (ergosterol, 24-methylcholestanetrien-5,7,22-ol-33ββ) refers to mycosterine group.) refers to mycosterine group. At the presents of UF-light At the presents of UF-light ergosterol isomerizes in vitamin Dergosterol isomerizes in vitamin D2 2 (ergocalciferrol)(ergocalciferrol)

Bile acidsBile 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 Bile acids exist in organism in connection with glycine aminoacid NH2CH2COOH or taurine NH2CH2CH2SO3H.aminoacid NH2CH2COOH or taurine NH2CH2CH2SO3H.

Steroid hormones Steroid hormones • Steroid hormones include 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 anti-inflammatory 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 In medicine also use synthetic analogs of hydrocortisone and analogs of hydrocortisone and cortisone – prednisolone, prednisone, cortisone – prednisolone, prednisone, dexamethasone, triamcinolone. dexamethasone, triamcinolone. These substances are more active These substances are more active then natural cthen natural corticoorticosteroids.steroids.

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. 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 Synthetic unsteroid estrogens widely use in pharmacy then steroid estrogens: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, D-fructose, D-xylose, D-ramnose and also by methylpentoses:

Heart glycosides of cardenolid group very often contain as aglycones next compounds:

Example of such hExample of such heart glycosides is eart glycosides is

purpureaglycoside Apurpureaglycoside A

Aglycones of steroid saponinesSaponines – group of plant glycosides with Saponines – group of plant glycosides with

high surface activity, cases hemolysis of high surface activity, cases hemolysis of erythrocytes. erythrocytes. According to its chemical According to its chemical structure they are O-glycosides, in which structure they are O-glycosides, in which aglycone has steroid or triterpenoid origin. aglycone has steroid or triterpenoid origin. Most aglycones of steroid saponines Most aglycones of steroid saponines contain spiroketal fragment.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.16. Water-soluble vitamins.

Thiamine

Pyridoxine

Niacin

Biotin

Riboflavin

Vitamin B12Vitamin 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.17.Water insoluble (lipid-soluble) vitamines.

Thank you for attention!