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MedChem Midterm 3 > Carbohydrates 1 > Flashcards

Carbohydrates 1 Flashcards

1
Q

Physical Properties of Carbohydrates

A

Derived from chemical structure

  • Polar molecules: large # of -OH groups - H-bond w/ wanter
  • High solubility in aqueous media
    • –> High Viscosity = suitable for thickeners (syrups/suspensions)
  • High solubility in water –> HYDROSCOPIC
    • CB’s are suitable as humectants and laxatives
  • Insoluble in organics
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2
Q

Physical Properties of carbohydrates

Viscosity

A

Viscosity Increases w/ # of Cabohydrate residues

(not strictly additive)

Raffinose > Sucrose > Glucose

  • Viscosity is related to # of Hydrogen bonds​ the molecule makes with the SOLVENT
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3
Q

Reduced Monosaccharides

A
  • Done Catalytically (hydrogen + catalyst)
    • or enzymatically
  • Product = Sugar Alcohol (Alditol, a polyol)
  • Ex.
    • Mannose –> Mannitol
    • Glyceraldyhyde –> Glycerol
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4
Q

Reducing Glucose

(monosaccharide)

A

Sorbitol (glucitol)

(a sugar alcohol)

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5
Q

Reducing Mannose

(monosaccharide)

A

Mannitol & Sorbitol

(sugar alcohols)

mannose also reduced to mannitol

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6
Q

Mannitol

A

Used as an Osmotic Diuretic

reduced form of Mannose

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7
Q

Glycerol

A

Hydroscopic = Humectant / Thickener

can be NITRATED –> Nitroglycerin

reduced from Glyceraldehyde

used in CIGARRETES –> cig burns longer

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8
Q

Sorbitol = Glucitol

A

Laxative
reduced from Glucose

  • can be dehydrated into:
    • tetrahydropyrans
    • tetrahydroFURAN compounds
      • (sorbitans)
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9
Q

Sorbitans

A

Can be converted to Detergents

Spans & Tweens

used in Emulsification procedueres

  • dehydrated product of sorbitol (glucitol), a laxative
  • can further be dehydrated into:
    • 1,4,3,6-dianhydro-D-sorbitol = ISOSORBIDE
    • isosorbide nitrated to –> ISDN / ISMN
      • treatment of angina
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10
Q

Isosorbide

ISDN / ISMN

A

1,4,3,6-dianhydro-D-sorbitol

formed by dehydration of sorbitol (glucitol)

glucose -> sorbitol(glucitol) -> isosorbide

a Diuretic

  • NITRATION –> ISDN / ISMN
    • ​treatment of ANGINA
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11
Q

Osmotic Diuretics

A

Mannitol & Isosorbide

  • slow or non-metabolized carb derivatives
  • sequester h2o for hydration
    • IV admin -> draw water from interstitial spaces
    • INCREASE osmolarity of blood
  • ​Expand plasma volume –> Increase urine volume
  • Also used to
    • Decrease intacranial (hydrocephalus)
      • ​& Intraocular (glaucoma) pressure
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12
Q

Spans & Tweens

A

Tetrahydrofuran formed by Sorbitans

Mild Detergents / Excipient / Emulsifyer

Spans = W/O

Tweens = O/W

  • Polysorbate 80
    • ​food emulsifyer (ice cream)
    • excipient to stabilize formations for parenteral admin.
  • Eye Drops / Vaccines
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13
Q

Glycosides

Acetals / Ketals

A

Hemiacetal + Alcohol = Acetal + h2o

Hemiketal + alcohol = Ketal +h2o

  • Require either strong acidic conditions
    • or/and a very good leaving group
      • =conjugate acid has a small pKa
  • Glycoside = Surgar acetal /ketal
    • OXOCABENIUM CATION
    • Can occur at either side of plane
      • ALPHA = TRANS
      • BETA = CIS
        • less enzymes in body to break down beta
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14
Q

Glycosides

Alpha vs Beta

A

Alpha = Trans

Beta = Cis

less enzymes to break down beta

Sugar acetal/ketals = glycosides

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15
Q

Glycoside:

Salicin

A

constituent of willow bark

analgesic / anti-inflammatory

metabolizes –> Salicylic acid

Glucose = Glycone

ArOH = A-Glycone

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16
Q

Glycosides:

Glycone Vs A-Glycone

A

Glycoside has 2 parts

Glycone = Glucose part

A-Glycone = ArOH part

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17
Q

Fruranose

A

hexofuranase (5) form (cyclic form) of a glucose/fructose

Is in equilibrium with pyronose

is the MORE UNSTABLE FORM

Increasing temperature –> more furanose

LESS SWEET than pyronose

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18
Q

Pyronose

A

6 membered ring form of fructose/glucose

MORE STABLE than furanose form

SWEETER FORM

when it is COLD, there is more Pyranose

–> why fruit juices are sweeter when it’s cold

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19
Q

other Glycosides

Amygdalin / Ouabain / Quercetrin

A
  • Amygdalin (vitamin B-17)
    • Bitter almonds / prunes / apricot
  • Ouabain = Cardiac Glycoside
    • Na/K pump inhibitor –> angina
    • contains L-rhamnose (sugar)
  • Quercetrin = flavonoid
    • Active Dye
    • antioxident properties
    • Kinase Inhibitor (L-rhamnose)
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20
Q

High Fructose Corn Syrup

HFCS

A
  • Unatural sweetener made from corn starch
    • by degradation w/ glycosidases
  • ​Has fructose-glucose ratio similar to HONEY
  • Fructose –> does not give the sensation of fullness unlike glucose
    • Fructose PROMOTES food intake
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21
Q

Fructose (Alketose)

vs

Glucose

A
  • Glucose –> sensation of fullness / satiety
  • Fructose –> promotes food intake
    • striatum / hypothalamus did not deactive during fructose ingestion
    • Reward pathway –> “percieved sweetness” of fructose is more than glucose
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22
Q

T1R Receptors

A
  • Carbohydrates & Artificial Sweetners bind to the same receptors
  • T1R2 / T1R3
    • ​G-coupled receptors (guanylate cclase)
  • Some sweeteners (SACCHARIN) bind to other receptors (NOICECEPTORS)
    • ​–> BITTER AFTERTASTE
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23
Q

Sucralose

= Splenda

A

Halogenated (Chlorinated) form of Sucrose

  • bind to GPCR-type receptors T1R-2, with GREATER affinity than sucrose
  • Only sparingly absorbed in GI
  • NOT METABOLIZED
    • not degraded metabolicly by glucosalses
    • compared to DDT (chlornated pesticide)
    • –> very low calories
  • FDA SAFE
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24
Q

Cyclamate

A
  • artificial sweetener
  • Discovered by student accidentally
  • Banned due to causing BLADDER Cancer in RATS
  • ​​
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25
Q

Saccharin

A
  • Artificial sweetener
  • UNSTABLE when heated (not good for baking)
  • Suspected to cause bladder cancer
    • Due to it doing so in RATS
    • –> did not occur in humans
  • Not metabolized in GI
  • ZERO calories = Suitable for diabetics
26
Q

Steviol

Truvia

A

Glycoside of Stevia

  • 300x sweeter than sugar BUT has BITTER aftertaste
  • used for diabetics
27
Q

Positive Role of Artificial Sweeteners

A
  • Obesity
    • ​easily metabolized, few or no calories
  • Diabetes
    • ​Sugar intace can be controlled
    • ~not straightforward can cause hyperinsulinemia
  • Reactive Hypoglycemia
    • ​reduce absorption of glucose into blood stream –> rapid releases of insulin
      • –> lead to hypoglycemia
  • Dental Care
    • ​artificial sugards do NOT adhere to enamel & feed bacteria
28
Q

Sugar Code

A
  • Monosaccharides can be combbined in MANY ways.
    • Each hydroxyl group can have glycosidic bond at each connection point
      • ALPHA OR BETA
    • LINEAR OR BRANCHED
  • LECTINS
    • proteins that bind specifically to oligosaccharide motifs and are the ones READING the information of the sugar code
29
Q

Lactulose

(Chronulac)

Galactose-b-(1,4)-fructose

A

semi-synthetic ​disaccharide

Ammonia Reducer / LAXATIVE

  • Works by inreasing water content / volume of stools in bowel
    • ​not absorbed in GI tract
  • ​​Metabolized in distal ilium / colon by BACTERIA to form:
    • lactic acid / formic acid / acetic acid
    • neutralizes ammonia (that causes encephalopathy)
      • –> used in management of encephalopathy
  • Safe to use EXCEPT for patients w/ b-galatoside deficiency
30
Q

Glycocalylx

A

10-100nm thick layer of complex glycans

cover all cells

  • Carbohydrates for recognition & communication
  • Decoded by carb binding proteins involved in pathological process
    • ex. recognition of viruses
31
Q

Carbohydrate Based Drugs

A
  • Main Areas:
    • Inhibition of glycolytic Enzymes (obesity)
    • Inhibition of glycoside binding proteins (infections)
  • Multivalent interaction is NOT an approach
    • ​requires HIGH MW reagents
    • contradicts LIPINSKI’s rules
32
Q

Problems W/ Carbohydrate Drugs

A
  • Carbs have low affinity as protein ligands
  • High Polarity​
    • ​cant pass through enterocyte layer of small intestine)
  • Fast Metobilites
  • binding sites are filled with water
    • Unless large # of water is displaced
    • the free energy formation is SMALL
      • HB interactions of water and sugar are similar
  • Designing a drug involves appendign charged residues
33
Q

Carbohydrate-Based Drugs

Alpha Amylase Inhibitors (AAI)

A

​Reduce Postprandial HYPERglycemia

  • Seek targets within the GI tract & structural mods can be made to:
    • REDUCE polarity
    • SLOW DOWN Metabolism
  • ​Effective in treatment of T2Diabetes
  • Iminosugars are effective AAI therapy
    • Miglitol (Glyset)
    • Voglibose(Glustat)
34
Q

Miglitol (Glyset)

Voglibose(Glustat)

A

Alpha Amylase Inhibitors

  • Iminosugars, carb-based drugs
  • Miglitol is a transition state analog inhibitor
    • Nitrogen(-) –> Oxocarbenium cation
    • in the glycosidase reaction
35
Q

Oseltamivir (Tamiflu)

Zanamavir

A

Antiviral (flu A/B) Drugs

Inhibit Viral Neuraminidase

  • Carb-based drug
  • Start @ Sialic Acid (N-acetylneuramic Acid)
    • ​substrate of Viral Neuraminidase
    • Inhibiting this enzyme prevents virus escape
  • ​​​​Zanamivir adds guanidine & carboxyl residue to oseltamivir
    • establishing salt-bridge type of interaction w/ active site
    • Example of drug affinity increased by fuctional group modification
36
Q

Inulin

A
  • a Fructan, polymer of fructose
    • bears a terminal a-1 linked glucose residue on the aglycon end
  • Not metabolized by human glycosidases
    • ​= soluble dietary fiber
    • broken down by bacteria in lower gi tract
  • ​Probiotic (PREBIOTIC)
    • ​stimulates growth of sprophytic bacteria
      • not degraded by human enzymes, is a nutrient to bacteria
  • Vaccination Ajuvant
    • Inulin activates immune response
      • Enhances immune response to vaccine
    • Also used in complex w/ aluminum salts (Algamulin)
  • weakly sweet sugar <25% of starch energy
  • Distributed in Chicory, Banana, Onion, Artichoke
  • Soluble in water
37
Q

Fiber

A
  • Carbohydrates that are NOT BROKEN DOWN or Absorbed by human digestive tract
    • Dietary fiber –> support digestive process
  • Ex. Inulin
    • ​broken down in lower GI by bacteria
    • result in flatulence & bloating
38
Q

a-mannoside motif

A

adjunct therapy with antibiotics for UTI’s

  • Cranberry juice contain a-mannosides @ high concentration
  • A-mannosides & FimH Lectin of the bacteria mediate the interaction between:
    • E.Coli -> urinary cells
      • via Fimbral adhesion proteins
      • displayed on bacterial surface, act as ANCHORS
39
Q

Keyhole Limpet Hemocyanin

KLH protein

A
  • = Vaccine carrier protein that is immunogenic yet safe in humans
  • Used for SYNTHETIC VACCINES
    • carbohydrate antigen is determined
    • Antigen is ligated –> polypeptide
      • To provide IMMUNOGENIC component of vaccine
        • ability to provoke immune response
    • considered safer than weakened bacteria
  • Issues:
    • ​low immunogenicity due to low antigenic mimicry by glycans
40
Q

Cyclodextrin

CD’s

A

Used in Drug Delivery

  • cyclic a(1,4)-linked glycans
    • containing 6-8 glucose residues (a, b and g).
  • # of GLU determine the size of hydroPHOBIC inner cavity
    • of cup-shaped molecules
  • Solubilize drug molecules by binding in their hydrophobic cavity
    • Nontoxic & metabolize similarly to starch
  • ENHANCE drug conc. close to the membrane
    • Do NOT cross biological membranes (large MW & Polarity), drug does
  • ​Also used as recognition devices & scaffolds for artificial receptors
41
Q

Cyclodextrin (CD)

Pharmaceutical Applications

A
  • Enhance F & Stability
  • Stabilize flavors
  • Also used as recognition devices & scaffolds for artificial receptors
  • Convert Liquids/Oils –> free flowing powders
  • Prevent Admixture incompatibilites
  • REDUCE:
    • Odors / taste
    • Hemolysis / Evaporation
  • _​_Examples of drug CD complexes
    • Iodine, nicotine, nitroglycerin, OMEPRAZOLE, dexmethasone
    • indomethacin, HC, mitomycin
42
Q

Monosaccharides

A

AKA Simple Sugars

”-OSES”

  • Gluc-ose / Galact-ose / Rib-ose
  • 99% are straight chain compounds
  • D-glyceraldehyde is the simplest of the aldoses
  • Classified by presnce of ALDEHYDE or KETONE group
    • PLUS the number of Carbons
  • ​Most have D-Configuration
    • -OH group is on the right
    • DOES NOT MEAN THEY ARE ALL DEXTRO
43
Q

Monosaccharides:

# of Stereoisomers

A

2n = “n” is the number of stereocenters

aldotetroses = 2 (21)

pentoses = 4 (22)

hexoses = 8 (23)

think subtract 3 carbons from total carbons = n

44
Q

Hexose (hexosamine) Hemiacetals

Structures

A

Glu = ALL EQUITORIAL

Man = 2-axial

GAL = 4-AXIAL

45
Q

D-Glucose Cyclization

Hexofuranose

A
  • Pyranose form
    • ​more stable and more sweet
  • Furanose form (5-membered ring)
    • ​less stable, formed when heated up
46
Q

D-Ribose Cyclization

Pentopyronose

A
  • Pyranose
    • ​more stable
  • Furanose Form (5 membered ring)
    • ​functional riboses are mainly in this form
    • less stable, due to steric repulsion / eclipsing
47
Q

Raffinose

A
  • Reducing sugar
    • ​There is no reducing END in the structure (end is linked)
      • = full acetal structure
      • typically seen in most other oligosaccharides
  • There is no presence of a hemiacetal function
  • Similar to trehalose (anomeric to anomeric)
48
Q

Strong Acid –> Sugar

A
  • Monosaccharides are DEHYDRATED by strong acids
  • D-Ribose + Heat + HCL = Furfural (THF)
    • 5-hydroxymethyl furfural
      • basis for MOLISCH TEST
      • Test that detects carbohydrates
49
Q

Strong Base on Sugars

A
  • Sugars = weak acids
    • form SALTS @ HIGH pH (very basic)
    • –> 1,2-Enediol Salt is formed
  • Allows for interconversion of:
    • D-mannose / D-Fructose / D-glucose
50
Q

Reducing Sugars

A
  • Sugars that are susceptible to oxidation when heated
    • in the presence of an oxidizing agent (copper sulfate)
  • ALL MONOSACCHRIDES are reducing sugars
    • Raffinose is also a reducing sugar
51
Q

Glucose Measurement Methods

A
  • Three enzyme systems used to measure glucose:
    • Glucose Oxidase
      • ​produces h2o2
      • reacts w/ o-dianisidine –> pink color
      • –> D-gluconic acid = aldonic acid (pink)
    • Glucose Dehydrogenase
    • Hexokinase
52
Q

Amino Sugar

(special type of monosaccharide)

A

Contain an Amino group @ 2-position

  • ex. glucosamine, galactosamine, mannosamine
  • Sialic Acid = N-acetylneuraminic acid
    • 9carbon aminosurgar
    • constituant of bacterial peptidoglycan
      • important cell-wall component
  • ALL are constituents of mamalian mucous membranes and tissues
53
Q

Deoxysugar

A

Monosaccharides that lack 1+ hydroxyl groups

  • DNA, backbone = 2’deoxyribose
  • L-rhamnose = fermatative reacgent in bacteriology
  • L-fucose
  • ALMOST THE ONLY L-SUGARS in nature
  • 2’3’dideoxyribose
    • = DNA polymerase chain TERMINATORS
54
Q

Mutarotation

A

Change from Alpha to Beta

  • Occurs do to acid-catalyzed reversible hemiacetal-aldehyde equilibrium
    • ​starts w/ protonation of OR oxygen of hemiacital
      *
55
Q

Cyclitols

Inositols

A
  • Compounds w/ general formula C6H12O6
    • identical to hexoses but diff chemical properties
    • do not have aldehyde (hemiacetal) group
  • Suitable as a scaffold for proteins or membranes
  • useful as signaling molecules
  • not useful for energy storage
    • ​due to difficult metabolism
56
Q

Disaccharides

A

Codensation (release water) of 2 monosaccharides

simultaneous dehydration

hemiacetal + alcohol –> acetal

  • Most are still Reducing sugars
    • have a reducing end on the aglycone
  • Examples:
    • Sucrose
    • Lactose
    • Maltose
    • cellobiose
    • trehalose
57
Q

Sucrose

beta-fructose (cis relationship)

A
  • disaccharade that hydrolyzes to:
    • Glucose + Fructose (inverted sugar)
  • known as table sugar
    • from sugar cane/sugar beat
  • used to make syrups (viscous)
  • NON-REDUCING SUGAR
    • does not have reducing end on aglycone
58
Q

Lactose

beta-galactose - alpha-glucos

A
  • disaccharide hydrolyzes to:
    • glucose + galactose
  • ​Milk contains alpha/beta isomers in 2:3 ratio
  • used in infant formulation
  • LACTAID
59
Q

Maltose

A
  • maltose hydrolyzes to:
    • 2 molecules of glucose
    • (similar to cellobiose & trehalose)
  • aka malt sugar
    • germinating of barley grain
  • used as a nutrient
    • ovaltine, sweetener
    • substrate in fermenting liquor
60
Q

Fehling’s Test

A
  • differentiate between water soluble carbohydrate and ketone functional groups,
  • A test for reducing sugars and non-reducing sugar
  • Fehling’s Solution = Strong base
    • KOH / NaOH / CuSO4
      • ​oxidazing agent
    • catalyzes the ketose-aldose isomeration
    • –> POSITIVE TEST FOR KETOSES & all other monosaccharides

MedChem Midterm 3 (7 decks)

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