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AAI > Chemistry > Flashcards

Chemistry Flashcards

1
Q

Adrenaline

A

chiral molecule
hormone & neurotransmitter
controls: heart rate, blood vessel diameters, air passage diameter, metabolism

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2
Q

Adrenaline chemical structure

A

phenyl group with 2 hydoxyls, alkyl side chain with a hydroxyl group terminated with a secondary amine

mono-amine, family: catecholamine

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3
Q

Catecholamine

A

1,2-dihydroxybenzene

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4
Q

Adrenaline as a drug

A

agonist, treatment for anaphylaxis
reason: very fast treatment

Auvi-Q, epipen

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5
Q

Noradrenaline

A

replace N-mthyel with N-H

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6
Q

Potency

A

Adrenaline: same for alpha and beta

NA: greater potency for alpha

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7
Q

Adrenaline Biosynthesis

A
  1. L-Tyrosine (from food) + Tyrosine hydroxylase –> Levodopa (treating Parkinson’s)
  2. Levodopa + Dopa decarboxylase –> Dopamine (pleasure sensation in the brain)
  3. Dopamine + Dopamine β-hydroxylase –> Noradrenaline
  4. Noradrenaline + N-methyltransferase –> Adrenaline
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8
Q

Adrenoceptors types

A

β1: increase heart rate, renin secretion from kidneys

β2 receptors: relax bronchi, stimulate insulin release, inhibit histamine release from mast cells

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9
Q

Isoetharine

A

3rd generation
ultra-short acting

β2 selectivity obtained by:

  1. introducing alkyl substituents to the side chain linking aromatic ring and amine group
  2. varying the alkyl substituents on the N atom

Ultra-short acting (<3 hrs) due to:
Taken up by tissues and mutilated by the enzyme catechol-O-methyl-transferase (COMT) to form an inactive metabolite

Fix:
Replaced meta-OH with -CH2OH –> more resistant to metabolism

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10
Q

Isoprenaline non-specificity

A

Isoprenaline, acts on β1 (heart) & β2 (bronchi) –> mortality epidemic

Discovered when small doses given to hypoxemic dogs. Hypoxemia is common is asthmatic patients.

Salbutamol is 7 times less potent in raising heart rate in humans

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11
Q

Isoprenaline non-specificity

A

Isoprenaline, acts on β1 (heart) & β2 (bronchi) –> mortality epidemic

Discovered when small doses given to hypoxemic dogs. Hypoxemia is common is asthmatic patients.

Salbutamol is 7 times less potent in raising heart rate in humans

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12
Q

Fenoterol

A

short-acting β2 agonist
can activate β1 receptors at doses higher than recommended
withdrawn from NZ due to mortality issues thought to be due to excessive usage for severe asthma attacks in absence of medical assistance, up to 80 puffs before seeking medical attention

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13
Q

Adrenoreceptors SAR

A

Important features:

  • configuration at stereocentre where only R stereoisomer most effective
  • Bigger R group at amine group favours β selectivity over α
  • R group plays role in β2 selectivity and duration of action
  • meta OH at phenyl ring causes bioavailability issues due to metabolism by COMT, largely fixed when replaced by -CH2OH
  • para phenolyc hydroxyl group plays a role in β vs α selectivity. Removal of the hydroxyl causes the molecule to favour α receptors. over β receptors
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14
Q

Salbutamol

A

short-acting (4-6 hours)

same potency as isoprenaline but less active on the heart

meta-CH2OH group –> longer duration and more resistant to metabolism by COMT

bulky tert-butyl group at amine:

  • reach and form additional interactions wiht non-polar region in the binding site
  • produces selectivity for β2 receptors
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15
Q

salbutamol enantiomers

A

R enantiomer is more active but marketed it as a racemate becuase S blocks the metobolism of R

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16
Q

Salmeterol

A

treatment of nocturnal asthma (arnd 4 am)

increased length of the N-alkyl substituent with a hydrocarbon chain and aromatic ring:

-increased lipophilicity to bind more strongly to tissue in the vicinity of the adrenoreceptors –> longer duration of action (2x longer than salbutamol, 12 hours)

R enantiomer more active
meta-CH2OH –> higher bioavailabilty
bulky R-group: β2 selectivity & higher lipophilicity

17
Q

Salmeterol vs Salbutamol

A

slower onset of action due to:
initially diffuse into plasma membrane of lung cells and
slow release back outside the cell to receptors –> suitable for prevention rather than relief of asthma attacks

-longer duration of action due to:
accumulate in plasma membrane then release over time to receptors–> nocturnal asthma

18
Q

SAR

A

Structure-Activity Relationship

19
Q

Steroids structure

A
  • Based on ‘gonane’ nucleus
  • 19/20 carbons
  • 4 fused rings: 3 6-membered, 1 5-membered
  • 2 methyl group at C-10 and C-13 (A-B junction and C-D junction)
  • alcohol side chain at C-17
  • most naturally occuring steroids: 5-alpha gonane /5-beta gonane types –> referring to orientation of hydrogen atom at C-5
20
Q

Steroids in humans

A
  • sex hormones (testosterone, estrogen, progesterone
  • cholesterol: essential component in cell membranes to establish permeability and fluidity of cell membranes
  • corticosteroids: steroid hormones that are not sex hormones, can be classifed as:
    glucocorticoids: metabolism, stress response, immune response and inflammation, present in almost in every mammal cell

mineralocorticoids: renal and blood function, water and electrolyte balance

21
Q

Steroids as meds

A
  • arthritis
  • contraception
  • asthma
  • anabolic steroids for strength building (often illicit)
22
Q

Cortisone

A

21 carbon glucocorticoid

released in reaction to stress

released with adrenaline and elevate blood pressure to prep for fight or flight response

23
Q

Cortisone as a med

A
  • suppress immune system (immune diseases and organ transplants)
  • anti-inflammatory (arthritis)
  • increase blood sugar (care with diabetes)
24
Q

Corticosteroids and arthritis

A
  • cortisone
  • prednisone
  • methylprednisolone
  • systemically or direct injection into joint
  • often a particulate suspension –> can re-crystallise in join after injection –> inflammation in the surrounding tissue and pain worse than before the shot
25
Q

Steroids and asthma

A
  • reduce inflammation within bronchio tubes

- inhaled as aerosol/spray or taken orally as tablets (ex: prednisone), vein injections for severe symptoms

26
Q

Steroids stereochemistry

A
  • badge (thick bond/above ring) –> denoted as β
  • dotted bond (below ring/into page) –> denoted as α

-naturally occurring steroids: all 4 rings in chair formation

  • B-C ring junction tans
  • C-D ring junction almost always trans

-A-B ring junction can be trans or cis:
trans –> H at C-5 is α oriented –> colestanes

cis –> H at C-5 is β oriented –> coprostanes

  • stereochemically rigid (cannot change conformation without breaking bonds)
27
Q

Physical properties of steroids

A
  • stable compounds
  • white crystalline solids
  • mp 100-250 c
  • poorly soluble in water, ok in ethanol and organic solvents (due to high hydrocarbon percentage)
28
Q

Cholestrol

A

sterol: hydroxyl group at C-3
- precurosr for all steroid hormones, bile acids and vit D
- 30-50g cholestrol in human body
- 37 steps of biosynthesis

29
Q

Cholestrol –> Pregnenolone

A
  1. Cholestrol oxidised into dihydroxylated intermediate
  2. intermediate undergoes oxidative cleavage to form pregnenolone with ketone side chain
  3. isocarproic acid as side product
30
Q

Pregnenolone –> other steroids

A
  1. oxidation of C-3 hydroxyl group to a ketone function
  2. β - γ and saturated ketone function will undergo 2-step enzymatic catalysed isomerisation to give α - β unsaturated system in progesterone
31
Q

Keto-enol tautomerisation

A

acid-catalysed tautomerisation

base-catalysed

AAI (13 decks)

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