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PL2002 > Alkaloids > Flashcards

Alkaloids Flashcards

1
Q

What are alkaloids?

A

Products from secondary metabolism in plants

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2
Q

What are alkaloids used for in plants?

A

Bitter taste to defend against herbivores
A way to store N

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3
Q

Modern uses of alkaloids

A

Caffiene
Nicotine
Cocaine

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4
Q

Basic amine + acid ——> ?

A

Salt of weak base

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5
Q

What are most alkaloids soluble in?

A

organic solvents

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6
Q

What is the isolation and extraction process of alkaloids?

A

Power plant material
Extract with dilute acid
Wash with organic solvent
Neutralise with a base
Free base may need extracted with organic solvent

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7
Q

Ways to purify alkaloids?

A

Fractional Precipitation
Fractional Crystallisation
Steam Distillation
Sublimation
Column Chromatography

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8
Q

How does steam distillation purify alkaloids?

A

Volatile or low BP alkaloids are carried in steam
Alkaloids will separate from water as they are immiscible

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9
Q

How does sublimation purify alkaloids?

A

Solid phase to vapour phase
Cooling quickly to return to solid phase
Use cold-finger apparatus with vacuum
Material with does not sublime stay in test tube

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10
Q

How does chromatography purify alkaloids?

A

Separates alkaloids based according to polarity

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11
Q

Hager’s Reagent

A

Piric acid
Piccrates form
Yellow/orange colour

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12
Q

Mayer’s Reagent

A

Mercuric potassium iodide solution
White/yellow

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13
Q

Wagner’s Reagent

A

Potassium Iodide
Red/Brown precipitate

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14
Q

Dragendorff’s reagent

A

Potassium bismuth iodide spolution
Orange precipitate

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15
Q

What is transamination?

A

Substitution between amino group and ketone of neighbouring keto acid

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16
Q

What is decarboxylation?

A

Carboxylic acid on the amino acid is removed in the form of CO2

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17
Q

How are amino alkaloids different?

A

N is in amino group and not a member of a heterocyclic ring

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18
Q

How do ephedrine and pseudoephedrine differ?

A

Pseudoephedrine has different stereochemistry

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19
Q

What are the effects of ephedrine?

A

Increased BP
Vasoconstrictor
Appetite suppression

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20
Q

How many enantiomers are there for 2 chiral centres?

A

4

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21
Q

What type of alkaloid is methamphetamine?

A

Amino

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22
Q

How do beta blockers work?

A

cardioactive b-adrenoceptor blocking agents, control the rate and force of cardiac contractions in the management of hypertension

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23
Q

What are pyridine alkaloids derived from?

A

Nicotinic acid

24
Q

What are piperidine alkaloids derived from?

A

Lysine

25
Q

What are the effects of nicotine?

A

Hypertension in low doses
Toxic doses can cause respiratory depression

26
Q

What is the structure of tropane alkaloids?

A

Pyrrolidine and Piperidine rings that share N and 2C atoms

27
Q

How is cocaine synthesised?

A

Mixed ester extract from plants is hydrolysied to Ecogonine
Ecogonine is esterified, methylated and benzolyated to cocaine

28
Q

What is essential for anesthetic behaviour?

A

Aromatic carboxylic acid and basic amine group
Must be separated by a form of chain

29
Q

What is cocaine used in now?

A

Brompton’s cocktail with morphine

30
Q

Where is epibatidine found?

A

In poisonous frogs - 200-500x more potent than morphine

31
Q

What are quinoline alkaloids derived from?

A

Tryptophan

32
Q

What is the difference between quinoline and isoquinoline?

A

In isoquinoline, N is one position away from position in quinoline

33
Q

What form is the N usually in on isoquinoline alkaloids?

A

Quaternary salt form - influences solubility properties

34
Q

How is morphine biosynthesised?

A

From reticuline - single bonds rotate
Transition phase has 2 radicals

35
Q

Solubility of morphine

A

Morphine is organic compound and semi polar so does not dissolve well in water
Basic N will protonate in HCl to form quaternary salt - very soluble in aqueous acid

36
Q

Why is morphine soluble in aqueous base and acid but codeine only in aqueous acid?

A

Codeine has a MeO group masking OH group from morphine so will not react in aqueous base

37
Q

How is heroin synthesised?

A

Morphine + acetic anhydride —> diacetylmorphine
Esterification reaction

38
Q

How is heroin metabolised?

A

Heroin undergoes deacetylation in first pass metabolism so is a prodrug

39
Q

How does the ester group affect heroin?

A

Makes heroin more lipophilic so crosses the BBB when injected

40
Q

Why is codeine used instead of morphine?

A

Demethylated in the liver so has the same pain killing effect but with less euphoria

41
Q

What are the binding interactions with an opioid receptor?

A

Ionic bonding, Van der Walls (aromatic ring) and H-Bonding

42
Q

What are imidazole alkaloids synthesised from?

A

Histidine by decarboxylation

43
Q

What are the main actions of imidazole alkaloids?

A

Increases saliva
Decreases heart rate
Increases urination

44
Q

What is the structure of purine alkaloids?

A

Pyrimidine ring fused to an imidazole ring - lots of Ns

45
Q

What are common purine alkaloids derived from?

A

Xanthine structure

46
Q

What are common purine alkaloids?

A

Caffeine and theobromine

47
Q

What is the structure of indole alkaloids?

A

Benzene ring fused to a pyrolle ring

48
Q

Are indole alkaloids bases?

A

No because the N lone pair is in the π cloud of electrons

49
Q

What are indole alkaloids formed from?

A

Tryptophan amino acid

50
Q

What type of alkaloid is serotonin?

A

Indole

51
Q

What are ergot alkaloids based on?

A

Indole alkaloids with an extra chain than contains N

52
Q

What are medicinally useful ergot alkaloids?

A

LSD

53
Q

What does LSD do?

A

Mimics action of serotonin
Time distortion
Crawling geometric patterns

54
Q

What type of alkaloid is strychnine?

A

Indole/Ergot

55
Q
A

PL2002 (7 decks)

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