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Pharmacognosy & Pharmaceutical Biology > Plant Alkaloids > Flashcards

Plant Alkaloids Flashcards

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1
Q

alkaloids end in

A

“INE”

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2
Q

Alkaloids are: (5 things)

A
  • Basic (alkali - like)
  • contain ‘N’ in a ring or side chain
  • found in plants and animals
  • complex chemical structures
  • physiologically active in animals and man
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3
Q

there are 3 groups of alkaloids

A
  • true alkaloids
  • Protoalkaloids
  • Pseudoalkaloids
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4
Q

True alkaloids include these 3 drugs

A

morphine, atropine, codeine

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5
Q

which group of alkaloids (true, pseudo or proto alkaloids have these features:

  • are basic
  • contain heterocyclic Nitrogen
  • synthesized from amino acids, especially tyrosine, phenylalanine, tryptophan, histidine
  • have limited distribution in plant kingdom
  • are toxic substances acting on the CNS
A

True alkaloids

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6
Q

which group of alkaloids (true, pseudo or proto alkaloids have these features:

  • Nitrogen is in a side chain
  • are derivatives of amino acids
  • include ephedrine, colchicine, paclitaxel
A

Protoalkaloids

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7
Q

which group of alkaloids (true, pseudo or proto alkaloids have these features:

  • are not derived from aminoacids
  • structurally based on Terpenes, Steroids, Nicotinic Acid and Purines
  • include Caffeine and theobromine
A

pseudoalkaloids

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8
Q

where are alkaloids commonly found in plants

A
  • roots and shoot apices
  • epidermal and hypodermal cells
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9
Q

what are some families of plants that are rich in alkaloids

A
  • papervaceae
  • solanaceae
  • apocynaceae
  • rubiaceae
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10
Q

which of the three types of alkaloids have at lease one nitrogen in a heterocyclic ring.

Name the third group and where the Nitrogen is contained

A
  • True and Pseudo alkaloids
  • Protoalkaloid - sidechain
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11
Q

what is introconversion and how does it relate to the basicity of alkaloids

A
  • introconversion is when the compound easily forms salts with the addition of acid, and will convert back to the basic form readily upon addition of base
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12
Q

what forms the basis of extraction and purification of alkaloids

A

introconversion and relative solublities in immiscible solvents

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13
Q

are alkaloids soluble, insoluble or practically insoluble in water and organic solvents

A
  • practically insoluble in water
  • soluble in organic solvents
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14
Q

what are the solubility exceptions for:

  • morphine and caffeine
  • morphine and phenolic alkaloids
  • colchicine
  • caffeine
  • ergometrine
A
  • insoluble in ether
  • soluble in aqueous caustic alkali solution
  • soluble in cold water
  • soluble in hot water
  • more soluble in water than other ergots
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15
Q

alkali salts are soluble in what and insoluble in what

A
  • soluble in water and alcohol
  • insoluble in organic soludions
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16
Q

how can alkaloids be precipitated from neutral or slightly acidic solutions using

A
  • halogens
  • heavy metal salts
  • complex O2 acid reagents
17
Q

which reagents are used to detect the presence of alkaloids in extracted crude drugs

A
  • Mayers reagent
  • Dragendorff reagent (solenaceous)
  • Wagner Reagent (emetine)
18
Q

what are important points to consider when using precipitating agents

A
  • different reagents have diff sensitivities to alkaloids
  • if the solution contains plant constituents it could yield a false positive
  • protoalkaloids, quat alkaloids and amine oxides do not PPTE
19
Q

what colour is the ppte for alkaloids

A

beige, orange or brown

20
Q

what is a way to avoid false positives in testing of alkaloids using reagents

A

use multiple reagents

21
Q

in addition to colorimetric analysis mayers reagent, dragendorf reagent and wagner reagent can be used in

A

TLC

22
Q

what is a common name for solanaceous plants

A

night shades

23
Q

solanaceous plants are heat stable or labile

A

labile

24
Q

what three degradative processes are alkaloids subject to?

As a result alkaloids should be stored in

A
  • oxidation
  • hydrolysis
  • photo-degradation
  • well sealed container which is protected from light
25
Q

extraction of alkaloids involves (3)

A
  • extraction of alkaloids using either ethanol for extraction followed by, partitioning with organic solvent and interconversion with a base, followed by drying
  • extraction of alkaloids by interconversion with a base and reflux in organic solvent followed by filtration and partitioning in aqueous acid to convert back to base followed by drying
  • cold extraction using percolation method. material is made basic to being with then after a number of hours and removal of the extracted solvent, made acidic and partitioned with organic solvent then dried
26
Q

individual alkaloids may be separted using the following 7 methods

A
  1. selective solubility in solvents of varying polarity
  2. ion exchange resin
  3. counter current chromatography
  4. gradient pH extraction
  5. column chromatography
  6. thick layer chromatography
  7. preparative HPLC
27
Q

alkaloid assays include (3)

A
  • volumetric determination
  • absorbimetric determination
  • chromatographic determination
28
Q

the volumetric determination of alkaloids is based upon

A
  • the fact that alkaloids are bases and comparable in strength to ammonia
  • methyl red is used as indicator for this titrimetric assay
  • extract is dried to remove solvent, then dissolved in acid and back titrated with alkali
29
Q

Absorbimetric assays are used when alkaloids are

A

chemically similar and absorb in the UV range

30
Q

the major pharmaceutical groups of alkaloids include these 5 groups

A
  1. pyridine/piperiddine alkaloids
  2. tropane alkaloids
  3. quinoline alkaloids
  4. isoqunoline alkaloids
  5. indole alkaloids
31
Q

pyridine/piperidine alkaloids include

A

Nicotine

32
Q

tropane alkaloids are further broken down into these two groups

A
  • solanaceous tropane alkaloids (atropine, hyoscine)
  • Erythroxylaceae tropane alkaloids (Cocaine)
33
Q

cinchona alkaloids are part of this group which includes this drug

A

quinoline alkaolids

quinine and quinidine

34
Q

isoquinoline alkaloids include these 3 groups. include an example for each group

A
  1. Curare alkaloid - arrow poison
  2. ipecacuanha - ipacac
  3. opium alkaloids - morphine/codeine
35
Q

this group of alkaloids is derived from tryptophan or tryp + mevalonic acid and include the following sub-groups

  • physostigma
  • strychnos
  • ergot alkaloids
  • rauwolfia
  • periwinkle
A

indole alkaloids

36
Q

for each of these indole alkaloids provide an example of a drug

  • physostigma
  • strychnos
  • ergot alkaloids
  • rauwolfia
  • periwinkle
A
  • physostigma - physostigmine
  • strychnos - strichnine, calabash curare
  • ergot alkaloids - ergot; lysergic acid derivatives (LSD), ergotamine, ergometrine
  • rauwolfia
  • periwinkle
    • vinca alkaloids - vinblastine
    • vincristine

Pharmacognosy & Pharmaceutical Biology (14 decks)

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