Plant Alkaloids Flashcards
alkaloids end in
“INE”
Alkaloids are: (5 things)
- 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
there are 3 groups of alkaloids
- true alkaloids
- Protoalkaloids
- Pseudoalkaloids
True alkaloids include these 3 drugs
morphine, atropine, codeine
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
True alkaloids
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
Protoalkaloids
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
pseudoalkaloids
where are alkaloids commonly found in plants
- roots and shoot apices
- epidermal and hypodermal cells
what are some families of plants that are rich in alkaloids
- papervaceae
- solanaceae
- apocynaceae
- rubiaceae
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
- True and Pseudo alkaloids
- Protoalkaloid - sidechain
what is introconversion and how does it relate to the basicity of alkaloids
- 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
what forms the basis of extraction and purification of alkaloids
introconversion and relative solublities in immiscible solvents
are alkaloids soluble, insoluble or practically insoluble in water and organic solvents
- practically insoluble in water
- soluble in organic solvents
what are the solubility exceptions for:
- morphine and caffeine
- morphine and phenolic alkaloids
- colchicine
- caffeine
- ergometrine
- insoluble in ether
- soluble in aqueous caustic alkali solution
- soluble in cold water
- soluble in hot water
- more soluble in water than other ergots
alkali salts are soluble in what and insoluble in what
- soluble in water and alcohol
- insoluble in organic soludions
how can alkaloids be precipitated from neutral or slightly acidic solutions using
- halogens
- heavy metal salts
- complex O2 acid reagents
which reagents are used to detect the presence of alkaloids in extracted crude drugs
- Mayers reagent
- Dragendorff reagent (solenaceous)
- Wagner Reagent (emetine)
what are important points to consider when using precipitating agents
- 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
what colour is the ppte for alkaloids
beige, orange or brown
what is a way to avoid false positives in testing of alkaloids using reagents
use multiple reagents
in addition to colorimetric analysis mayers reagent, dragendorf reagent and wagner reagent can be used in
TLC
what is a common name for solanaceous plants
night shades
solanaceous plants are heat stable or labile
labile
what three degradative processes are alkaloids subject to?
As a result alkaloids should be stored in
- oxidation
- hydrolysis
- photo-degradation
- well sealed container which is protected from light
extraction of alkaloids involves (3)
- 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
individual alkaloids may be separted using the following 7 methods
- selective solubility in solvents of varying polarity
- ion exchange resin
- counter current chromatography
- gradient pH extraction
- column chromatography
- thick layer chromatography
- preparative HPLC
alkaloid assays include (3)
- volumetric determination
- absorbimetric determination
- chromatographic determination
the volumetric determination of alkaloids is based upon
- 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
Absorbimetric assays are used when alkaloids are
chemically similar and absorb in the UV range
the major pharmaceutical groups of alkaloids include these 5 groups
- pyridine/piperiddine alkaloids
- tropane alkaloids
- quinoline alkaloids
- isoqunoline alkaloids
- indole alkaloids
pyridine/piperidine alkaloids include
Nicotine
tropane alkaloids are further broken down into these two groups
- solanaceous tropane alkaloids (atropine, hyoscine)
- Erythroxylaceae tropane alkaloids (Cocaine)
cinchona alkaloids are part of this group which includes this drug
quinoline alkaolids
quinine and quinidine
isoquinoline alkaloids include these 3 groups. include an example for each group
- Curare alkaloid - arrow poison
- ipecacuanha - ipacac
- opium alkaloids - morphine/codeine
this group of alkaloids is derived from tryptophan or tryp + mevalonic acid and include the following sub-groups
- physostigma
- strychnos
- ergot alkaloids
- rauwolfia
- periwinkle
indole alkaloids
for each of these indole alkaloids provide an example of a drug
- physostigma
- strychnos
- ergot alkaloids
- rauwolfia
- periwinkle
- physostigma - physostigmine
- strychnos - strichnine, calabash curare
- ergot alkaloids - ergot; lysergic acid derivatives (LSD), ergotamine, ergometrine
- rauwolfia
- periwinkle
- vinca alkaloids - vinblastine
- vincristine
