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1 - SOD > Phytochemistry > Flashcards

Phytochemistry Flashcards

1
Q

What is phytochemistry?

A

isolation and identification of compounds from plants

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2
Q

What is pharmacognosy and ethnopharmacognosy?

A

scientific basis for the use of plants in pharmacy

historical medicinal use of plans by different societies around the world

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3
Q

What is the difference between primary metabolism and secondary metabolism?

A

primary metabolism is the production of molecules common across many forms of life - carbohydrates, proteins

secondary metabolism is the production of compounds which are unique to a certain species of an organism - can be used for a number of different reasons

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4
Q

How can plants be transformed to give medicines?

A

plants can be transformed to give herbal medicines or a pure single compound

these can be used as drugs or be chemically modified to give drugs

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5
Q

What are the areas of the plant where the most useful natural products are found?

A 
aerial parts 
leaf 
flower 
fruit
bark
root
rhizone
bulb
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6
Q

What products can be extracted directly from the plant?

A

resin
gum
oils

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7
Q

How can compounds be extracted from plants?

A

1 - identify the plant
2 - dry the whole plant or the selected organ
3 - material containing the desired compound is crushed or finely chopped
- to increase surface area for extraction
4 - a solvent is used to extract the compound
= hot solvent is used with a soxhlet apparatus or supercritical carbon dioxide is used
5 - initial product results in a crude extract
= mixture of similar compounds
6 - crude extract goes through further extraction to get isolated product
= primarily chromatography, acid/base extraction
7 - compound is identified by spectroscopic methods
= NMR, UV, IR, MS or analytical chromatography (TLC, HPLC, GLC)

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8
Q

Why is supercritical carbon dioxide increasingly being used as a solvent for drug extraction from plants?

A

environmentally friendly
= can be boiled off at the end, no need to dispose of toxic chemicals

easily removed from extract
= heat to room temperature and it evaporates off

non-reactive
= does not interfere with the extract

extraction conditions can be changed to suit your needs
= temperature and pressure can be changed to selectively extract compounds of different polarities

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9
Q

What is a disadvantage of using hot solvent as an extraction method in plants?

A

leaves behind large quantities of organic solvent that need to be disposed of

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10
Q

What is a major constituent of the initial crude plant extract?

A

crude extract - initial extract of plant material hat gives a mixture of related/similar compounds

fatty acids

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11
Q

What is the structure of a fatty acid and how is it referred to as?

A

fatty acids are referred to as fixed oils (if liquid) or fats (if solid)

often found as esters
- R groups attached to an OOR’ group = especially as glycerides

structure is a hydrocarbon chain attached to a carboxylic acid group

  • the hydrocarbon chain can be saturated (no double bonds) or unsaturated (at least one double bond)
  • double bonds tend to be cis (same side)
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12
Q

What is the difference between glycerol and glyceride?

A

glycerol is a triol - an alcohol with three hydroxyl groups

glyceride is formed after a reaction between fatty acids and glycerol

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13
Q

How are soaps formed?

A

reacting fatty acid or their glycerides with a strong base (example - sodium hydroxide)

give the sodium salts of fatty acids
R group attached to OONa (charged O and Na)

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14
Q

What are waxes and how are they formed?

A

esters of fatty acids with long chain alcohols
- formed from a reaction between a fatty acid (hydrocarbon chain + carboxylic acid group) and a long chain alcohol (long hydrocarbon chain with a hydroxyl group)

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15
Q

What are volatile oils?

A

have a lower boiling point than fixed oils (fatty acids in liquid form)

can be isolated by steam distillation

tend to have two forms phenyl propenes or monoterpenes

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16
Q

What are volatile oils used for?

A

antibacterial use
therapeutic flavour
perfume properties

17
Q

What are monoterpenes?

A

major constituent of volatile oils
shows the chemical variety that can occur in different species with the same starting material
- monoterpenes are the starting materials for a whole range of terpene compounds

all have 10 carbon atoms in their structures

18
Q

How are monoterpenes formed?

A

synthesised from two 5-carbon units related to isoprene
- dimethylallyl pyrophosphate = DMAPP
- isopentyl pyrophosphate = IPP
these 5 carbon units react to give the 10 carbon monoterpenes

19
Q

What is an example of a monoterpene and how is it formed?

A

geranyl PP (10C)

  • formed from reacting DMAPP (5C) and IPP (5C)
  • is the common intermediate in monoterpene synthesis
20
Q

How can geranyl PP react further?

A

monoterpene common intermediate

- can react further to give linear compounds of cyclic compounds

21
Q

What are sesquiterpenes?

A

15 carbon compounds

can be cyclic or acyclic (linear) compounds

22
Q

How are sesquiterpenes formed?

A

synthesised from a monoterpene (10C) reacting with another molecule of IPP (5 carbon) to form a 15C compound

23
Q

What is an example of a sesquiterpene and how is it formed?

A

farensyl PP (15C)

  • formed as geranyl PP (10C) reacts with IPP (5C)
  • is the common intermediate

example

  • artemisinin can be used as a treatment for malaria
  • parthenolide can be as an anti migraine/headache
24
Q

What are diterpenes?

A

20 carbon compounds

  • intermediate from which other diterpenes are formed
  • many have a cyclic structure but can be linear
25
Q

How are diterpenes formed?

A

synthesised from a sesquiterpene reacting with another molecule of IPP (5 carbon)

26
Q

What is an example of a diterpene and how is it formed?

A

geranylgeranyl PP (20C)

  • formed as farensyl PP (15) reacts with IPP (5C)
  • is a common intermediate

example
- taxanes (Taxol) have potent anticancer activity

27
Q

What are triterpenes?

A

30 carbon compounds

- incldues steroids

28
Q

How are triterpenes formed?

A

synthesised from 2 sesquiterpenes (15C) reacting together

- farensyl PP reacts with farensyl PP

29
Q

What is an example of a triterpene and how is it formed?

A

squalene

  • formed as two molecules of farensyl PP (15C) react together
  • join with the two OPP reacting to form a bond = final product does not have OPP

reaction is catalysed by the enzyme squalene synthase

30
Q

How is squalene involved in steroid synthesis?

A

squalene can be epoxidised
- cyclic ether ring = 2C bonded with O
squalene epoxide cyclises to give the common intermediate for steroid synthesis
= has 4 rings

31
Q

What is tetraterpene?

A

40 carbon compound

- family of compounds includes carotenes/carotenoids and lycopene

32
Q

What is an example of a tetraterpene and how is it formed?

A

lycopene

  • formed as two molecules of geranylgeranyl PP (20C) react
  • react at the OPP end so end product does not have OPP
33
Q

What are features of tetratepenes?

A

compounds are highly coloured due to their conjugation
- form part of the distinctive pigmentation in flowers, tomatoes and carrots

conjugation means that

  • strongly absorb UV light so can protect itself from effects
  • are strong antioxidants
34
Q

What are alkaloids?

A

low molecular weight nitrogen containing compounds

  • found mainly in plants
  • generally basic
  • wide range of biological activity
35
Q

What are examples of alkaloids?

A

belladonna

  • 0.3 - 0.6% alkaloid contained
  • highly poisonous
  • mixed alkaloid extract can be used as GI sedative and roots can be used for external pain relief (plasters)

coca

  • 0.7 - 2.5% alkaloid but 40 - 50% cocaine
  • cocaine = local anaesthetic
  • combats fatigue, hunger and cold
36
Q

What are stilbenes and flavonoids?

A

are both alkaloids

stilebenes

  • resveratol = potent antioxidant from wine and red grape
  • combretastatin = potent cytotoxic (anticancer compound) from bush willow, inhibits tubular formation

flavonoids
- brightly coloured antioxidants from brightly coloured parts of plants
isoflavonoids
- act as phyto-oestrogens

37
Q

How can biosynthetic routes be established?

A

to find the origin of the biological molecule which are generally formed from two or three carbon fragments

  • isotopes are used
  • plants can be fed with a labelled acetate group
  • analytical techniques can be used to find where the isotope has been incorporated into the compound
38
Q

How do analytical techniques show the biosynthetic process?

A

shows whether the isotope (acetate molecule) has been

  • used as a building block
  • how many of the acetate molecules have been used
  • how the acetate groups are linked

can show the full process if the studies are repeated with different intermediates labelled at different points

1 - SOD (27 decks)

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