Pharmacognosy

Question 1

What is pharmacognosy?

Answer 1

is the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drug substances of natural origins as well as the search for new drugs from natural sources

Question 2

What are the advantages and disadvantages of using natural products as drugs?

Answer 2

advantages

• greater complexity
• single enantiomers isolated
• huge biodiversity available

disadvantages

• can be very difficult and costly to synthesise
• or may be available only in limited amounts from a rare natural resource

Question 3

What are the four methods used to find natural products?

Answer 3

ethnomedicinal approach
- looks at what traditional healers are using to treat the disease and studies that plant/s
= validate the use

ecological approach
- looks at the various aspects of animal behaviour, eating patterns as well as plant defence mechanisms

metabolomics
- looks at the global metabolite profile of an extract

computational methods

• reverse pharmacognosy
• ligand docking
• in silica screening

Question 4

What are the different classes of drug used to treat malaria?

Answer 4

quinine = from the chinchona tree
- is an alkaloid, basic amine
- is anti-pyretic, anti-inflammatory, analgesic and anti-malarial
= currently used as a treatment rather than a prophylactic

chloroquine - synthetic analogue of quinine
= most commonly used

artemisinin
- is effective against chloroquine resistant strains/resistant strains of Plasmodium falciparum
- analogues can be prepared by studying the structure activity relationship
= analogues can be more active than artemisinin

Question 5

What does the activity difference between artemisinin and its analogues show?

Answer 5

artemisinin is less active than dihydroartemisinin/artemether/sodium artesunate
- shows that the lactone carbonyl in artemisinin is not crucial

artemisinin is more active than deoxyartemisinin
- shows that the endoperoxide link is important

Question 6

What is the mechanism of action of artemisinin?

Answer 6

parasite infects the RBCs of the host cell
- causes release of iron from the heme

ferrous ions reduce the endoperoxide ring of artemisinin to form radicals which kills the parasite by oxidising vital biomolecules
- parasite is implicit in its own death as it causes the release of iron

Question 7

What are the different drugs used to treat cancer?

Answer 7

camptothecins
- is a cytotoxic alkaloid = anti-cancer

• is a topoisomerase I inhibitor
  = shows selectivity for cancer cells that have a higher level
• structure shows that the lactone carbonyl is essential for activity but is not water soluble and is toxic
  = semi-synthetic analogues can be made which have an added alcohol or amine group to aid solubility

Question 8

What are the different classes of drug that inhibit tubulin polymerisation?

Answer 8

treats cancer

vinca alkaloids
- vincristine, vinblastine, vindesine

spongistatin I

podophyllotoxins

cryptophycins

combretastatins

dolostatin
cephalostatin

Question 9

What are the types of plant glycosides? What can they be used for?

Answer 9

a glycoside consists of an aglycone and a sugar unit
- have a very small range between therapeutic and toxic
cardenolides
- digitoxigenin

bufadienolides
- hellabrigenin

Question 10

What are the different classes of drug that inhibit tubulin depolymerisation?

Answer 10

paclitaxol

- treats cancer

Question 11

What is Bryostation used for?

Answer 11

boosts the immune system of cancer patients

- would be given together with other chemotherapeutic agents