What’s in a medicine?
Storylines WM1: The
development of modern
ideas about medicines
Useful definitions

Pharmaceuticals
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Complex compounds
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Drugs
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Poison
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Pharmacology
Active ingredients of medicines
that alter the body’s chemistry.
A drug which is not beneficial to
the body.
The study of drugs.

Pharmacy

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The art and science of making
and dispensing medicines.
WM1 The development of modern
ideas about medicines.


1000s of years ago, medicines were used by
‘trial and error’; no-one knew how they
‘worked’.
Today, molecular pharmacologists design
drugs which have specific effects.
>>> activity WM1 The origins and
development of the modern pharmaceutical
industry.
WM2 Medicines from nature.
Modern pharmacy is based on herbal and
folk remedies. Remedies from “old wives’
tales” are investigated to find the active
ingredient.
 Doctrine of signatures: the idea that illnesses
can be cured by plants which are associated
with them.
Eg dock leaves for stinging nettle stings.

Medicines from willow bark
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Old ‘Doctrine of signatures’ idea: marshy
ground causes fevers. Willow trees grow
there – so use them as the remedy!
Hippocrates (400 BC) – willow leaf brew
eases pain of childbirth.
Edward Stone (1763) – willow bark reduces
fevers.
Culpeper’s Herbal
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Nicholas Culpeper (1616-1654) published his
astrological botany book ‘Herbal’ in 1640.
His decoction of ‘bruised leaves with pepper
in wine’ was most effective at: staunching the
bleeding of wounds; suppressing vomiting;
clearing acne.
Modern uses: salicin, found in the bark, is
used to make aspirin for treating malaria.
The salix drug

Salicin, named after salix (Latin for ‘Willow’),
has no pharmaceutical effect.

The body converts salicin to salicylic acid by
hydrolysis and then oxidation.
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>> Do activity WM2 and extract your own
salicylic acid!
WM3 Identifying the active chemical in
willow bark.
What’s the structure of salicylic acid?
These chemical tests give some clues:
1. The compound is weakly acidic in aqueous
solution.
2. Reactions with alcohols produce fruitysmelling ESTERS.
3. It turns a neutral solution of iron (III) chloride
an intense PINK.
What do these tests show?

Tests 1 and 2 are characteristic of
CARBOXYLIC ACIDS.
COOH
OH

Test 3 shows that PHENOL is present.