Drug Sources

Until the end of the 19th century, medicines
were natural organic or inorganic
products, mostly dried, but also fresh,
plants or plant parts. These might contain
substances possessing healing
(therapeutic) properties or substances
exerting a toxic effect.
In order to secure a supply of medically
useful products not merely at the
time of harvest but year-round, plants
were preserved by drying or soaking
them in vegetable oils or alcohol. Drying
the plant or a vegetable or animal product
yielded a drug (from French
“drogue” – dried herb). Colloquially, this
term nowadays often refers to chemical
substances with high potential for physical
dependence and abuse. Used scientifically,
this term implies nothing about
the quality of action, if any. In its original,
wider sense, drug could refer equally
well to the dried leaves of peppermint,
dried lime blossoms, dried flowers
and leaves of the female cannabis plant
(hashish, marijuana), or the dried milky
exudate obtained by slashing the unripe
seed capsules of Papaver somniferum
(raw opium). Nowadays, the term is applied
quite generally to a chemical substance
that is used for pharmacotherapy.
Soaking plants parts in alcohol
(ethanol) creates a tincture. In this process,
pharmacologically active constituents
of the plant are extracted by the alcohol.
Tinctures do not contain the complete
spectrum of substances that exist
in the plant or crude drug, only those
that are soluble in alcohol. In the case of
opium tincture, these ingredients are
alkaloids (i.e., basic substances of plant
origin) including: morphine, codeine,
narcotine = noscapine, papaverine, narceine,
and others.
Using a natural product or extract
to treat a disease thus usually entails the
administration of a number of substances
possibly possessing very different activities.
Moreover, the dose of an individual
constituent contained within a
given amount of the natural product is
subject to large variations, depending


upon the product‘s geographical origin
(biotope), time of harvesting, or conditions
and length of storage. For the same
reasons, the relative proportion of individual
constituents may vary considerably.
Starting with the extraction of
morphine from opium in 1804 by F. W.
Sertürner (1783–1841), the active principles
of many other natural products
were subsequently isolated in chemically
pure form by pharmaceutical laboratories.
The aims of isolating active principles
are:
1. Identification of the active ingredient(
s).
2. Analysis of the biological effects
(pharmacodynamics) of individual ingredients
and of their fate in the body
(pharmacokinetics).
3. Ensuring a precise and constant dosage
in the therapeutic use of chemically
pure constituents.
4. The possibility of chemical synthesis,
which would afford independence from
limited natural supplies and create conditions
for the analysis of structure-activity
relationships.
Finally, derivatives of the original constituent
may be synthesized in an effort
to optimize pharmacological properties.
Thus, derivatives of the original constituent
with improved therapeutic usefulness
may be developed.