Observation of the properties of plants and animals can
help to guide a random search. For example, if certain types
of fruits remain fresh while others rot, we might expect the
former to contain antifungal agents. An example of this type
of collection is the gathering of tunicates (“sea squirts”)
and sponges in the Caribbean. The chemists harvest the
samples by diving from research vessels (see Fundamentals,
Fig. F.1). The samples are tested for antiviral and antitumor
activity in a chemical laboratory on the ship. The antiviral
drug didemnin-C and the anticancer drug bryostatin 1 were
discovered in marine organisms.
The guided route requires fewer samples for testing
because the chemist works with a native healer, the ancient
lore guiding the modern chemistry. Often an ethnobotanist,
BOX 4.1 FRONTIERS OF CHEMISTRY: DRUGS BY DESIGN AND DISCOVERY
A field biologist examines a plant in a South American rainforest.
The plant produces chemicals that will be investigated for their
medicinal value.
a specialist in plants used for native healing, joins the team.
This approach saves time for the scientists and can provide
an economic benefi t for the healers and their nations as
well. Drugs that have been discovered in this way include a
variety of anticancer and antimalarial drugs, blood-clotting
agents, antibiotics, and medicines for the heart and digestive
system.
Once the empirical and molecular formulas of the active
compounds are determined, then their structural formulas
are sought. At that point, synthetic work can begin. The
chemist can identify compounds in the material that have
medicinal value and fi nd a way to synthesize them, or prepare
them in the laboratory, so that they can be made available
in large quantities.