Fundamentals of Medicinal Chemistry

O O

H

H

CH 2 OH

O

H

OH

O

H

H

H

OCH 3

H

H OH

H

CH 3

H

OH

CH 3

OH

CH 3

OH

O

O

HO

Figure 2.1 The common foxglove and the structure of digitalis

cardiac stimulant digitalis from fox gloves (Figure 2.1) and the antidepressant

reserpine isolated fromRauwolfia serpentina.

Once screening identifies a material containing an active compound, the

problem becomes one of extraction, purification and assessment of the pharma-

cological activity. However, the isolation of useful quantities of a drug from its

land or sea sources can cause ecological problems. The promising anticancer

agent Taxol (Figure 2.2), for example, was originally isolated from the bark

of the Pacific yew tree. However, the production of large quantities of Taxol

from this source would result in the wholesale distruction of the tree, a state

of affairs that is ecologically unacceptable. It is vitally important that plant,

shrub, tree and marine sources of the world are protected from further erosion,

HO

CH 3

CH 3

CH 3

O

OH

CH 3

O

CH C

3

O

Ph

CH O

3

O

OPhO

PhCOO

N

HOH

Figure 2.2 Taxol, isolated from the bark of the Pacific yew

44 AN INTRODUCTION TO DRUGS AND THEIR ACTION