in their importance in drug design. Prostaglandins affect blood pressure, blood clotting,
gastric secretion, kidney function, inflammation, and uterine contractility. One of the
prostaglandins (PGE 1 ) is a potent pyrogen (fever-inducing agent), involved in the symp-
toms of many pathological processes.
Prostaglandin biosynthesis is also relevant to drug design. In nature, prostaglandins
are biosynthesized from arachidonic acid, a C20 unsaturated fatty acid. The synthetic
conversion of arachidonic acid to a prostaglandin is catalyzed by the cyclooxygenase
(COX) enzyme, which is itself an important target in the design of anti-inflammatory
drugs ranging from acetylsalicylic acid (8.4) to ibuprofen (8.5) to rofecoxib (8.6). In
addition, prostaglandin-like molecules, including the leukotrienes, thromboxanes, and
prostacyclin, are also important drug design targets for inflammatory disorders such as
asthma. Collectively, these are referred to as the eicosanoids.
8.1.4.4 Lipids: Terpenes
Terpenes are a diverse class of small organic molecules. Some are open-chain mole-
cules, some contain rings, some are purely hydrocarbons (classical terpenes), and some
ENDOGENOUS MACROMOLECULES 473Figure 8.3 Generalized structures of typical phospholipids.