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O
CO
2
H
CO
2
H
O
2
5-Lipoxygenase
CO
2
H
Arachidonic acid
Leukotriene A
2O
2
Cyclooxygenase
HO
2
C
O
OH
O
O
CO
2
H
O
O
H
H
OH
PGH
2
H
H
HO
OH
HO
PGI
2
H
HO
PGE
2
CO
2
H
O
O
OH
TXA
2
FIGURE 5.15
The prostaglandins.
fatty acid arachidonic acid (5, 8, and 11, 14-eicosatetraenoic acid) to generate eico-
sanoids. The metabolic pathway by which arachidonic acid is converted to the vari-
ous eicosanoids is complex.
These compounds constitute a very important family of physiologically potent
lipids and are present in minute amounts in most body tissues and possess important
functions in the body. Specifically, the prostaglandins are natural hormones with
very important biological effects. They lower gastric secretions, stimulate uterine
contractions, lower blood pressure, influence blood clotting, and induce asthma-like
allergic responses. They also act as mediators and exhibit a variety of physiological
effects, such as regulating the contraction and relaxation of smooth muscle tissue.
SUMMARY
In this chapter, two important groups of natural products are presented: the sugars
(carbohydrates) and fats (lipids). The carbohydrates include simple sugars, and mono-
and polysaccharides. The lipids include the fatty acids, the omega oils, and the
prostaglandins.
HISTORICAL NOTE
Prostaglandin derives its name from the prostate gland. It was first isolated in
1935 from prostate secretions. The first total syntheses of prostaglandin F
2α
and
prostaglandin E
2
were achieved in 1969. In 1971, it was determined that aspirin-
like drugs could inhibit the synthesis of prostaglandins, and this research work
by Samuelsson and Vane was recognized in the award of the Nobel Prize in 1982
for physiology and medicine.
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