Prostaglandins are eicosanoids containing a 20-carbon cyclopentane ring that are produced by cells and act as local hormones. They are produced from arachidonic acid through a cyclic pathway involving prostaglandin H2. Prostaglandins perform various functions like regulating blood pressure, inflammation, reproduction, and gastric secretion. Non-steroidal anti-inflammatory drugs like aspirin and ibuprofen inhibit prostaglandin production by blocking cyclooxygenase. Aspirin irreversibly acetylates cyclooxygenase, while ibuprofen blocks the channel for arachidonic acid entry.

2. 
 Prostaglandins and related compounds are collectively known
as eicosanoids, they all contain 20C parent cyclopentane ring.
 Discovered by Ulf Von Euler (1930), extracted from human
semen (prostate gland).
 Produced & released by nearly all mammalian cells;(Except
RBCs)
 Perform a variety of functions
 Produced in minute amounts and are not stored.
 Have a half-life of 5 minutes or less, hence they are destroyed
very rapidly in the body.
INTRODUCTION

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CLASSIFICATION

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 The structure of PG is based on 20C parent saturated acid
called “Prostanoic Acid”
STRUCTURE
 All PGs are 20C fatty acids containing a cyclopentane
ring.
 All PGs have:
 -OH group at 15th position, some at 19th
 trans double bond at 13th position

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BIOSYNTHESIS OF PROSTAGLANDINS

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 Arachidonic acid (precursor for most of the
prostaglandins)
 Arachidonic acid is released from membrane bound
phospholipids by phospholipase A2.
 It occurs due to a specific stimuli by hormones
(epinephrine or bradykinin)
 Oxidation & cyclization of arachidonic acid to PGG2
which is then converted to PGH2 by peroxidase.
BIOSYNTHESIS OF PROSTAGLANDINS

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 PGH2 (immediate precursor for the synthesis of a
number of prostaglandins, including prostacyclins &
thromboxane)
 This is known as cyclic pathway of arachidonic acid.
CONTD…

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 Act as local hormones:
 Regulation of blood pressure : PGE, PGA & PGl2 increased
blood flow and decreased peripheral resistance to lower the
blood pressure.
 Inflammation: PGEI & PGE2 induce the symptoms of
inflammation (redness, swelling, edema etc.) due to arteriolar
vasodilation.
 Reproduction: PGE2 & PGF2 are used for the medical
termination of pregnancy & induction of labor.
 Regulation of gastric secretion: PGs stimulate pancreatic
secretion & increase the motility of intestine which often causes
diarrhea.
BIOCHEMICAL ACTIONS OF
PROSTAGLANDINS

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 Influence on immune system: Macrophages secrete PGE
which decreases the immunological functions of B-& T-
lymphocytes.
 Platelet Aggregation:
 PGI2: Inhibit Aggregation (Released by endothelial cells)
 PGE2 & TXA2: ( Promote Clotting Process)
CONTD…

10. 
(NSAIDs)
 Non-steroidal anti-inflammatory drugs
(NSAIDs), such as aspirin and derivatives
of ibuprofen, inhibit cyclooxygenase
activity of PGH2 Synthase.
• They inhibit formation of prostaglandins
involved in fever, pain, & inflammation.
 Ibuprofen and related compounds block
the hydrophobic channel by which
arachidonate enters the cyclooxygenase
active site.
INHIBITOR(S)
CH
COOH
H3C
CH2
CH
CH3
H3C
Ibuprofen

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12. 
 Aspirin acetylates a serine hydroxyl group near the active site,
preventing arachidonate binding.
 The inhibition by aspirin is irreversible.
Anti inflammatory Drugs inhibit Eicosanoid Synthesis

13. 
 Yes aspirin-like drugs inhibited the formation of
prostaglandins , but it does have some side effects.
 Aspirin is not recommended for patients with low risk of heart
attack or stroke or those having history of gastric ulcers or have
genetic problem like clotting such as Hemophilia.
 Aspirin is not also recommended for babies and children
because it may cause Reye’s syndrome which involves life
threatening damage to both the liver and brain
CONCLUSION

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