Prostaglandins

Prostaglandins belong  to a subclass of  lipids known  as the eicosanoids because of their structural similarities to  the C-20  polyunsaturated  fatty acids, the  eicosanoic acids. Prostaglandins are known to occur in almost all tissues in very small quantities
and have important physiologic and pharmacologic activities. These are synthesized in  vivo  by  cyclization  of  arachidonic  acid, which  is  either derived  from  dietary linoleic acid or  ingested as such, to  form a cyclopentane ring. There are three fatty
acids  known  as  eicosanoic acids (characterized by  the number  of double  bonds present  in  the  structure), which by joining with  the cyclopentane ring, gives rise to three groups of prostaglandins viz. PGI, PG2, PG3. These are listed in Table:-