H2-isoprostanes

H2-isoprostane bicycUc endoperoxides, 612 hpid hydroperoxide determination, 681 Arene endoperoxides... 

PGH2 or H2-isoprostane R]= carboxylate side chain R = other side chain... 

Fig. 2.2 Rearrangement of bicyclic endoperoxides to form y-ketoaldehyde. Proposed mechanism for formation of y-ketoaldehydes from bicyclic endoperoxide such as PGFI2 and H2-isoprostanes by base-catalyzed concerted rearrangement (Salomon et al., 1984). Attack of base is shown at the top of the bridgehead, which results in formation of E2-isomers. Attack at the symmetrical position below the bridgehead forms the D2-isomers...

LG formation can be enhanced in this system by inhibition of thromboxane synthase. Because prostaglandin synthases do not act on H2-isoprostanes, the relative yield of IsoK derived from H2-isoprostane formed in cells is expected to be similar to that found in vitro. 

Alternatively, the 1,2-dioxolanyl radical can react with the double bond adjacent to the endoperoxide to create a highly unstable cyclopentane ring [13,17], The bicy-clic endoperoxides created in this reaction are analogous to prostaglandin H2 formed enzymatically by cyclooxygenases the resulting products, therefore, have been given the trivial name isoprostanes [18],... 

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