The isoprostanes: a perspective.

The isoprostanes are a new class of natural products produced in vivo by a non-enzymatic free-radical-induced peroxidation of polyunsaturated fatty acid. In the case of arachidonic acid, for example, four classes of isoprostanes can be produced. Because of the specific structural features distinguishing them from other free-radical-generated products, e.g., HETEs, etc., the isoprostanes can provide an exclusive and selective index for the oxidant component of several inflammatory and degenerative diseases. The possible mechanisms of formation of the individual isoprostanes is discussed in detail. Class III products, such as 8-iso-PGF2 alpha and 8-iso-PGE2 have been shown to be vasoconstrictors and modulate platelet function. Several synthetic representatives from the four classes of arachidonic-acid-derived isoprostanes have already been prepared by total synthesis. These synthetic standards have been used for the identification and quantitation of these isoprostanes in biological fluids using gas chromatography/mass spectrometry methodology.