The eicosanoids: a historical overview.

Eicosanoids are biologically active compounds derived from 20 carbon unsaturated fatty acids, among which arachidonic acid is a substrate of particular importance. The history of the eicosanoids dates back to the thirties, when new biologically active compounds were found in human seminal plasma. These "prostaglandins" were purified, and their structures and mechanisms of biosynthesis were elucidated in the early sixties. Other eicosanoids, including thromboxane A2, a potent platelet aggregating agent, and prostacyclin, an antagonist to thromboxane A2, were discovered in the seventies. The inhibitory actions of acetylsalicylic acid on eicosanoid synthesis were also uncovered at this time. In 1979, a new metabolic sequence leading to the synthesis of a new group of eicosanoids, called leukotrienes, was reported. The leukotrienes have several biological activities, including the mediation of bronchoconstriction in allergic response. The eicosanoids comprise a diverse group of biologically active compounds; many of these arise from arachidonic acid, and are associated with injury, allergic responses, and platelet aggregation.