Prostaglandin precursors, syntheses including

Mammals lack the enzymes to insert double bonds at carbon atoms beyond C-9 in the fatty acid chain. Thus they cannot synthesize linoleate and linole-nate, both of which have double bonds later in the chain than C-9 (linoleate has cis, cis A9, A12 double bonds, and linolenate has all-ris A9, A12, A15 double bonds). Hence, in mammals linoleate and linolenate are called essential fatty acids since they have to be supplied in the diet. These two unsaturated fatty acids are also the starting points for the synthesis of other unsaturated fatty acids, such as arachidonate. This C20 4 fatty acid is the precursor of several biologically important molecules, including the prostaglandins, prostacyclins, thromboxanes and leukotrienes (see Topic Kl). 

One important group of nutrients, rarely included in the Western diet, is the essential fatty acids. These compounds are precursors to prostaglandins, which inhibit testosterone binding in the prostate. They also act as anti-inflammatory agents and restrain protein synthesis and cell growth in the prostate. The omega-3 marine lipids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been shown to inhibit the growth of prostatic tumors. Flax seed, a rich source of essential fatty acids, has been shown to inhibit cancer metastasis in studies done with mice. 

The answer is e. (Murray, pp 230-267. Scrivei pp 2297-2326. Sack, pp 121-138. Wilson, pp 287-320.) In mammals, a variety of fatty acids are considered essential and cannot be synthesized. These include linoleate (C-I8 cis-A , A h and linolenate (C-I8 cis-A , A u A h Either these fatty acids or fatty acids for which they are precursors must be supplied in the diet as starting points lor synthesis of a variety ol other unsaturated fatty acids that lead to the synthesis of prostaglandins, thromboxanes, and leukotrienes. For example, arachidonate, a 20-carbon fatty acid with four... 

Although most hpids required for cell structure, fuel storage, or hormone synthesis can be synthesized from carbohydrates or proteins, we need a minimal level of certain dietary hpids for optimal health. These hpids, known as essential fatty acids, are required in our diet because we cannot synthesize fatty acids with these particular arrangements of double bonds. The essential fatty acids a-linoleic and a-linolenic acid are supphed by dietary plant oils, and eicosapentaenoic acid (ERA) and docosa-hexaenoic acid (DHA) are supplied in fish oils. They are the precursors of the eicosanoids (a set of hormone-like molecules that are secreted by cells in small quantities and have numerous important effects on neighboring cells). The eicosanoids include the prostaglandins, thromboxanes, leukotrienes, and other related compounds. 

The lactones shown in the Table include several representatives of recognized or potential value as starting materials in natural product synthesis. Lactone 1 is a precursor of grandisollactone 3 of some pyrethroids, lactone 6 of some prostaglandins, and lactone 7 of multistriatin, methynolide and monensin. ... 

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