Prostaglandin-like compounds

Although the acute vasodilator effects, as shown in in vitro studies (see above), may participate in the antihypertensive effects, the reduced blood pressure persisted even 42-48 h after the last administration of quercetin, when the plasma quercetin concentration and its metabolites fell bellow 25% of the peak post-administration levels [43]. Furthermore, the antihypertensive effects of quercetin did not appear to be related to its antioxidant properties since quercetin did not lower the urinary isoprostane F20 excretion, a prostaglandin-like compound produced in a non enzymatic reaction of arachidonic acid in membrane lipids and superoxide, which is currently used as a reliable marker of oxidative stress. The mechanisms involved in the antihypertensive effects and protection from organ damage... 

The standard nomenclature for this family of readily released fatty acids from tissues and organs and the synthetic prostaglandin-like compounds is derived from the C-20 cyclopentane acid skeleton of the hypothetical prostanoic acid 1. 

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo via a nonenzymatic mechanism involving the free radical-initiated peroxidation of arachidonic acid. This article summarizes our current knowledge of these compounds. Herein, a historical account of their discovery and the mechanism of their formation are described. Methods by which these compounds can be analyzed and quantified are also discussed, and the use of these molecules as biomarkers of in vivo oxidant stress is summarized. In addition to being accurate indices of lipid peroxidation, some isoprostanes possess potent biological activity. This activity will be discussed in detail. Finally, in more recent years, isoprostane-like compounds have been shown to be formed from polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexaenoic acid. These findings will be summarized as well. 

The complex mixture of regioisomers and stereoisomers structurally related to the endoperoxides and thromboxanes (prostaglandin-like compounds) produced from arachidonic acid and esterified to phospholipids and cholesterol are classified as isoprostanes. These compounds are used as markers of in vivo oxidative injury in biological systems and considered reliable because they are specific, stable and not affected by the lipid content of the diet (Chapter 13. E.4). However, these secondary oxidation products are produced in relatively small concentrations because they are derived from arachidonic acid, which is a minor polyunsaturated lipid compared to linoleic acid in biological samples. Very sensitive gas chromatography-mass spectrometric (GC-MS) and liquid chromatography-MS techniques are required to analyse isoprostanes in biological samples. 

C. parvum is unique in another aspect, connected with medicine, namely, in its ability to synthesize prostaglandin-like compounds (PLC). 

Hatanaka H, Wang E, Taniguchi M, lijima S and Kobayashi T (1988) Production of vitamin Bi2 by a fermentation with a hollow-fiber module. Appl Microbiol Biotechnol 27 470-473 Hellgren L and Vincent J (1983) New group of prostaglandin-like compounds in Propionibacterium acnes. Gen Pharmacol 14 207-208 Herve C, Gautier M, Coste A and Rouault A (1998) Lysogeny of propionibacteria. Abstr 2nd Int Symp Propionibacteria, Cork, Ireland... 

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