Steric analysis of 8-hydroxy- and 10-hydroxyoctadecadienoic acids and dihydroxyoctadecadienoic acids formed from 8R-hydroperoxyoctadecadienoic acid by hydroperoxide isomerases

8-Hydroxyoctadeca-9Z,12Z-dienoic acid (8-HODE) and 10-hydroxyoctadeca-8E,12Z-octadecadienoic acid (10-HODE) are produced by fungi, e.g., 8R-HODE by Gaeumannomyces graminis (take-all of wheat) and Aspergillus nidulans, 10S-HODE by Lentinula edodes, and 10R-HODE by Epichloe typhina. Racemic [8(-2)H]8-HODE and [10(-2) H]10-HODE were prepared by oxidation of 8- and 10-HODE to keto fatty acids by Dess-Martin periodinane followed by reduction to hydroxy fatty acids with (NaBH4)-H-2. The hydroxy fatty acids were analyzed by chiral phase high-performance liquid chromatography-tandem mass spectrometry (HPLC MS/MS) with 8R-HODE and 10SHODE standards. 8R-HODE eluted after 8S-HODE on silica with cellulose tribenzoate (Chiralcel 013-H), and 10S-HODE eluted before 10R-HODE on silica with an aromatic chiral selector (Reprosil Chiral-NR). 5S,8R-Dihydroxyoctadeca-9Z,12Z-dienoic acid (5S,8R-DiHODE) is formed from 18:2n-6 by A. nidulans and 8R, 11S-dihydroxyoctadeca-9Z, 12Z-dienoic acid (8R, 11S-DiHODE) by Agaricus bisporus. 8R-Hydroperoxylinoleic acid (8R-HPODE) can be transformed to 5S,8R-DiHODE and 8R,11-DiHODE by Aspergillus spp., and 8R, 13-dihydroxy-9Z, 11E-dienoic acid (8R, 13-DiHODE) can also be detected. We prepared racemic [5,8-(2)H2]5,8- and [8,11 -H-2,]8,11 -DiHODE by oxidation and reduction as above and 8R, 13S- and 8R, 13R-DiHODE by oxidation of 8R-HODE by S and R lipoxygenases. The diastereoisomers were separated and identified by normal phase HPLC-MS/MS analysis. We used the methods for steric analysis of fungal oxylipins. Aspergillus spp. produced 8R-HODE (>95% R), 10R-HODE (>70% R), and 5S,8R- and 8R,11S-DiHODE with high stereoselectivity (>95%), whereas 8R,13-DiHODE was likely formed by nonenzymatic hydrolysis of 8R,11S-DiHODE. (C) 2007 Elsevier Inc. All rights reserved.