Chiral phase-HPLC separation of hydroperoxyoctadecenoic acids and their biosynthesis by fatty acid dioxygenases.

Fatty acid oxygenases are often characterized by steric analysis of their hydroxy or hydroperoxy metabolites. Chiral phase-HPLC (CP-HPLC) can be used to separate enantiomeric hydroperoxyoctadecenoic acids. This method is based on analysis of seven octadecenoic fatty acids with double bonds at positions 6Z to 13Z, which were oxidized to hydroperoxides by photooxidation. A stationary phase, Reprosil Chiral NR, was found to resolve these hydroperoxy fatty acids with 1-hydroperoxy-2-propene and with 3-hydroperoxy-1-propene elements so that the S hydroperoxy fatty acids consistently eluted before the R stereoisomers. The chiral selector has not been disclosed, but it is described as an aromatic chiral phase with π-donor and π-acceptor groups of Pirkle type. The MS(3) spectra of the hydroperoxides showed characteristic fragments, which were influenced by the distance between the hydroperoxy and the carboxyl groups and the relative position of the double bond. Octadecenoic fatty acids can be oxidized by fungal and bacterial dioxygenases to hydroperoxides with cis or trans double bond configuration. Steric analysis of the hydroperoxy metabolites can be performed by this method, and it can also be used for preparative purposes.