Fatty acid nitration is a recently discovered process that generates biologically active nitro
lipids; however, its mechanism has not been fully characterized. For example, some structural details such as vinyl and allyl isomers of the nitro
fatty acids have not been established. To characterize
lipids that originated from a biomimetic reaction of *NO(2) with
oleic acid, we synthesized several isomers of nitro
oleic acids and studied their chromatography and mass spectra by various techniques of mass spectrometry. LC/MS analysis performed on a high resolution micro column detected molecular carboxylic
anions of various
oleic acid nitro isomers (NO(2)OA). Esterification of NO(2)OA with
pentafluorobenzyl bromide and diisopropylethylamine as a catalyst produced a unique
isoxazole ester derivative exclusively from allyl NO(2)OA isomers via
dehydration of the nitro group at ambient temperatures. This new analytical procedure revealed that *NO(2) generated two vinyl and two allyl isomers of NO(2)OA. The vinyl isomers showed high regioselectivity with the 1.8:1 preference for the 10-NO(2)OA isomer that was absent among allylic isomers. The nitration also generated
elaidic acid via cis-trans isomerization and diatereoisomers of vicinal nitro hydroxy, nitro keto and alpha-nitro epoxy
stearic acids with high stereo and regioselectivity. Nitration of small unilamelar
phospholipid vesicles resulted in several
phospholipids containing nitro
lipids and
elaidic acid amenable to hydrolysis by
phospholipase A(2).