Abstract
Abstract: :
Purpose: The purpose of this study was to determine if oxidized derivatives of polyunsaturated fatty acids (PUFAs) exist in human meibum. Methods: Human meibum was collected from normal male patients and subjected to normal phase HPLC. Several PUFAs – arachidonic acid (AA, omega–6), linoleic acid (LA, omega–6), docosahexaenoic acid (DHA, omega–3) – and various derivatives of LA were used as model markers of lipid peroxidation (LP). An analytical routine based on a combination of high performance liquid chromatography (HPLC)and gas chromatography was developed to separate and analyze the lipids and their peroxidation products. The structures of the oxidized lipids were determined spectroscopically by utilizing UV spectrometry, mass spectrometry and NMR. Results: In the present study, human meibum was shown to contain a compound whose spectral properties and chromatographic behavior indicated that it was a monooxygenated polyunsaturated free fatty acid of unknown structure. A series of known and as well as novel LP markers derived from AA, LA, DHA and their derivatives was synthesized in an attempt to identify the compound. The metabolite did not coelute with any of the tested HPLC standards. Currently, its nature is being investigated by means of HPLC MS/MS analysis. Conclusions: For the first time, human meibum was shown to contain an oxidized PUFA that may have a regulatory effect on the human ocular surface cells and could alter integrity and stability of the tear film lipid layer.
Keywords: lipids • oxidation/oxidative or free radical damage • cornea: tears/tear film/dry eye