Submitted on May 21, 2009
Revised on January 1, 1998
Accepted on June 16, 2009
Human tear film and meibum. I. Very long chain wax esters and (O-acyl)-omega-hydroxy fatty acids of meibum
Igor A. Butovich, Jadwiga Wojtowicz, and Mike Molai
Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057
Corresponding Author: igor.butovich{at}utsouthwestern.edu
Human meibum was targetly analyzed for the presence of intact WE and related compounds by using reversed phase high-performance liquid chromatography in combination with ion trap mass spectrometry. The major detected WE were based on C18:n (n=1-4) unsaturated fatty acids (FA) ranking in the following order of abundance: C18:1>C18:2>C18:3>C18:4. The major fatty alcohols (FAl) found in WE were of saturated nature and varied from C18:0 to C28:0. The three most abundant species were C18:1-FA esters of C24:0, C25:0, and C26:0-FAl. Typically, a major compound based on C18:1-FA and a saturated FAl was accompanied by a few related compound based on a C18:2, C18:3, and C18:4-FA. Contrary to the previous reports, no epoxy-WE or epoxy-FA were detected in fresh and 1-year old meibum samples. More than twenty (O-acyl)-
-hydroxy-FA (OAHFA) were observed. The main OAHFA were based on very long chain -hydroxy-FA (C30:1, C32:1, and C34:1, correspondingly) acylated through their omega-hydroxyls by a C18:1-FA. Due to their amphiphilic anionogenic nature, OAHFA may be responsible for stabilization of the tear film lipid layer by creating an interface between the vast pool of strictly nonpolar lipids of meibum (WE, CE, etc) and the aqueous subphase beneath it – a role previously attributed to phospholipids.
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