Abstract
Three groups of diesters have been isolated and identified in the lipids of steer meibomian glands. The first group, designated as α Type I, with the abbreviated formula FA-αOHFA-FA1c, consisted of α-hydroxy fatty acids esterified to fatty acids and fatty alcohols in the approximate molar ratio 1∶1∶1. The second group, designated as ω Type I-St, with the abbreviated formula FA-ωOHF A-St, consisted of ω-hydroxy fatty acids esterified to fatty acids and sterols in the approximate molar ratio 1∶1∶1. The third group, designated as α,ω Type II, with the abbreviated formula FA-α,ωdiol-FA, consisted of α,ω-diols esterified to 2 moles of fatty acids. The sum of the different diesters comprised about 9% of total steer meibomian lipids.
Capillary GLC of the fatty acids of αType I diesters showed the fatty acids to be a family with a two-cluster profile, one at C12 to C20 and the other at C21 to C31, with anteiso chains predominating. Fatty acids from ωType I-St and α,ωType II diesters gave mainly a one-cluster profile in the short long chain, C23 to C30, with anteiso chains predominating, while the α-hydroxy fatty acids were short chain C13 to C18 acids with C16 predominating. The sterols in diesters ωType I-St were cholesterol (∼60%), Δ7 cholestenol (∼35%) and an unidentified compound (∼5%) with a GLC retention time slightly longer than Δ7 cholestenol on SE-30 phase. The ω-hydroxy fatty acids and α,ω-diols both were of exceedingly long chain lengths, C29−C38, and showed similar GLC profiles. Two types of triesters comprising approximately 1% of total steer meibomian lipids have been isolated but incompletely characterized. In terms of molar ratios, one group of triesters gave fatty acids:ω-hydroxy fatty acids:α-hydroxy fatty acids:sterols + fatty alcohols as approximately 1∶1∶1∶1. The other contained fatty acids, α-hydroxy fatty acids and α,ω-diols in what appears to be a complex mixture of several triesters. Diesters ωType I and α,ωType II also were found in human meibum. Hitherto these two diesters have not been found in any animal tissue.
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Abbreviations
- FA:
-
fatty acid
- FA1c:
-
fatty alcohol
- St:
-
sterol
- Chol:
-
cholesterol
- FAME:
-
fatty acid methyl ester(s)
- SE:
-
sterol ester(s)
- WE:
-
wax ester(s)
- TG:
-
triacyl glycerol(s)
- C:
-
chloroform
- M:
-
methanol
- HAc:
-
acetic acid
- TLC:
-
thin layer chromatography
- ANS:
-
aniline naphthalene sulfonic acid
- GLC:
-
gas liquid chromatography
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Nicolaides, N., Santos, E.C. The Di- and triesters of the lipids of steer and human meibomian glands. Lipids 20, 454–467 (1985). https://doi.org/10.1007/BF02534237
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DOI: https://doi.org/10.1007/BF02534237