The Di- and triesters of the lipids of steer and human meibomian glands |
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Authors: | N Nicolaides Evelyn C Santos |
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Affiliation: | (1) Department of Medicine (Dermatology), University of Southern California School of Medicine, 2025 Zonal Ave., 90033 Los Angeles, CA |
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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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