Plasmalogens are glycerophospholipids. They contain an ester-linked lipid at the SN2 position on the glycerol backbone (DHA or arachidonic acid) and a vinyl ether linked lipid at the SN1 position on the glycerol backbone (C16 palmitic acid or C18 oleic acid). Please see my attached picture.
To answer your question about how plasmalogens differ from DHA or Oleic acid: Both DHA and oleic acid can be parts of the plasmalogen. The DHA is bonded to the plasmalogen glycerol backbone at the SN2 position via an ester linkage and oleic acid can be bonded to the glycerol backbone at the SN1 position via a vinyl ether linkage. The plasmalogen is a much more complex structure than DHA or oleic acid!
