Galactolipids are a type ofglycolipid whose sugar group isgalactose. They differ fromglycosphingolipids in that they do not havenitrogen in their composition.[1]
They are the main part of plantmembrane lipids where they substitute phospholipids to conserve phosphate for other essential processes. Thesechloroplast membranes contain a high quantity of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG).
They probably also assume a direct role inphotosynthesis, as they have been found in theX-ray structures of photosynthetic complexes.[2]
Galactolipids are more bioavailable than free fatty acids, and have been shown to exhibit COX mediated anti-inflammatory activity.[3] Bio-guided fractionation of spinach leaves (Spinacia oleracea) revealedalpha-linolenic acid galactolipids (18:3, n-3) were responsible for inhibitory effects on tumor promoter-induced Epstein-Barr virus (EBV) activation.[4] Recently, it has been demonstrated that this samegalactolipid, 1,2-di-O-α-linolenoyl-3-O-α-D-galactopyranosyl-sn-glycerol,[5] may be important for the anti-inflammatory activity ofDog Rose (Rosa canina), a medicinal plant with documented effect on inflammatory diseases such as arthritis.
The galactosphingolipidgalactocerebroside (GalC) and its sulfated derivative sulfatide is also in abundance present (together with a small group of proteins) inmyelin, the membrane around theaxons in thenervous system ofvertebrates.[6]
It is galactolipids, rather thanphlorotannins, that act asherbivore deterrents inFucus vesiculosus against the sea urchinArbacia punctulata.[7]