Galactolipids are a type of glycolipid whose sugar group is galactose. They differ from glycosphingolipids in that they do not have nitrogen in their composition.[1]
They are the main part of plant membrane lipids where they substitute phospholipids to conserve phosphate for other essential processes. These chloroplast membranes contain a high quantity of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG).
They probably also assume a direct role in photosynthesis, as they have been found in the X-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) revealed alpha-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 same galactolipid, 1,2-di-O-α-linolenoyl-3-O-α-D-galactopyranosyl-sn-glycerol,[5] may be important for the anti-inflammatory activity of Dog Rose (Rosa canina), a medicinal plant with documented effect on inflammatory diseases such as arthritis.
The galactosphingolipid galactocerebroside (GalC) and its sulfated derivative sulfatide is also in abundance present (together with a small group of proteins) in myelin, the membrane around the axons in the nervous systemofvertebrates.[6]
It is galactolipids, rather than phlorotannins, that act as herbivore deterrents in Fucus vesiculosus against the sea urchin Arbacia punctulata.[7]
