galactolipid
File:monogalactosyl diacylglycerol.png
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.{{cite web|url=http://www.ghr.nlm.nih.gov/glossary=galactolipids|title=Galactolipids|date=21 December 2009|work=Genetics Home Reference|publisher=U.S. National Library of Medicine|access-date=25 December 2009|archive-date=5 September 2015|archive-url=https://web.archive.org/web/20150905154800/http://ghr.nlm.nih.gov/glossary=galactolipids|url-status=dead}}
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.{{Cite journal
| last = Dörmann
| first = Peter
|author2=Christoph Benning
| title = Galactolipids rule in seed plants
| journal = Trends in Plant Science
| volume = 7
| issue = 3
| pages = 112–118
| date = 1 March 2002
| pmid = 11906834| doi = 10.1016/S1360-1385(01)02216-6
}}
Galactolipids are more bioavailable than free fatty acids, and have been shown to exhibit COX mediated anti-inflammatory activity.Christensen, L. [https://pubmed.ncbi.nlm.nih.gov/20653526/ Galactolipids as Potential Health Promoting Compounds in Vegetable Food]s Recent Patents on Food, Nutrition & Agriculture, 2009; 1, 50-58. 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.Wang R, Furomoto T, Motoyama K, Okazaki K, Kondo A, Fukui H. Possible anti-tumor promoters in Spinacia oleracea (spinach) and comparison of their contents among cultivars. Biosci Biotechnol Biochem 2002; 66(2): 248-254. Recently, it has been demonstrated that this same galactolipid, 1,2-di-O-α-linolenoyl-3-O-α-D-galactopyranosyl-sn-glycerol,Block G, Patterson B, Subar A. Fruit, vegetables, and cancer prevention: A review of the epidemiological evidence. Nutr Cancer 1992; 18(1): 1-29. 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 system of vertebrates.{{Cite journal
| last = Coet
| first = Timothy
|author2=Kunihiko Suzukia |author3=Brian Popkoa |author4=Kunihiko Suzukib |author5=Brian Popkoc |author6=Kunihiko Suzukid |author7=Brian Popko
| title = New perspectives on the function of myelin galactolipids
| journal = Trends in Neurosciences
| volume = 21
| issue = 3
| pages = 126–130
| date = 1 March 1998
| pmid = 9530920| doi = 10.1016/S0166-2236(97)01178-8
}}
It is galactolipids, rather than phlorotannins, that act as herbivore deterrents in Fucus vesiculosus against the sea urchin Arbacia punctulata.Galactolipids rather than phlorotannins as herbivore deterrents in the brown seaweed Fucus vesiculosus. Michael S. Deal, Mark E. Hay, Dean Wilson and William Fenical, Oecologia, June 2003, Volume 136, Issue 1, pages 107-114, {{doi|10.1007/s00442-003-1242-3}}