Production and structure elucidation of glycoglycerolipids from a marine sponge-associated Microbacterium species

The bacterium Microbacterium sp., isolated from the sponge Halichondria pan icea, produced four unusual cell-associated glycoglycerolipids and one diph osphatidylglycerol when grown on marine broth and on artificial seawater me dia. The lipids were isolated by chromatography on silica columns and their structures elucidated using a combination of multidimensional NMR and MS t echniques. The main compound was 1-O-acyl-3-[alpha-glucopyranosyl-(1-3)-(6- O-acyl-alpha-mannopyranosyl)]glycerol (GGL.2) with 14-methyl-hexadecanoic a cid and 12-methyl-tetradecanoic acid positioned at C-6 of the mannose unit and at the glycerol moiety. Glycolipid production was correlated with growt h and reached a maximum value of 200 mg/L when grown on artificial seawater medium with 20 g/L glucose. The main compound decreased the surface tensio n of water down to 33 mN/m and the interfacial tension of the water/n-hexad ecane system down to 5 mN/m. In addition to this good surface-active behavi or, the main glycoglycerolipid showed antitumor activities.