MURAMIC ACID

White Solid

Muramic acid is a marker for Gram-positive bacteria.

Muramic acid crystallises from H2O or aqueous EtOH as the monohydrate which loses H2O at 80o in vacuo over P2O5. It sometimes contains some NaCl. It has been purified by dissolving 3.2g in MeOH (75mL), filtering from some insoluble material, concentrating to ~10mL and refrigerating. The colourless crystals are washed with absolute MeOH. This process does not remove NaCl; to do so, the product is recrystallised from an equal weight of H2O to give a low recovery yield of very pure acid (0.12g). On paper chromatography 0.26_g give one ninhydrin positive spot after development with 75% phenol (RF 0.51) or with sec-BuOH/HCO2H/H2O (7:1:2) (RF 0.30). [Matsushima & Park Biochemical Preparations 10 109 1963, J Org Chem 27 3581 1962.] The acid has also been purified by dissolving 990mg in 50% aqueous EtOH (2mL), cooling, collecting the colourless needles on a sintered glass funnel and drying over P2O5 at 80o/0.1mm to give the anhydrous acid. [Lambert & Zilliken Chem Ber 93 2915 1960.] Alternatively the acid is dissolved in a small volume of H2O, neutralised to pH 7 with ion-exchange resin beads (IR4B in OH-form), filtered, evaporated and dried. The residue is recrystallised from 90% EtOH (v/v) and dried as above for 24hours. [Strange & Kent Biochem J 71 333 1959.] The N-acetyl derivative (NAMA, R-2-(acetylamino)-3-O -(1-carboxyethyl)-2-deoxy-D-glucose, R -2(2 -acetylamino-2-deoxy -D-glucose -3-yloxy)-propionic acid) [10597-89-4], M 292.3, has m ~125o (dec) and [] 20D +41.2o after 24hours (c 1.5, H2O), pKEst ~ 3.6. [Watanabe & Saito J Bacteriol 144 428 1980, Beilstein 4 IV 2029.]