Quantitative Determination of Sialic Acid in the Monosialoganglioside, GM1, by the Thiobarbituric Acid Method

Several methods for the quantitative analysis of sialic acids in glycoconjugates require that the sialic acid glycosidic bond be cleaved prior to assay. The conventional (L. Svennerholm, (1958) Acta Chem. Scand. 12, 547-554) procedure for the hydrolysis of complex carbohydrates such as gangliosides employs 0.1 n H+ at 80 degrees C for 60 min. Under these conditions, we find that the monosialoganglioside (GM1) yields less than 50% of the total sialic acid. However, 90% recovery of sialic acid was achieved by supplementing the hydrolysis mixture with 0.2% sodium dodecylsulfate (SDS) and increasing the temperature to 85 degrees C. During hydrolysis under these conditions, N-acetylneuraminic acid (NAN) is degraded at about 7% per hour. If the analytical values for GM1 are corrected for degradation, the recovery of NAN is essentially quantitative.