High-performance capillary electrophoresis of sialylated oligosaccharides of human milk

Oligosaccharides in human milk inhibit enteric pathogens in vitro and in vi vo. Neutral milk oligosaccharides vary among individuals and over the cours e of lactation. To study such variation in the acidic milk oligosaccharides , a sensitive, convenient, quantitative method is needed. High-performance capillary electrophoresis of underivatized acidic oligosaccharides with det ection by UV absorbance at 205 nm proved to be sensitive to the femtomole l evel. Eleven standard oligosaccharides ranging from tri- to nonasaccharide (3'-sialyllactose, 6'-sialyllactose, 3'-sialyllactosamine, 6'-sialyllactosa mine, disialyltetraose, 3'-sialyl-3-fucosyllactose, sialyllacto-N-tetraose- a, sialyllacto-N-tetraose-b, sialyllacto-N-neotetraose-c, disialyllacto-N-t etraose, and disialomonofucosyllacto-N-neohexaose) were resolved; baseline resolutions of 3'-sialyllactose, 6'-sialyllactose, and other structural iso mers were achieved. Peak areas were linear from 30 to 2000 pg and were repr oducible with a coefficient of variation between 4 and 9%. There was no evi dence of quantitative interference of one oligosaccharide with another. In studies using pooled human milk, addition of in creasing amounts of authent ic standard oligosaccharides produced the expected positive increments in d etected values, indicating quantitative recovery without interference by ot her milk components. The identities of the major sialylated acidic oligosac charides of pooled human milk agreed with the results of previous studies e mploying other analytical methods. Comparison of oligosaccharide profiles o f milk samples from different donors revealed extensive variation, especial ly in the structural isomers of sialyllacto-N-tetraose. This sensitive, hig hly reproducible method requires only simple sample workup and is useful in defining variations in human milk acidic oligosaccharides and investigatin g their possible relationship with diseases of infants. (C) 2000 Academic P ress.