Sphingomyelin from milk-characterization of liquid crystalline,liposome and emulsion properties

The properties of sphingomyelin obtained from bovine milk were investigated. In particular, the properties of liposomes and emulsions prepared from the spingomyelin, as well as the liquid crystalline behavior, were investigated and compared to those of related phosphatidylcholine systems. Like sphingomyelins from other sources, sphingomyelin from milk contains a large fraction of long and saturated acyl groups, which results in a high gel-to-liquid crystal transition temperature (T_c 35–82°C, depending on the lipid concentration). At high sphingomyelin concentrations, a lamellar phase forms above T_c, while a swollen gel phase is obtained below T_c. The gel phase swells to about 20 wt% water, whereas the swelling continues to about 40 wt% water above T_c. The limiting areas per molecule are 51 and 68 Ų below and above T_c, respectively. Sphingomyelin from milk forms liposomes readily in the presence of cholesterol. The liposomes formed have a diameter of about 100 nm and are stable, even at 0.1 M NaCl or HCl. Materials entrapped in the liposomes are released rather slowly (typically 40% over 5 h). A comparison shows that the sphingomyelin liposomes behave similarly to those formed by phosphatidylcholine systems. Furthermore, sphingomyelin from milk forms stable oil-in-water emulsions with soybean oil. The size of the emulsion droplets obtained was about 200 nm. Both the size of the emulsion droplets and its dependence on electrolyte addition correlate closely with those of emulsions formed by the corresponding phosphatidylcholine system. Therefore, it is possible to use sphingomyelin as an alternative for saturated phosphatidylcholines, which may be advantageous for oral and dermal pharmaceutical applications, as well as in cosmetics.