Taurocholic salt-phospholipid-cholesterol-water solubilized systems were used to investigate the physical/chemical behavior of bile. Phase separation that produces float and precipitation was observed in the system. Analysis using FT-IR spectroscopy and GC-MS methods showed that aliphatic acids were principal component of the float. This demonstrated that hydrolysis of phospholipid must have occurred in the system. Considering that phospholipid plays a very important role in solubilizing cholesterol in bile, whereas aliphatic acids can not solubilize cholesterol, we suggest that the hydrolysis of phospholipid may be related to the formation of gallstone.

Key words: BILE ACID, PHOSPHOLIPID, CHOLESTEROL, IR