Significant Surface Activity Shown by the Mixture of Partially Deacylated Lipids

Introduction and Summary

It is known that the existence of lecithin is essential for intestinal fat absorption^{1 8 9 11 12 13}. Oil and fat, both dietary and biliary phospholipids (PLs), are partially hydrolyzed by lipases and phospholipase A-2 (PLA2) in the small intestine, and are changed into fatty acids (FAs), monoglycerides (MGs) and lysophospholipids (LPs). These deacylated lipids are solubilized into mixed bile salt micelles^{2 6 14}. Because of the ubiquitous existence of PLA2, in all cells³, the mixed solution of LPs and FAs may be very common. We examined the surface activity, in paticular, immersional and adhesional wettability, shown by an aqueous solution of soy lysophospholipid (SLP)/MG/FA, SLP/FA and SLP/MG, in vitro, and found that many lipid mixtures (compositions) showed significant surface activity when their MG and FA components consisted of unsaturated FA(ULFA) and/or medium chain FA(MCFA). A lipid mixture SLP/ medium chain MG (MCMG)/MCFA showed the highest surface activity. Wettability decreased rapidly when the moiety of saturated long chain FA in lipid mixtures increased. The higher ratio of MG and FA to SLP gave higher activity, and the addition of a solubilizer, such as bile salt, was necessary to dissolve them in water. The result of this study suggests that the surface activity of these mixed micelles affects intestinal digestion and absorption, and subsequently alters the level of the physiological phenomena which take place at the cell membrane.