This review article covers two topics concerning new surfactants developed by the author's group. First, amphiphilic monoaza crown ethers and alcohol ethoxylate derivatives are mentioned as a series of “functional” surfactants that have additional extra functions such as complexing ability toward metal ions, catalytic activity for organic reactions, and so on, besides basic surface-active properties. Second, high-performance double- or triple-chain surfactants bearing two or three ionic head groups which exhibit various interesting properties are introduced. These surfactants are prepared from diepoxy compounds according to the conventional procedures. Double- or triple-chain compounds bearing two head groups have higher hydrophilicity, lower cmc, and equal or greater ability to lower surface tension than conventional single-chain surfactants bearing the corresponding one head group. Other interfacial properties and their application to analytical chemistry are also described.
The surface properties and structures of mixed monolayers were studied to establish an assembled model for a detergent system. Surface pressure-area curves of the mixed monolayers of arachidic acid and cellulose derivatives showed a sinuous aspect with apparent inflection points. The curves of the mixed monolayers were consistent with the isotherms calculated on the assumption of the fractional summation in isotherms of pure monolayers, thus demonstrating the separation of molecules in a mixed monolayer, LB films with a single layer were prepared as a mixed monolayer of arachidic acid and cellulose derivative at a mixing ratio of 1/1. The monolayer was transferred onto a specimen grid covered with carbon supporting film at different surface pressures by the horizontal attachment method. LB film structures were then observed by dark-field electron microscopy. Micrographs of the films indicated inhomogeneous structures, thus showing phase separation in the mixed monolayer. The microscopically phase-separated monolayer would thus appear usable as a model detergent system in which arachidic acid is incorporated into the cellulose derivative.
Phospholipase D is known to transfer a phosphatidyl group of phospholipid to a hydroxy compound. Kojic acid (KA) is a hydroxy compound which has antimicrobial activity and shows inhibitory effect on tyrosinase. By using the transfer reaction from phosphatidylcholine (PC) to KA, we synthesized five 1, 2-diacylglycero-3-phosphoryl derivatives of KA, which have different acyl groups, i.e., PK 4 (dibutyloyl), PK 6 (dihexanoyl), PK 8 (dioctanoyl), PK 10 (didecanoyl) and PK 18 which was prepared from soybean PC. Membrane perturbation potency of the PKs was examined by using rat-liver mitochondria as a model biomembrane. PK 8 and PK 10 exhibited the potency, while KA, PC, PK 4 and PK 6 did not. It is known that the antimicrobial activity of some compounds is brought about by their membrane perturbation action. However, PK 8 and PK 10 did not show antimicrobial activity. The inhibitory effect on tyrosinase of the PKs was also tested. All of the PKs suppressed tyrosinase. It is considered that the inhibitory action of KA is due to its chelation with copper of the enzyme. The oxidation of unsaturated fatty acid is accelerated by some metal ions such as copper and ferrous. PK 18 has chelation potency with copper ion, and it is soluble in oil. Therefore, PK 18 was expected to be a metal inactivator in oil. As a result of oxidation test of soybean oil and methyl oleate containing copper acetate, PK 18 was shown to be an effective metal inactivator.
The mechanism for the self-assembly of the lamellar structure of intercellular stratum corneum lipids (SCL) has been a subject of considerable interest. The present study was conducted for clarification of this point using a synthetic pseudo-ceramide (SLE). The phase behavior and the structural characteristics of SLE other major components of SCL, fatty acids, cholesterol and cholesteryl esters, were studied by differential scanning calorimetry (DSC) and X-ray analysis. Stable lamellar structures could be confirmed only in the mixed systems of SLE and long-chain saturated fatty acids (stearic acid and palmitic acid). Lipid mixtures whose saturated fatty acid had been replaced by oleic acid failed to form lamellar structures and crystals of SLE were found present within these mixtures. It thus follows that fatty acids, as well as ceramides are essential to the self organization of SCL and that stable bilayer formation depends considerably on fatty acid molecular structure.
New vitamin E was isolated and purified from palm and rice bran oils by column chromatography and preparative HPLC. Structural determination was made by UV, MS and 1-H-NMR spectroscopy as 2, 5, 7, 8- tetramethy1-2- (4', 8', 12'-trimethyltrideca-11'-enyl) -6-chromanol.
Mutual coagulation of substrates and particles has been investigated in various liquids. Spherical polyethylene or nylon 12 particles and polyvinylidene chloride or quartz substrates were used. The number of particles adhering to a substrate as a measure of mutual coagulation was small in n-alcohols, whereas large in n-alkanes, carbon tetrachloride and water. Mutual coagulation decreased with increasing ethanol concentration in ethanol/water mixtures. The experimental results were not explained on the basis of the heterocoagulation theory, suggesting that the polar interaction affected mutual coagulation. The results are discussed from the standpoint of liquid dielectric constants as a measure of polarity. Mutual coagulation in the present systems was found to occur hardly in the liquids whose relative dielectric constants ranged from 20 to 60.