The compositions of the triacylglycerol (TAG) and triterpene ester (TE) fractions of the kernel fats (n-hexane extracts; shea butter) of the shea tree (Vitellaria paradoxa; Sapotaceae) were determined for 36 samples from seven sub-Saharan countries, i.e., Cote d’ Ivoire, Ghana, Nigeria, Cameroun, Chad, Sudan, and Uganda. The principal TAGs are stearic-oleic-stearic (SOS; mean 31.2 %), SOO (27.7 %), and OOO (10.8 %). The TE fractions contents are in the range of 0.5–6.5 %, and contain α-amyrin cinnamate (1c; mean 29.3%) as the predominant TE followed by butyrospermol cinnamate (4c; 14.8 %), α-amyrin acetate (1a; 14.1 %), lupeol cinnamate (3c; 9.0 %), β-amyrin cinnamate (2c; 7.6 %), lupeol acetate (3a; 7.2 %), butyrospermol acetate (4a; 5.8 %), and β-amyrin acetate (2a; 4.9 %). Shea kernel fats from West African provenances contained, in general, higher levels of high-melting TAGs such as SOS, and higher amount of TEs than those from East African provenances. No striking regional difference in the composition of the TE fractions was observed.
We have investigated the structure and rheology of diglycerol monolaurate (C12G2) reverse micelles in styrene using small-angle X-ray scattering (SAXS) and rheometry techniques. The SAXS data have been evaluated by generalized indirect Fourier transformation (GIFT) method and further supported by geometrical model fittings. We found that the C12G2 when added into styrene spontaneously self-assemble into ellipsoidal prolate type reverse micelles under ambient conditions. Micelles grew and micellar aggregation number (Nagg) increased with the increase in surfactant concentration demonstrating concentration induced one dimensional micellar growth, which was further supported by rheology data; the relative viscosity, ηr, for the C12G2/styrene mixtures exhibit far steeper concentration dependence behavior than those predicted for a dispersion of spherical particles based on the Krieger–Dougherty relation, due to the elongated micellar structures. On the other hand, a distinct modulation in the shape and size of micelles favoring ellipsoidal prolate-to-sphere type transition was observed upon heating, whose scheme could be attributed to the enhanced penetration tendency of oil into the lipophilic shell of the surfactant at the higher temperatures. As anticipated reverse micelles swelled with water causing two dimensional micellar growth; both the maximum dimension and maximum core radius increase with water.
The transparency of oil in cubic (O/I1) emulsions formed in water/C12EOn/isododecane systems (n=7, 9) with glycerol was investigated in order to understand the relation between surfactant hydrophilicity and transparency of the emulsion. In the C12EO7 system, O/I1 emulsions prepared in the I1+O region are milky when glycerol is not added. However, in the presence of glycerol, transparency increases with an increasing amount of glycerol because glycerol increases the refractive index of the I1 phase until it gradually approaches that of the oil phase. However, a phase transition to the hexagonal phase takes place before the refractive indices match; therefore, a transparent emulsion is not obtained. On the other hand, in the C12EO9 system, a transparent emulsion was prepared by adding glycerol because the refractive index of the I1 phase matches that of the oil before the phase transition. Since long EO chains are required to maintain the large curvature of the I1 phase against the addition of glycerol, a highly hydrophilic surfactant is required for the preparation of transparent emulsions. We also found that the viscosity of the O/I1 emulsion decreases with the decreased viscosity of the I1 phase obtained by adding glycerol. The low viscosity of the I1 phase in the presence of glycerol could be related to an increase in the maximum oil solubilization into the I1 phase.
Anionic gemini surfactants with carboxylic acid headgroups have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an ester bond, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via disuccinyl units. The surfactants exhibit pH-dependent protonation–deprotonation behavior in aqueous solutions. In alkaline solutions (pH 9 in the presence of 10 mmol dm–3 NaCl as the background electrolyte), the surfactants can lower the surface tension as well as form molecular assemblies, even in the region of low surfactant concentrations. Under acidic (pH 3) or neutral (pH 6–7) conditions, the surfactants are intrinsically insoluble in aqueous media and form a monolayer at the air/water interface. In this study, we have investigated physicochemical properties such as the function of the hydrocarbon chain length by means of static surface tension, pyrene fluorescence, dynamic light scattering, surface pressure–area isotherms, and infrared external reflection measurements.
Various protein solutions were studied in order to quantify the emulsifying activity of proteins, and to explore oil-water interfacial tension, oil particle size analysis, and oil phase separation behaviors in protein-stabilized oil-in-water (O/W) emulsions. Three proteins, bovine serum albumin (BSA), β-lactoglobulin (β-lg), and β-casein (β-ca), were employed to disperse hexadecane in various pH and ionic strength solutions in a wide range of oil-water ratios. It was confirmed that the volume mean oil droplet diameter, d43, changed depending on the oil content, the pH, the ionic strength, and the used protein. In a dilute protein solution (0.01 %) at pH 7, droplet size increased with oil content in so-called surfactant-poor regimes (e.g., above 5%, 10%, and 20% oil content for BSA, β-lg, and β-ca emulsion, respectively) but remained constant at ca. 10 mm, 6 mm, and 20 mm, respectively, in lower oil content surfactant-rich regimes. In surfactant-poor regimes, the most important factor determining the oil drop size was the threshold amount of protein adsorption onto the oil-water interface. In surfactant-rich regimes, on the other hand, it is suggested that drop size may be governed mainly by the mechanical strength of protein films covering the oil drops during emulsification, and this was quantified by the critical osmotic pressure, PCR. In this study, the PCR was measured conveniently in the oil phase separation experiments for protein-stabilized emulsions using analytical photo-centrifugal apparatus. The correlation between the PCR and oil droplet size prepared by emulsification at different pH and ionic strength media is discussed.
Fourteen novel silane coupling agents with a quaternary ammonium group introduced into the molecule, [CH2=CHCH2N+(CH3)(CnH2n+1)(CH2)3Si(OCH3)3]X- (n-X, n=10–18, X=Cl, Br, or I), were synthesized with the aim of using these agents to make material surfaces antimicrobial for a long period of time. Measurements of the minimum inhibitory concentrations (MIC) against 12 kinds of fungi and bacteria revealed that the coupling agent with a C10 alkyl chain and Cl- or Br- counter-ion (10-Cl or 10-Br) has the highest antimicrobial activity among the n-X agents synthesized, but 14-Cl and 14-Br showed the highest activity on a modified porcelain plate.
The photo-irradiation of thiobarbiturates (1) with an N-phenylalkyl group gives bicyclic fused pyrimidine derivatives (2) through a Norrish type II reaction. The crystal structures of dihydro-1,5,5-trimethyl-3-(3-phenylpropyl)-2-thioxo-4,6(1H,5H)-pyrimidinedione (1a) and the photocyclization product (2b) of dihydro-1,5,5-trimethyl-3-(3-phenylbutyl)-2-thioxo-4,6(1H,5H)-pyrimidinedione (1b) were elucidated by X-ray crystallographic analysis. The photocyclization product (2b) was determined to be 1,6,7,8-tetrahydro-1,3,3-trimethyl-9-phenyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione.
Commercially available conjugated linoleic acid (CLA) is a mixture of two main isomers. Fractionation of the two isomers was performed by a lipase-catalyzed esterification of CLA with L-menthol. In this study, a GC analytical method was developed to simultaneously determine the degree of esterification and fatty acid (FA) compositions of CLA in the free fatty acid (FFA) and ester forms without separation of the FFA and the ester. The methylation of the oil phase of the reaction mixture was performed using trimethylsilyldiazomethane in a mixture of toluene/methanol. Only FFA was quantitatively methylated, whereas the other compounds were little changed. A GC analysis using a polar column was performed to simultaneously determine the degree of esterification and the fatty acid compositions.