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We report herein the syntheses of several analogues of stearic acid in which oxygen or sulfur atoms or sulfoxide groups have replaced the methylene groups at either position 9 or position 10 of the polymethylene chains. These compounds have been fully characterized by the results of proton and carbon 13 nuclear magnetic resonance, and low and high resolution mass spectral studies.
Human serum albumin (HSA) has been spin-labelled with stearic acids having the nitroxide moiety attached to the hydrocarbon chain either at the 5th or at the 16th carbon atom (n-SASL, n = 5 and 16, respectively) with respect to the carboxyl groups. Its interaction with sterically stabilized liposomes (SSL) composed of dipalmitoylphosphatidylcholine (DPPC) mixed with submicellar content of poly(ethylene glycol:2000)-grafted dipalmitoyl phosphatidylethanolamine (PEG:2000-DPPE) has been studied by conventional electron spin resonance (ESR) spectroscopy. In the absence of bilayer membranes, the ESR spectra of nitroxide stearic acids non-covalently bound to HSA are single component powder patterns, indicative of spin labels undergoing temperature dependent anisotropic motion in the slow motional regime on the conventional ESR timescale. The adsorption of HSA to DPPC bilayers results in two component ESR spectra. Indeed, superimposed to an anisotropic protein-signal appears a more isotropic signal due to the labels in the lipid environment. This accounts for the transfer of fatty acids from the protein to DPPC bilayers. Two spectral components with different rotational mobility are also singled out in the spectra of n-SASL bound to HSA when DPPC/PEG:2000-DPPE mixtures are present in the dispersion medium. The fraction, f(L)(16-SASL), of spin labels transferred from the protein to lipid/polymer-lipid lamellar membranes has been quantified performing spectral subtraction. It is found that f(L)(16-SASL) decreases on increasing the content of the polymer-lipid mixed with DPPC. It is strongly reduced in the low-density mushroom regime and levels off in the high-density brush regime of the polymer-lipid content as a result of the steric stabilization exerted by the PEG-lipids. Moreover, the fraction of transferred fatty acids from HSA to SSL is dependent on the physical state of the lipid bilayers. It progressively increases with increasing the temperature from the gel to the liquid-crystalline lamellar phases of the mixed lipid/polymer-lipid membranes, although such a dependence is much weaker in the brush regime.
The effects of long chain fatty acids (LCFAs) on glucose degradation were examined at 21 degrees C. A competitive inhibition model was used to determine the kinetics of glucose degradation. Half velocity constants (Ks) were a function of LCFA concentration only at 100, 300 and 500 mg l(-1). The inhibitor constants (KI) for individual and mixed LCFAs were statistically the same. Glucose degradation rates for cultures receiving saturated (stearic acid (SA)) and monounsaturated (oleic acid (OA)) LCFAs were statistically the same but statistically different when compared to cultures fed with a polyunsaturated LCFA (linoleic acid (LA)). Individual and mixed LCFAs inhibited glucose degradation at threshold levels of 300 and 500 mg l(-1), respectively.
The adsorption of stearic acid and bis(2-ethylhexyl) phosphate, from toluene and THF solutions, on magnetic iron pigments (MP) was examined. Adsorption isotherms as well as the concomitant variations of surface electrical (zeta) potential were determined. The formation of electrical surface charges is explained by charge transfer processes between the solvents, the adsorbates, and MP. An adsorption competition is evidenced when contacting MP with the adsorbates using 14C-labeled stearic acid.
The effect of fats high in individual, prevalent saturated dietary fatty acids on lipoproteins and hemostatic variables in young healthy subjects was evaluated in a randomized strictly controlled metabolic feeding study. Three experimental diets: shea butter (S; 42% stearic acid), palm oil (P; 43% palmitic palmitic acid), and palm-kernel oil with high-oleic sunflower oil (ML; 10% myristic acid, 30% lauric acid) were served to 15 men for 3 wk each, separated by washout periods. Diet S compared with diet P resulted in significant reduction in plasma cholesterol (22%) LDL cholesterol (26%), apolipoprotein B (18%), HDL cholesterol (12%), apolipoprotein A-I (13%), and a 13% lower factor VII coagulant activity (P = 0.001). Similar differences were observed between diets S and ML. In conclusion, intake of shea butter high in stearic acid favorably affects blood lipids and factor VII coagulant activity in young men, compared with fats high in saturated fatty acids with 12-16 carbons.
The zeta (zeta) potential of an insoluble monolayer of stearic acid at the air-water interface was measured as a function of pH in the presence of 0.0001, 0.001, and 0.01 M NH4NO3. The zeta potential was measured by means of the plane interface technique which involved the determination of the electrophoretic velocity profile of reference (polystyrene latex) particles along the solution depth in a rectangular open quartz cell. The zeta vs pH relationship at 0.001 and 0.01 M NH4NO3 was analyzed in terms of the Gouy-Chapman-Stern-Grahame model for electrical double-layer incorporating a simple site-binding model used previously for many oxide and latex colloid studies. The dissociation constant (pKa) of stearic acid monolayer and double-layer parameters such as integral capacitances of inner and outer Helmholtz layers and the complexation constant of counterion complexes were also estimated.
Stearic acid desaturase activity was assayed in preparations from perigenital adipose tissue and liver from lean and genetically obese female mice (ob/ob). The total activity in the perigenital adipose tissue from obese mice was threefold greater than in the tissue from lean mice, but per g of adipose tissue the activity was twofold greater in tissue from lean mice. In liver, the activity in obese mice was elevated at 8 weeks of age, remained elevated up to 24 weeks and then decreased by half at 48 weeks, but at all ages was higher than that in lean mice. The decrease in desaturase activity of liver from obese mice at 48 weeks corresponded to a change in the fatty acid composition of liver lipids toward that found in lean mice. Whereas in adipose tissue much of the increased enzyme activity may be due to tissue hyperplasia, in liver it is mainly an increased activity per cell.
Structural analysis of Na-montmorillonite co-intercalated with octadecylamine and stearic acid was carried out using combination of experiment: X-ray powder diffraction and IR spectroscopy with molecular modeling (force field calculations) in Cerius(2) modeling environment. Results of structure analysis revealed the chemical reaction of guest compounds leading to the formation of octadecylammonium stearate. This reaction may occur even before the intercalation out of the interlayer space of montmorillonite. The presence of octadecylammonium stearate in the samples was clearly confirmed by IR spectroscopy and X-ray diffraction. Present results also showed that: (1) Stearic acid itself does not intercalate into Na-montmorillonite; (2) cointercalation with octadecylamine led to the formation of octadecylammonium stearate, which was successfully intercalated into the interlayer space of montmorillonite, and (3) Na-montmorillonite intercalated with octadecylammonium stearate does not create a stable structure. Intercalated samples in ambient conditions undergo gradual decomposition, accompanied by the release of octadecylammonium stearate from the interlayer space and rearrangement of the interlayer structure. Co-intercalation of STA and ODA to lower the octadecylamine content and consequently to suppress the unfavorable effect of amine groups on the polymer matrix in nanocomposite, was investigated.
Electron-electron double resonance (ELDOR) and saturation recovery electron paramagnetic resonance (EPR) spectroscopy have been employed to examine the interactions of 14N:15N stearic acid spin-label pairs in fluid-phase model membrane bilayers composed of a variety of phospholipids. The [14N]-16-doxylstearate:[15N]-16-doxylstearate (16:16) pair was utilized to measure lateral diffusion of the spin-labels, while the [14N]-16-doxylstearate:[15N]-5-doxylstearate (16:5) pair provided information on vertical fluctuations of the 16-doxylstearate nitroxide moiety toward the membrane surface. Three saturated host lipids of varying alkyl chain length [dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), and distearoylphosphatidylcholine (DSPC)], an alpha-saturated, beta-unsaturated lipid [1-palmitoyl-2-oleoylphosphatidylcholine (POPC)], and phosphatidylcholine from a natural source [egg yolk phosphatidylcholine (egg PC)] were utilized as host lipids. Lateral diffusion of the stearic acid spin-labels was only slightly affected by alkyl chain length at a given reduced temperature (Tr) in the saturated host lipids but was significantly decreased in POPC at the same Tr. Lateral diffusion in DMPC, POPC, and egg PC was quite similar at 37 degrees C. A strong correlation was noted between lateral diffusion constants and rotational mobility of [14N]-16-doxylstearate. Vertical fluctuations were likewise only slightly influenced by alkyl chain length but were strongly diminished in POPC and egg PC relative to the saturated systems. This diminution of the 16:5 interaction was observed even under conditions where no differences were discernible by conventional EPR. These studies indicate that vertical fluctuation of 16-doxylstearate is quite sensitive to host lipid unsaturation and that ELDOR studies of interactions between 14N:15N spin-label pairs can provide information on spin-label motion beyond that given by conventional EPR.
Two surface-active formulation ingredients, a water-soluble derivative of vitamin E (D-alpha-tocopherol polyethylene glycol 1000 succinate, vitamin E-TPGS) as well as a polyethoxylated derivative of 12-hydroxy-stearic acid (Solutol HS 15) were investigated in rats for their potential to increase the oral bioavailability of the p-glycoprotein (p-gp) and cytochrome P450 substrate colchicine. D-alpha-Tocopherol polyethylene glycol 1000 succinate and the polyethoxylated derivative of 12-hydroxy-stearic acid will be referred to as "surfactant 1" and "surfactant 2" in the following. Colchicine was administered to the animals at a dose level of 5 mg/kg in each 10% surfactant containing formulation. A solution of colchicine in isotonic saline was selected as a reference formulation. It was found that the administration of colchicine in the surfactant containing formulations resulted in significantly higher systemic exposures as compared to the aqueous reference vehicle (2-fold increase in AUC in the presence of surfactant 1 and 4-fold increase in AUC in the presence of surfactant 2). The aqueous solubility of colchicine was about 16.7 mg/ml, and the increase in solubility in the presence of 1% surfactant 1 or surfactant 2 to about 20.5 and 18.5 mg/ml was not considered to significantly affect the oral bioavailability. In summary, it was demonstrated that both surfactants are suitable formulation ingredients to improve the systemic exposure of colchicine in the rat. Due to the high aqueous solubility of colchicine the most likely reasons for these findings are inhibition of p-gp and/or metabolism as well as permeability enhancement by interactions of the surfactants with the intestinal membrane.
The aim of this study was to identify ruminal bacteria that form stearic acid (18 : 0) from linoleic acid (cis-9,cis-12-18 : 2). One 18 : 0-producing isolate, P-18, isolated from the sheep rumen was similar in morphology and metabolic properties to 'Fusocillus' spp. isolated many years ago. Phylogenetic analysis based on nearly full-length 16S rRNA gene sequence (>1300 bp) analysis indicated that the stearate producer was most closely related to Clostridium proteoclasticum B316(T). Clostridium proteoclasticum B316(T) was also found to form 18 : 0, as were other bacteria isolated elsewhere, which occurred in the same family subclass of the low G+C% Gram-positive bacteria, related to Butyrivibrio fibrisolvens. These bacteria are not clostridia, and the ability to form 18 : 0 was present in all strains in contrast to proteolytic activity, which was variable. Production of 18 : 0 occurred in growing, but not in stationary-phase, bacteria, which made detection of biohydrogenating activity difficult, because of the inhibitory effects of linoleic acid on growth.
Stearic acid (SA) grafted chitosan oligosaccharide (CSO) (CSO-SA), which was synthesized by an 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)-mediated coupling reaction, was demonstrated to form micelle like structure by self-aggregation in aqueous solution. The critical micelle concentration (CMC) of CSO-SA with 15.4% amino substituted degree of CSO was about 0.035 mg/ml. The micelles with 1mg/ml CSO-SA concentration had 70.6 nm volume average hydrodynamic diameter with a narrow size distribution and 46.4+/-0.1 mV surface potential. Due to the cationic property, the micelles could compact the plasmid DNA to form micelle/DNA complexes nanoparticles, which can efficiently protect the condensed DNA from enzymatic degradation by DNase I. The volume average hydrodynamic diameter of CSO-SA micelle/DNA complex increased from 203 nm to 318 nm and decreased to 102 nm due to the variation of zeta potential when the N/P ratio increased from 0.25 to 3.6 and from 3.6 to 58. The IC(50) value of the CSO-SA micelle against A549 cells was 543.16 microg/ml, while the IC(50) of Lipofectamine 2000 was about 6 microg/ml. The in vitro transfection efficiency of CSO-SA micelles was investigated by using plasmid DNA (pEGFP-C1). The transfection efficiency with CSO-SA/DNA (N/P ratio is 29) was increased with the post-transfection time (in 76h), while the optimal transfection of Lipofectamine 2000/DNA was obtained at 24h. The transfection of CSO-SA was not interfered in the presence of 10% fetal bovine serum, which showed remarkable enhancement effect. The optimal transfection efficiency of CSO-SA micelles in A549 cells was about 15%, which was higher than that of CSO (about 2%) and approach to that of Lipofectamine 2000 (about 20%). The low cytotoxic biodegradable CSO-SA micelles could be used as an effective DNA condensation carrier for gene delivery system.
Although there is general agreement that saturated fatty acids elevate plasma cholesterol concentrations, the relative effects of individual fatty acids on cholesterol and bile acid metabolism are less clear. In this study, cholesterol and bile acid responses to diets enriched in different saturated fatty acids were investigated in hamsters. The six diets examined were as follows: 5% fat (g/100 g) enriched in palmitic acid (16:0) with no cholesterol, 5% fat 16:0-enriched, 0.05% cholesterol (wt/wt), and four diets containing 0.05% cholesterol and 15% fat with each diet enriched in lauric (12:0), myristic (14:0), palmitic (16:0), or stearic acid (18:0). Total plasma cholesterol concentration was significantly greater in hamsters fed the 14:0-enriched diet relative to those fed the 18:0-enriched diet (P < 0.05). Both plasma and liver cholesterol concentrations of hamsters fed 18:0 did not differ from those of the group fed no dietary cholesterol. In all instances, differences in total plasma cholesterol were accounted for within the HDL fraction; no significant treatment differences in VLDL or LDL cholesterol were found. Total daily fecal bile acid excretion was higher in hamsters fed the 15% fat 16:0 diet compared with those fed no dietary cholesterol (P < 0.05), but not significantly different from other treatment groups. There was greater deoxycholic acid excretion (P < 0.05) from hamsters fed the 14:0 and 16:0 diets compared with those fed the 18:0-enriched diet. Small intestinal + gallbladder bile acids, an index of pool size, did not differ significantly among the groups. The observed relative hypocholesterolemic effect of stearic acid was not mediated by increased bile acid excretion.
The purpose of this study is to evaluate the possibility of developing a cylindrical sustained-release dosage form for theophylline directly by means of a ram extrusion process. In particular, the formulations contained: stearic acid as a low melting binder, monohydrate lactose and polyethylene glycol 6000 as hydrophilic fillers. The influence of type and percentage of the components was studied considering different parameters such as the time required for 50% of the drug release (t50%)and the drug diffusion coefficient in the delivery system. The choice of the different formulations to be tested is carried out employing an axial design with constraint domains. The limits of each component were fixed on the basis of preliminary trials. The analysis of the t50% values revealed that the release kinetics is mainly affected by stearic acid and theophylline content, whilst lactose effect is almost negligible. A substantial correspondence between the experimental results and the analysis of the drug release kinetics performed by means of an ad hoc developed mathematical model was found. The proposed mathematical model allows to conclude that wherever the release mechanism is initially ruled by dissolution, then diffusion plays the most important role.
While it is well established that the fatty acid composition of dietary fat is important in determining plasma lipoprotein cholesterol concentrations, the effects of changing the absolute quantities of the individual fatty acids are less clear. In the present study Golden Syrian hamsters were fed on isoenergetic, low cholesterol (0.05 g/kg) diets containing 100, 150 or 200 g added fat/kg. This consisted of triolein (TO) alone, or equal proportions of TO and either trimyristin (TM), tripalmitin (TP) or tristearin (TS). Each trial also included a control group fed on a diet containing 50 g TO/kg. As the mass of TO in the diet increased, plasma VLDL-cholesterol concentrations rose. The TM-rich diets produced a concentration-dependent increase in total plasma cholesterol which was a result of significant increases in both VLDL and HDL levels. The TP-rich diets increased plasma LDL- and HDL-cholesterol levels in a concentration-dependent manner. TS-containing diets did not increase the cholesterol content of any of the major lipoprotein fractions. Hepatic LDL-receptor mRNA concentrations were significantly decreased in animals fed on TP, while apolipoprotein B mRNA concentrations were significantly increased. Thus, on a low-cholesterol diet, increasing the absolute amount of dietary palmitic acid increases LDL-cholesterol more than either myristic or stearic acid. These effects on lipoprotein metabolism may be exerted through specific modulation of the expression of the LDL receptor and apolipoprotein B genes.
Mixed monolayers of stearic acid (SA) and octadecylamine (ODA) at the air/water interface were investigated in this article. The miscibility of the two compounds was evaluated by the measurement of surface pressure-area per molecule (pi-A) isothems and the direct observation of Brewster angle microscopy (BAM) on the water surface. The two compounds were spread individually on the subphase (method 1) or premixed first in the spreading solvent and then cospread (method 2). The effect of spreading method on the miscibility of the two compounds was also studied. The results show that the mixed monolayers prepared by method 1 cannot get a well-mixed state. The isotherms of mixed monolayers preserve both characteristics of SA and ODA and exhibit two collapse points. The calculated excess surface area is very small. Besides, distinguished domains corresponding to those of pure SA and ODA can be inspected from the BAM images. Such results indicate that SA and ODA cannot get a well-mixed phase via 2-dimensional mixing. On the contrary, in the mixed monolayer prepared by cospreading, the two compounds exhibit high miscibility. In the pi-A isotherms, the individual characteristics of SA and ODA disappear. The calculated excess area exhibits a highly positive deviation which indicates the existence of special interaction between the two compounds. The low compressibility of isotherm implies the highly rigid characteristic of the mixed monolayer. which was also sustained by the striplike collapse morphology observed from the BAM. The rigid characteristic of SA/ODA mixed monolayer was attributed to the formation of "catanionic surfactant" by electrostatic adsorption of headgroups of SA and ODA or to the formation of salt by acid-base reaction.
We studied liver microsomal delta 9 stearic acid desaturase activity and fatty acid composition of liver phospholipids and microsomal total lipids in the insulin-dependent spontaneously diabetic adult male Bio-Breeding rat. The diabetic Bio-Breeding rats (3 weeks of diabetes) were killed 48, 17 and 3 h after the last insulin injection (1.0 IU, 100 g body weight-1 day-1). Under these experimental conditions, delta 9 desaturase activity was defective during the normo- and hyper-glycaemic periods and restored during the hypoglycaemic period which followed the insulin injection to the diabetic rats. The fatty acid composition of diabetic rat liver phospholipids and microsomal total lipids were not consistent with delta 9 desaturase activity at the different periods of glycaemia and may be explained by factors other than disturbances of this desaturation.
Individual FA have diverse biological effects, some of which affect the risk of cardiovascular disease (CVD). In the context of food-based dietary guidance designed to reduce CVD risk, fat and FA recommendations focus on reducing saturated FA (SFA) and trans FA (TFA), and ensuring an adequate intake of unsaturated FA. Because stearic acid shares many physical properties with the other long-chain SFA but has different physiological effects, it is being evaluated as a substitute for TFA in food manufacturing. For stearic acid to become the primary replacement for TFA, it is essential that its physical properties and biological effects be well understood.