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PubMedDate not supplied

Chitosan-cholesterol and chitosan-stearic acid interactions at the air-water interface.

We report in this work the isotherms of cholesterol and stearic acid at the air-water interface modified by different chitosans (chitosan chloride, hydrophobic modified chitosan, and medium and high molecular weight chitosans) in the aqueous subphase. The Langmuir-Blodgett films of the complexes cholesterol-chitosan and stearic acid-chitosan are analyzed by atomic force microscopy (AFM), and a molecular simulation was performed to visualize the chitosan-lipid interactions. Strong modifications are obtained in the isotherms as a result of the chitosan interactions with cholesterol and stearic acid at the air-water interface. These modifications were dependent on the type and concentration of chitosan. Severe modifications of all phases were noticed with larger molecular areas, and the observed changes in the compressional modulus were dependent on the type of chitosan used. The complexes of chitosan-stearic acid were more flexible than the ones of chitosan-cholesterol. The AFM images demonstrated that chitosan was disaggregated by the cholesterol and stearic acid interactions producing more homogeneous surfaces in some cases. The hydrophobic chitosan showed more affinity with stearic acid, while both medium and high molecular weight chitosans produced homogeneous surfaces with cholesterol. The simulated chitosan chains interacting with cholesterol and stearic acid demonstrated the possibility of specific sites of electrostatic bonds between these molecules. Adsorption of cholesterol on the different powdered chitosans, performed by HPLC, showed that the medium and high molecular weight chitosans could retain higher proportions of cholesterol compared with the other analyzed samples.

Adsorption↗
PubMed1976

Model membrane studies of spin-label probes. Part 1. Mixed monolayers of 12-nitroxide stearic acid and myristic acid.

Pure and mixed monomolecular films of a cell membrane spin label probe, 12-nitroxide stearic acid have been studied where myristic acid was selected as the host lipid. The behavior of 12-nitroxide stearic acid at the air water interface is understood in terms of two molecular configurations: erect (with only the carboxyl group in the interface) and bent (with both the carboxyl group and the oxazolidine ring in the interface). In mixed films both of these conformations play a role at high surface pressures. At low probe concentrations, 12-nitroxide stearic acid is primarily in an erect conformation, while at high probe concentrations the reverse is true. This particular host lipid appears capable of erecting the probe molecule with only small concentrations of myristic acid. In a condensed host lipid, the probe is partially immiscible, and segregates to form a heterogeneous film from which it is readily collapsed. The probe is seen to perturb the molecular packing in this mixed system and the perturbation to be dependent on both the molecular shape and nature of the probe.

Binding Sites↗
PubMed1992

Prognostic significance of tumor phosphatidylcholine stearic acid level in breast carcinoma.

The involvement of lipid enzymes in the action of oncogenes at the cell membrane level has suggested that membrane lipids could play a role in modulating the growth of tumors. We previously found that breast cancer patients with a low level of polyunsaturated fatty acids in their primary tumor's phosphatidylethanolamine had a high risk of early occurrence of visceral metastasis. In the present study, we prospectively examined whether fatty acid composition of tumor membrane phosphatidylcholine had a prognostic significance in a series of 63 patients with a localized presentation of breast cancer. Membrane phospholipids were extracted from the carcinoma tissue obtained at the time of surgery, phosphatidylcholine was purified, and its fatty acids were analyzed by capillary gas chromatography. During the follow-up period, 20 patients developed metastasis. In these patients, the proportion of stearic acid containing phosphatidylcholine was significantly lower than it was in the tumors of the 43 patients who remained metastasis-free. Multivariate analysis according to Cox showed that low stearic acid level in tumor phosphatidylcholine and high mitotic index were independently predictive of subsequent metastasis. The predictive value of stearic acid level on metastasis risk was higher in node-positive patients than in node-negative patients, allowing individualization of a subgroup of low stearic acid level, node-positive patients with very poor prognosis. We concluded that stearic acid level in tumor membrane phosphatidylcholine is an independent intra-tumor marker of breast cancer prognosis. This finding is new evidence that tumor's structural lipids are linked to the growth of breast cancer.

Adult↗
PubMed2000

Dietary stearic acid reduces cholesterol absorption and increases endogenous cholesterol excretion in hamsters fed cereal-based diets.

The observation that dietary stearic acid does not raise plasma cholesterol concentration is well documented, although the regulating mechanisms are not completely understood. Therefore, we examined the effect of dietary stearic acid on cholesterol absorption and sterol balance using male Syrian hamsters fed modified NIH-07 cereal-based diets selectively enriched in palmitic acid (16:0), stearic acid (18:0), trans fatty acid (18:1t), cis oleic acid (18:1c) or linoleic acid (18:2). All diets contained 17 g/100 g total fat and 0.05 g/100 g cholesterol; the five fat blends were enriched 30% with the fatty acid of interest above a constant fatty acid background. Cholesterol absorption efficiency was 50-55% in all treatment groups except for the 18:0 group, in which cholesterol absorption was significantly reduced to 21%. Plasma total cholesterol concentration was significantly lower in the 18:0 group compared to the 16:0 group. Fecal neutral steroid excretion was significantly greater in hamsters fed the high 18:0 diet compared to the other treatment groups. After accounting for unabsorbed dietary cholesterol, endogenous cholesterol excretion was about 100% higher in the 18:0 group. Consequently, the calculated rate of whole body cholesterol synthesis was significantly increased by dietary 18:0. Bile acid excretion accounted for only 12-20% of total sterol output by the hamsters in this study. Thus, the data suggest that reduced plasma cholesterol concentration in hamsters fed high 18:0 diets may be influenced by reduced cholesterol absorption and increased excretion of endogenous cholesterol.

Analysis of Variance↗
PubMed1986

Stearic acid desaturation in rat liver microsomes: stimulation by fatty acid binding protein.

A soluble protein (Mr = 12,000) showing the characteristics of fatty acid binding protein is partially purified from rat liver cytosol (15-fold on the basis of its affinity for oleic acid) using ammonium sulphate precipitation. More oleate than stearate is removed from liver microsomes incubated with similar amounts of both fatty acids and the protein, indicating that it has a higher affinity for oleic than for stearic acid. When added to microsomes, a fraction enriched in this protein stimulates stearic acid desaturation. Such an effect is abolished if the protein is pre-saturated with oleic acid. It is suggested that the stimulation of stearic acid desaturation by fatty acid binding protein may involve a selective removal of the product, oleic acid, from the microsomal membranes.

Animals↗
PubMed2005

Effects of stearic acid on plasma lipid and lipoproteins in humans.

More than 40 years ago, saturated FA with 12, 14, and 16 carbon atoms (lauric acid, myristic acid, and palmitic acid) were demonstrated to be "hypercholesterolemic saturated FA". It was further concluded that the serum total cholesterol level would hardly be changed by isocaloric replacement of stearic acid (18:0) by oleic acid (cis-18:1n-9) or carbohydrates. These earlier studies did not address the effects of the various FA on the serum lipoprotein profile. Later studies found that the hypercholesterolemic saturated FA increase serum total cholesterol levels by raising concentrations of both the atherogenic LDL and the antiatherogenic HDL. Consequently, the ratio of total to HDL cholesterol will hardly change when carbohydrates replace these saturated FA. Compared with other saturated FA, stearic acid lowers LDL cholesterol. Studies on the effects on HDL cholesterol are less conclusive. In some, the effects on HDL cholesterol were comparable to those of palmitic acid, oleic acid, and linoleic acid, whereas in others a decrease was observed. This may suggest that in this respect the source of stearic acid is of importance, which needs however further study. From all these studies, however, it can be concluded that stearic acid may decrease the ratio of total to HDL cholesterol slightly when compared with palmitic or myristic acid. Without doubt, the effects of stearic acid are more favorable than those of trans monounsaturated FA.

Cholesterol, HDL↗
PubMed1990

Erythrocyte membrane stearic acid: oleic acid ratios in colorectal cancer using tube capillary column gas liquid chromatography.

Erythrocyte fatty acids were measured in 32 patients with colorectal cancer (four with recurrent disease), four patients with large colorectal adenomas, and 42 hospitalised patients without cancer. No significant differences were found with respect to any of the fatty acids between these groups. In particular there was no difference between the erythrocyte stearic acid: oleic acid ratios (mean +/- SD) between the cancer cases (1.07 +/- 0.31) and the control cases (1.09 +/- 0.31, 2-tailed Mann-Whitney U test). No difference in this ratio was observed with respect to age or sex and in the case of colorectal cancer, to the Dukes' stage, degree of tumour differentiation, or recurrence. A significant correlation was found between stearic acid concentrations in plasma and erythrocytes from fasting individuals (r = 0.477, n = 24, P less than 0.05). This study provides further evidence that the erythrocyte stearic acid: oleic acid ratio is of no value for diagnosing primary or recurrent colorectal cancer.

Aged↗
PubMed2003

TG containing stearic acid, synthesized from coconut oil, exhibit lipidemic effects in rats similar to those of cocoa butter.

Lipase-catalyzed interesterification was used to prepare structured TG from coconut oil TG by partially replacing some of the atherogenic saturated FA with stearic acid, which is known to have a neutral effect on lipid levels in the body. The level of stearic acid was increased from 4% in the native coconut oil to 40% in the structured lipids, with most of the stearic acid being incorporated into the sn-1 and sn-3 positions of TG. When structured lipids were fed to rats at a 10% level for a period of 60 d, a 15% decrease in total cholesterol and a 23% decrease in LDL cholesterol levels in the serum were observed when compared to those fed coconut oil. Similarly, the total and free cholesterol levels in the livers of the rats fed structured lipids were lowered by 31 and 36%, respectively, when compared to those fed coconut oil. The TG levels in the serum and in the liver showed decreases of 14 and 30%, respectively, in animals fed structured lipids. Rats fed cocoa butter and structured lipids having a similar amount of stearic acid had similar lipid levels in the serum and liver. These studies indicated that the atherogenic potential of coconut oil lipids can be reduced significantly by enriching them with stearic acid. This also changed the physical properties of coconut oil closer to those of cocoa butter as determined by DSC.

Animals↗
PubMed2005

[Preparation of stearic acid solid lipid nanoparticles containing podophyllotoxin].

OBJECTIVE: To improve the therapeutic efficacy and reduce the adverse effect of podophyllotoxin (PPT) by wrapping it in stearic acid solid lipid nanoparticles. METHODS: Stearic acid solid lipid nanoparticles containing podophyllotoxin was prepared using modified microemulsion technique, whose morphology was examined by transmission electron microscope. High-performance of liquid chromatography was employed to determine the entrapment efficiency of PPT in the nanoparticles. RESULT: The entrapment efficiency of PPT in the nanoparticles was 85.6% and the mean diameter of the particles was 56.5+/-25.8 nm. CONCLUSION: The stearic acid solid lipid nanoparticles has high entrapment efficiency for PPT and is homogeneous in size, which can be a promising targeted preparation for epidermal delivery.

Condylomata Acuminata↗
PubMed2004

Cd2+-induced interfacial structural changes of Langmuir-Blodgett films of stearic acid on solid substrates: a sum frequency generation study.

The molecular structures and their stabilities at the outmost-layer of the Langmuir-Blodgett (LB) films of stearic acid on solid substrates have been investigated by a highly surface-sensitive spectroscopic technique, sum frequency generation (SFG), in air and in aqueous solution, using the combination of both normal and deuterated stearic acid. Peaks observed in the SFG spectra are mainly attributed to the terminal methyl group at the outmost layer of the LB films. The SFG spectra in air are virtually identical and are independent of the odd-even property and thickness (1-12) of the LB films, indicating that the even-numbered LB film changes its surface structure after passing through the interface between the water subphase and air, especially when the Cd2+ cation was included in the water subphase. Furthermore, we have demonstrated for the first time using in situ SFG measurement that the interfacial molecular structure at the LB bilayer of stearic acid on the hydrophilic substrates significantly change with immersion in the water subphase containing Cd2+ cation while such a structural change has not been observed in the water subphase without Cd2+. These results clearly indicate that a reorganization process takes place on the surface of the stearic acid bilayer induced by the Cd2+ cation. The electrostatic interaction between the carboxylate headgroup of stearic acid via the Cd2+ cation seems to play an important role in the surface reorganization process both in air and in solution.

Journal Article↗
PubMed1994

Chocolate feeding studies: a novel approach for evaluating the plasma lipid effects of stearic acid.

Milk chocolate does not adversely affect plasma lipids and lipoproteins despite its relatively high content of saturated fatty acids (SFAs). Evidence from well-controlled feeding studies indicates that this unique response is due to the high proportion of stearic acid in milk chocolate. In experimental diets containing very high amounts (eg, 280 g/d, or 10 oz/d) and more typical amounts (46.2 g, or 1.65 oz) of milk chocolate, plasma total- and low-density-lipoprotein-cholesterol concentrations are not elevated. Furthermore, isoenergetic substitution of one milk chocolate bar per day for a high-carbohydrate snack in a National Cholesterol Education Program/American Heart Association Step 1 Diet does not adversely affect the cholesterol-lowering response. These findings indicate that stearic acid is not hypercholesterolemic as are the other long-chain SFAs. Thus, as illustrated by the different results generated from the predictive equations that group all long-chain SFAs vs those that consider stearic acid separately, grouping stearic acid with other SFAs appears to misrepresent the actual blood cholesterol response.

Adult↗
PubMed1979

In vivo incorporation of exogenous [1-14C]stearic acid into neurons and astrocytes.

Exogenous stearic acid is needed to synthesize the membranes of neurons and astrocytes. Subcutaneously injected [1-14C]acid is taken up through the 'blood brain barrier' and incorporated into lipids of both cell types, the specific radioactivity being higher in astrocytes as compared to neurons (2200 and 800 cpm/mg proteins, respectively), 20 h after injection. Phospholipids contain high amount of radioactivity (80% in astrocytes, 65% in neurons); glycosphingolipids contain low quantities of label in the two cell types. The injected acid is partly metabolized in the brain by elongation and desaturation (thus providing very long chains, saturated mono-unsaturated and poly-unsaturated); it is also partly degraded into acetate units (utilized for synthesis of palmitic acid).

Animals↗
PubMed1991

Effects of fats high in stearic acid on lipid and lipoprotein concentrations in men.

The effects of beef tallow and cocoa butter, two fats with a high stearic acid content (C18:0), on serum lipid and lipoprotein concentrations were compared with the effects of butter fat and olive oil in 10 middle-aged men. Liquid-formula diets containing 40% of the calories from the test fat were fed in random order for 3 wk each, with lipoprotein concentrations measured on the last five days. Butter fat raised low-density lipoprotein (LDL) concentrations the most (4.23 +/- .15 mmol/L; mean +/- SE). Beef-tallow feeding resulted in significantly lower concentrations of LDL (4.03 +/- 0.18 mmol/L); cocoa butter resulted in even lower concentrations (3.82 +/- .15 mmol/L). The lowest concentration of LDL was observed with olive oil (3.62 +/- 0.18 mmol/L). Fecal excretion of fatty acids, after adjustment for fecal flow, indicated that oleic acid (C18:1) was 99% absorbed, palmitic acid (C16:0) was 96-97% absorbed, and stearic acid was 90-94% absorbed for the three fats containing significant amounts of stearic acid.

Absorption↗
PubMed1988

Effects of sulfur-containing analogues of stearic acid on growth and fatty acid biosynthesis in the protozoan Crithidia fasciculata.

A variety of analogues of stearic acid in which one of the methylene groups was replaced by a sulfur atom were examined as inhibitors of growth and fatty acid biosynthesis in the trypanosomatid protozoan Crithidia fasciculata. The 8-, 9-, 10-, and 11-thiastearic acids were found to suppress the synthesis of the cyclopropane-containing fatty acid dihydrosterculic acid (9,10-methyleneoctadecanoic acid) at micromolar concentrations in the growth medium, and all but the 9-thiastearate were found to inhibit the growth of the protozoa at concentrations. The most potent inhibitor, 8-thiastearic acid (I50 for growth = 0.8 microM; I50 dihydrosterculate synthesis = 0.4 microM), was also observed to inhibit the synthesis of gamma-linolenic acid at a similar concentration. The sulfoxide derivatives of the 9- and 10-thiastearates were found to have little effect on growth or fatty acid synthesis, and several long-chain amides of 3-amino-1,2-propanediol were found to have effects similar to those of the fatty acids from which they were derived.

Animals↗
PubMed1999

Growth-modulating effects of dichloro myristic and dichloro stearic acid in cell cultures.

Chloro-containing fatty acids are a major fraction of extractable, organically bound chlorine in fish. It has been suggested that dichloro stearic acid (9,10-dichlorooctadecanoic acid) (C18) is metabolized to dichloro myristic acid (5,6-dichlorotetradecanoic acid) (C14) which accumulates in tissues. Hence, the biological effects of the C18 dichloro fatty acid could be due to formation of the C14 dichloro fatty acid. In this study we have compared the effects of dichloro stearic and dichloro myristic acid on growth of three widely differing cell lines. Both fatty acids inhibited cell growth; however, dichloro myristic acid had a weaker growth inhibitory effect than dichloro stearic acid. Dichloro myristic acid had a biphasic effect (i.e. growth was stimulated at low concentrations, followed by inhibition at higher concentrations) on the growth of human hepatoma cells and immortalized human kidney epithelial cells, but no such effect on human microvascular endothelial cells. The order of potency for growth inhibition by dichloro myristic acid was consistently human hepatoma cells>immortalized human kidney epithelial cells >human microvascular endothelial cells, whereas the relative potency of dichloro stearic acid was variable. Albumin alone stimulated cell growth and had a stronger protective effect against growth inhibition by dichloro myristic acid than against that of dichloro stearic acid. It seems unlikely that a major part of the effect of dichloro stearic acid on cell growth is caused by conversion to dichloro myristic acid.

Analysis of Variance↗
PubMed2006

Stearic acid solubility and cubic phase volume.

Stearic acid (SA) is highly soluble in structurally diverse solvents. SA/solvent packing within a (24.8 A)3 cubic volume explains the stoichiometry of SA solubility at multiple temperatures in multiple solvents. In the absence of solvent, the cubic volume contains 25 molecules at van der Waals distances from each other. At 55 degrees C, SA occupied half the cubic volume in saturated solution of four structurally diverse solvents. Below 4% SA/volume (e.g. in acetonitrile), the head and foot of each SA molecules on average is more than one solvent molecule away from the head and foot of a neighboring SA molecule. At 50% SA/cubic volume, -CH2- groups on SA molecules are separated from neighboring -CH2- groups on SA molecules by a monolayer of solvent molecules. Lowering the temperature from 55 to 25 degrees C, the volume fraction of SA decreased by a factor of 2 (or more) for every 6 degrees C. Lowering temperature increased the relative number of column of solvent molecules in the cubic phase, and correspondingly, the distance between SA molecules within the cubic volume increased. In three of five solvents, molecular mechanics calculations demonstrated the van der Waals stabilization that occurs from SA/SA affinity in the absence of solvent is similar in magnitude to the van der Waals stabilization from SA/solvent affinity. Methyl-t-butyl ether was less stabilized than hexane, acetone or methanol because the more bulky molecules packed less efficiently within the cubic volume. The most efficient/most stable packing however was still as columns of solvent between columns of SA. The efficiency and stability of SA and solvent packing optimal within the (24.8 A)3 cubic volume. Between 100 and 8% SA, multiple SA molecules present within the cubic volume function as SA aggregates. Both inter- and intra-cubic (phase) volume properties of SA aggregates coexist. Although acetonitrile and SA at the molecular level are both rod shaped, acetonitrile disrupted the packing of SA molecules within the cubic phase. The disrupted packing explains the much lower solubility of SA in acetonitrile than in the other solvents. The same molecular structures (e.g. methanol) can either stabilize or disrupt the packing of aggregated SA molecules, depending upon temperature. The mechanisms of aggregation within cubic volumes could also occur with structurally more complicated lipids. Aggregation and dispersion from such cubic phases could also be present in more complex chemical and/or macromolecular environments.

Acetone↗
PubMed2006

Novel self-aggregates of chitosan oligosaccharide grafted stearic acid: preparation, characterization and protein association.

A novel hydrophobically modified chitosan oligosaccharide (CSO) containing 5.4 stearic acid (SA) groups per 100 anhydroglucose units was synthesized by an 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated coupling reaction. The purified copolymer was structurally characterized by IR spectroscopy. Characteristics of self-aggregates of the amphiphilic copolymers were studied by fluorescence spectroscopy and dynamic light scattering. The critical aggregation concentration (cac) value of the self-aggregates in aqueous solution was determined by measuring the fluorescence intensity of pyrene as a fluorescent probe. Mean diameter of self-aggregates in pH 7.0 PBS was 25.0 +/- 14.7 nm with a unimodal size distribution. The diameter, as well as the zeta potential of self-aggregates increased when the pH value of dispersion medium decreased. Bovine serum albumin (BSA) was further enveloped in the interface of different single self-aggregate and formed nanoparticles. The size of BSA-loaded stearic acid modified CSO nanoparticles depended on the pH values of the dispersed aqueous vehicle, and the size diminished when the pH values of the dispersed aqueous vehicle decreased, whilst, the BSA encapsulation efficiency enhanced. The nanoparticles were characterized by Transmission Electron Microscopy (TEM). BSA release from stearic acid modified CSO nanoparticles decreased when the pH values of the delivery media decreased, in the range from 7.2 to 5.8.

Chitosan↗