Lecithin Molar Ratio Research Articles

Robust sugar alcohol with lecithin functionalities for sustainable gelation of edible oils

Edible oleogels are of interest to many researchers in the food industry. However, the applications of oleogels in foods are limited owing to the demand for food-grade and low-cost gelators. In this study, we investigated a facile and reliable route for the formation of oleogels using lecithin and D-sorbitol as gelators, which are food-grade and commercially available. Grapeseed, olive, rice bran, and sesame oils are used as edible oils and all of which gel at a certain molar ratio of lecithin (40 mM) and D-sorbitol (42–54 mM), wherein the samples do not flow downward in the inverted vials and the formed oleogels are analyzed. The rheological properties of the samples, such as zero-shear viscosity (∼20 Pa.s to infinite viscosity), viscous modulus, and elastic modulus (70–110 Pa) under diverse conditions (i.e., shear-stress and temperature), were explored in detail by steady-shear and dynamic rheology. The mechanism of gel formation was also studied using small-angle X-ray scattering (SAXS) technique, which revealed that the gel was formed by the entanglement of the reverse cylindrical micelles (slop of I vs q: ∼1) induced by the hydrogen bonds between lecithin and D-sorbitol. Furthermore, the hydrogen bonds were confirmed with the Fourier transform infrared spectroscopy (FTIR), in which the absorbance bands of phosphate (red-shift) and carbonyl groups (blue-shift) of lecithin are shifted upon addition of D-sorbitol. Finally, this method to create oleogels of diverse edible oils using lecithin/D-sorbitol mixtures is simple and reproducible; thus, mass production of oleogels for marketable consumer products is expected to be achieved.

Self-assembly of micelles in organic solutions of lecithin and bile salt: Mesoscale computer simulation

We propose a coarse-grained model for studying the effects of adding bile salt to lecithin organosols by means of computer simulation. This model allows us to reveal the mechanisms of experimentally observed increasing of viscosity upon increasing the bile salt concentration. We show that increasing the bile salt to lecithin molar ratio induces the growth of elongated micelles of ellipsoidal and cylindrical shape due to incorporation of disklike bile salt molecules. These wormlike micelles can entangle into transient network displaying perceptible viscoelastic properties.

Preparation, characterization, and thermal stability of β-cyclodextrin/soybean lecithin inclusion complex

β-Cyclodextrin (β-CD), which is widely used to increase the stability, solubility, and bioavailability of guests, can form host–guest inclusion complexes with a wide variety of organic molecules. In this study the β-CD/soybean lecithin inclusion complex was prepared. The effect of reaction parameters such as reaction temperature, reaction time and the molar ratio of β-CD/soybean lecithin on inclusion ratio were studied. The inclusion ratio of the product prepared under the optimal conditions of β-CD/soybean lecithin molar ratio 2:1, reaction temperature 60°C reaction time 2h was 40.2%. The results of UV–vis, DSC, XRD and FT-IR spectrum indicated the formation of inclusion complex. The thermal stability experiment indicated that the thermal stability of soybean lecithin in inclusion complex was significantly improved compared with free soybean lecithin.

Enrichment of triglyceride docosahexanoic acid by lipase used as a hydrolysis medium in lecithin-based nano-scale molecular assemblage

Docosahexanoic acid (DHA) in triglyceride from marine bioresources was successfully enriched with the aid of lipase used for hydrolysis reaction in a water in oil (W/O) microemulsion formed by soybean lecithin. Ester-bonded DHA was hardly hydrolyzed by Candida rugosa lipase, due to their steric hindrance. In contrast, mono-unsaturated fatty acid in triglyceride was easily hydrolyzed by lipase specificity, and then it was removed. W/O microemulsion formed by soybean lecithin was used as an appropriate reaction medium for hydrophobic enzyme reaction. Soybean lecithin, well-known as a biocompatible amphiphile, was employed to prepare the W/O microemulsion. Phosphate buffer (6.0 ≦ pH ≦ 7.5) was used as an aqueous phase, and 2,2,4-trimethylpentane was employed as an organic solvent. The initial reaction rate obviously depended on the water–lecithin molar ratio, which was maximum at 10. The optimal lecithin concentration was 12 mM, which was almost the same level as the critical micelle concentration in the organic solvent. Soybean lecithin was superior to AOT in obtaining a higher initial reaction rate, due to moderate electrostatic interaction. The molar fraction of DHA in triglyceride was enriched up to 97%.

Effect of β-sitosterol concentration and high pressure homogenization on the chlorhexidine release from vesicular gels

Previous studies have confirmed that the phase transition of vesicular gels of hydrogenated phospholipids to the less ordered fluid vesicular state was induced by the increase of the β-sitosterol ratio in the whole gel system and consequently in the lipid bilayer. The purpose of the present study was to evaluate the influence of the β-sitosterol portion in the lipid bilayer and the effect of high pressure homogenization on the structural characteristics of the prepared gel systems. In addition the influence of β-sitosterol on the consequent chlorhexidine release from the obtained vesicles and liposomes was also examined. Lipid mixtures were prepared from different molar ratios of lecithin:sterol components (90:10–65:35 mol%). The obtained mixtures were hydrated with the aqueous solution of chlorhexidine digluconate in order to achieve a 30% (w/w) final concentration of the lipid mixtures and a 4% (w/w) concentration of the drug. One portion of the resultant multilamellar vesicles was homogenized by using high pressure. To characterize the homogenized and non-homogenized systems, transmission electron microscopy of the freeze-fractured samples and differential scanning calorimetry (DSC) were carried out. A vertical type diffusion cell was applied to determine the amount of released chlorhexidine digluconate. Along with the increase in β-sitosterol concentration, the fluidity of the membrane as well as its permeability also increased. The increased permeability—caused by the higher β-sitosterol concentration—and the high pressure homogenization, which increased the dispersity and therefore the surface area, enabled a higher amount of chlorhexidine to be released. The increase of drug release was more pronounced in the case of samples prepared with high pressure homogenization.

Localization and interactions of melatonin in dry cholesterol/lecithin mixed reversed micelles used as cell membrane models

The state of melatonin confined in dry cholesterol/lecithin mixed reversed micelles dispersed in CCl4 was investigated using 1H-NMR and FT-IR spectroscopies as a function of the melatonin to lecithin molar ratio (R(MLT)) and of the cholesterol to lecithin molar ratio (R(CHL)). An analysis of experimental results leads to the hypothesis that, independent of R(MLT) and as a consequence of anisotropic melatonin/lecithin, melatonin/cholesterol and cholesterol/lecithin interactions, melatonin is totally solubilized in reversed micelles. Melatonin is mainly located in and oriented in the nanodomain constituted by the hydrophilic groups of cholesterol and lecithin. A competition of melatonin and cholesterol for the hydrophilic binding sites of the reversed micelles was observed by changing the R(CHL). Some possible biological implications of the specific interactions governing the solubilization process, the preferential location and the peculiar properties of melatonin confined in cholesterol/lecithin mixed reversed micelles are discussed.

Effect of β-sitosterol on the characteristics of vesicular gels containing chlorhexidine

Previous studies confirm that β-sitosterol is very effective in altering the molecular packing of soybean lecithin bilayers even more than the cholesterol. The primary aim of the present study was to evaluate the influence of the β-sitosterol portion in the lipid bilayer on the physical–chemical characteristics of the prepared gel systems, and its influence on the consequent drug release from the liposomes obtained from vesicular phospholipid gels (VPG-s) by redispersion. VPG-s were prepared of different molar ratios of lecithin:sterol components (10:90–35:65 mol%). The mixture was hydrated with the aqueous solution of chlorhexidin digluconate in order to achieve 30% (w/w) final concentration of the lipid mixtures and 4% (w/w) concentration of the drug in each homogenized VPG sample. To characterize the obtained VPG systems optical microscopic examinations using polarized light, differential scanning calorimetry (DSC), photon correlation spectroscopy (PCS), and dynamic surface tension measurements were carried out. Vertical type diffusion cell was applied to determine the amount of released chlorhexidine digluconate. As a result of the surface tension-decreasing effect of β-sitosterol, the membrane deformability and the dispersity of the system increased. The increased dispersity and fluidity significantly increased the extent of released chlorhexidine from the vesicles.

Estimation of the Taurocholate to Lecithin Molar Ratio of Mixed Micelles in Taurocholate-Lecithin Solutions by an Interaction Model and Laser Light-Scattering Measurements

The taurocholate (TC) to lecithin (L) molar ratio (K) and molecular weight of mixed TC-L micelles coexisting with simple TC micelles were determined by employing laser light-scattering measurement and an interaction model of mixed and simple micelles. When the nonmixed micellar taurocholate (NMTC) concentration was greater than 25 mM, the K value and molecular weight of mixed TC-L micelles were ∼ 4.3 and ∼ 20,000 daltons, respectively, at an L concentration of 6 mM, and ∼ 2.0 and ∼ 35,000 daltons at L concentrations of 12 mM and 21 mM. A quantitative model of the formation of simple TC micelles and mixed TC-L micelles indicated that, when the NMTC concentration was greater than 25 mM, mixed TC-L micelles were unstable at low L levels because of low concentrations of L monomers.

In-vitro release of diclofenac diethylammonium from lipid-based formulations

This article presents the preparation and topical performance of some new lipid-based formulations of diclofenac, namely (a) a diclofenac aqueous gel containing mixed micelles (sodium cholate:egg lecithin molar ratio 0.55); (b) diclofenac lotion that contains soya lecithin, ethanol and buffer; and (c) diclofenac lipogel containing egg lecithin, isopropyl myristate, propylene glycol and ethanol. Gel formulations were prepared using Carbomer 934. Release of diclofenac from all formulations was monitored via dialysis through Spectra/por membrane into phosphate buffer (0.2 M pH=7.4) using a Franz cell. Drug release profile and diffusion coefficients were compared with brand formulation (Geigy's Vlotaren Emulgel). Statistical analysis of data show that the diffusion coefficient of the drug from these formulations rank according to the following order: Diclofenac lotion ( D=5.308×10 −7 cm 2/s) >lipogel ( D=2.102×10 −7 cm 2/s) >Voltaren Emulgel (1.518×10 −7 cm 2/s) >aqueous gel mixed micelle (0.966×10 −7 cm 2/s). These results show that diclofenac lotion and lipogel maybe more suitable formulations than the conventional topical dosage form.

Water Diffusion in Polymer-like Reverse Micelles. 2. Composition Dependence

A pulsed field gradient FT 1H NMR study on the system soybean lecithin/water/perdeuterated cyclohexane, covering a wide range of compositions, is presented. The water diffusion was found to be Gaussian with a well-defined, time-independent, single diffusion coefficient. After the contribution from the diffusion of water dissolved in the cyclohexane has been properly taken into account, all the data follow the same master curve as a function of the water to lecithin molar ratio (W0). The dominating mechanism for the water diffusion was found to be the motion inside giant wormlike reverse aggregates mediated by an interaggregates exchange with a characteristic time on the order of microseconds. For all the lecithin concentrations investigated, increasing the value of W0 increases the water diffusion up to W0 = 15, where a structural transition toward spherical aggregates causes a decrease in the water diffusion.

Structural characterization of the micelle-vesicle transition in lecithin-bile salt solutions

Small-angle neutron scattering (SANS) and dynamic light scattering (QLS) are used to characterize the aggregates found upon dilution of mixed lecithin-bile salt micelles. Molar ratios of lecithin (L) to taurocholate (TC) studied varied from 0.1 to 1, and one series contained cholesterol (Ch). Mixed aggregates of L and taurodeoxycholate (TDC) at ratios of 0.4 and 1 were also examined. In all cases the micelles are cylindrical or globular and elongate upon dilution. The radius of the mixed micelles varies only slightly with the overall composition of lecithin and bile salt which indicates that the composition of the cylindrical micelle body is nearly constant. The transition from micelles to vesicles is a smooth transformation involving a region where micelles and vesicles coexist. SANS measurements are more sensitive to the presence of two aggregate populations than QLS. Beyond the coexistence region the vesicle size and degree of polydispersity decrease with dilution. Incorporation of a small amount of cholesterol in the lipid mixture does not affect the sequence of observed aggregate structures.

Comparison of perturbation effect of propranolol, verapamil, chlorpromazine and carbisocaine on lecithin liposomes and brain total lipid liposomes. an EPR spectroscopy study

Effect of verapamil, propranolol, chlorpromazine and carbisocaine on dynamics and/or order of liposomes (perturbation effect), prepared from different molar ratios of lecithin (PC) and rat brain total lipids (TL) was studied by EPR spectroscopy using spin probes 16-doxyl stearic acid and 14-doxyl phosphatidylcholine. The PC liposomes had higher dynamics and/or lower order than the TL liposomes. The perturbation effect of the drugs depended largely on the lipid composition of the liposomes. The drugs at the drug/lipid molar ratios from 0.1 to 1 increased membrane dynamics and/or decreased membrane order. The drugs had the most pronounced perturbation effect in the liposomes prepared from brain total lipids. The effect of the drugs decreased with decreasing the TL PC ratio in the liposomes and was lowest, almost diminished, in the PC liposomes. Increasing concentration of the drugs decreased the difference between the dynamics and/or order of the PC and TL liposomes and so eliminated the influence of lipid composition on these membrane parameters. The results emphasize the role of lipid composition in studies concerning drug-lipid interactions in model and biological membranes.

Shear aligned lecithin reverse micelles: a small-angle neutron scattering study of the anomalous water-induced micellar growth

We present results from a small-angle neutron scattering study of shear-aligned viscoelastic reverse micellar solutions of lecithin in isooctane. We obtain direct evidence for the presence of cylindrical reverse micelles and a water-induced anisotropic growth in these solutions. A substantial increase of the micellar contour length L with increasing water to lecithin molar ratio w 0 can be observed

Simple micelle—mixed micelle coexistence equilibria for the taurocholate—, taurochenodeoxycholate—, and tauroursodeoxycholate—lecithin systems

A mapping of the simple micelle—mixed micelle coexistence behavior at 37°C and 0.1 M NaCl involving over 150 runs has been completed for the taurocholate—, taurochenodeoxycholate—, and tauroursodeoxycholate—lecithin systems. The equilibrium dialysis method was employed and equilibration times of the order of 100 to 150 h were required. For the taurocholate—lecithin and the taurochenodeoxycholate—lecithin systems, there was a significant transfer of lecithin across the membranes during the runs and a suitable correction procedure was adopted and validated. Negligible lecithin was transported across the same dialysis membranes in the tauroursodeoxycholate—lecithin experiments. From the simple micelle and the mixed micelle concentrations K, the bile salt-to—lecithin molar ratio for the mixed micelle was calculated. The K values were nearly constant and slowly decreasing for all three bile salt—lecithin systems with increasing lecithin concentration when lecithin levels were greater than 15 m M and when the NMBS (the nonmixed micelle bile salt) levels were greater than around 20 m M. At low NMBS levels, i.e., as the critical micelle concentration for the bile salt was approached, the K values decreased rapidly to low values. These studies have established a general methodology for investigating various factors which influence the coexistence behavior of bile salt—lecithin systems and, more specifically, provide a data base for the systematic examination of the dissolution kinetics behavior of cholesterol in bile salt—lecithin solutions.

A fluorescence study of the ternary system lecithin-sodium deoxycholate-water showing structural transformations

A fluorescence method was applied to study structural transitions occurring in the ternary system lecithinsodium deoxycholate-water. The method is based on binding of the hydrophilic probe rhodamine-B to the structures at molar ratios of lecithin and deoxycholate ( L/D) ranging from 0.16 to 10.7. The relationship between the fluorescence intensity and L/D ratio was sharply altered at molar ratios of 0.9 and 4.5. Thus three L/D regions could be distinguished and inflection points were estimated for each one. It is suggested that the L/D values of the sharp transitions (0.9 and 4.5) and the inflection points (0.5, 1.5 and 5.5) indicate generation of new types of molecular arrangements in the ternary system.

Structural dimorphism of bile salt/lecithin mixed micelles. A possible regulatory mechanism for cholesterol solubility in bile? X-ray structure analysis.

The three-dimensional structure of bile salt/lecithin mixed micelles in 0.15 M saline was derived from X-ray small-angle scattering measurements under various conditions. Two essentially different types of micelles were detected. At bile salt:lecithin molar ratios lower than approximately 2:1, lamellar particles similar to a lecithin bilayer arrangement were found. The thickness of the bilayer is 5.1 nm for mixed micelles having a molar ratio of 1:1. The lateral dimensions of the micelle were found strongly dependent upon molar ratio, increasing as lecithin content increases. In addition, it appeared that under certain incompletely defined conditions vesicular particles having diameters in the region of more than 100 nm occur. A molecular model of this type of micelle has been derived by means of a thorough interpretation of the electron density distribution across the plane of the bilayer. This model is generally consistent with the "mixed-disk" model of Mazer et al. [Mazer, N. A., Kwasnick, R. F., Carey, M. C., & Benedek, G. B. (1977) Micellization, Solubilization, Microemulsions, Proc. Int. Symp. 1, 383-402] and thus differs from that proposed by Small [Small, D. M. (1967) Gastroenterology 52,607-610] and Dervichian [Dervichian, D. G. (1968) Adv. Chem. Ser. No. 84, 78-87]. At molar ratios exceeding 2:1, a different type of micelle structure was found. This is a highly isometrical particle of globular shape, probably having a centrosymmetric arrangement of the molecular constituents. At a 3:1 bile salt:lecithin molar ratio, the mean physiological ratio for human gallbladder bile, the diameter of this micelle is 6.2 nm. Provided that other bile constituents have no significant influence on the structure, it may reasonably be expected that native gallbladder bile contains micelles of this latter type. The prevalent balance between the two micellar forms may thus regulate the capacity of bile to transport cholesterol.

Dimorphism in bile salt/lecithin mixed micelles.

We investigated the dependence of certain properties of bile salt/lecithin mixed micelles on the molar ratio of the two components. UV absorption suggested that the micellar system is fundamentally altered on passing through a bile salt:lecithin molar ratio of 1.8:1. Differential scanning calorimetry confirmed this transition ratio; in addition, it indicated a bilayer arrangement of lecithin, in support of the mixed-disk model of micellar structure, but only for micelles having a molar ratio less than 1.8:1. For micelles having larger ratios, which are those of physiological interest, calorimetry was inconsistent with the mixed-disk model. These observations support the X-ray structure analysis of Müller.

PROPERTIES OF CHLOROPH'YLL‐LECITHIN VESICLES: ULTRACENTRIFUGATION, ABSORBANCE, EMISSION AND PHOTOBLEACHING

Abstract— Egg lecithin vesicles (liposomes) containing up to one Chl a per 11 lecithin molecules were prepared without sonication. Their absorbance and emission properties indicate that Chl is dispersed in the lecithin, that the vesicles are dispersed in the medium and that there is a strong quenching of fluorescence.Their photobleaching and chemical bleaching show that there is a negligible amount of colloidal Chl present. In vesicles with a Chl:lecithin molar ratio higher than 0.05, there are probably some small aggregates of Chl a in the bilayer.The ultracentrifugation of such vesicles shows that their sedimentation constant increases, though not regularly, with their relative Chl content

The Incorporation of Steroid Molecules into Lecithin Sols, β‐Lipoproteins and Cellular Membranes

The dispersion of various steroids in aqueous solution with ovolecithin was investigated and the following molar ratios of lecithin to steroid obtained: cholesterol, 1:1; 7‐dehydrocholesterol, 13.3:1; ergosterol, 13.1:1; sitosterol, 2.0:1; sterophenol 4.2:1; cholesta‐4,6‐dien‐3‐one, 2.0:1; cholest‐4‐en‐3‐one, 1.7:1. The cholesterol contents of sterol‐depleted cellular membranes can be restored to their original level by incubation with plasma or an equimolar dispersion of cholesterol and ovolecithin, in the presence of 10% dimethylsulphoxide (v/v). Cholesta‐4,6‐dien‐3‐one, cholest‐4‐en‐3‐one, 7‐dehydrocholesterol and sterophenol can exchange readily with the cholesterol erythrocyte ghosts and can replace cholesterol molecules removed from the membrane. Ergosterol can do so only to a very limited extent. 7‐Dehydrocholesterol exchanges between rat erythrocyte ghosts and human piasma β‐lipo‐proteins in the same way as cholesterol. Cholesta‐4, 6‐dien‐3‐one and cholest‐4‐en‐3‐one also exchange but, in addition, there is a net uptake of these steroids by β‐lipoproteins. The extra steroid entering the lipoproteins is probably dissolved in the hydrophobic core of the latter. The exchange of cholesta‐4,6‐dien‐3‐one between erythocyte ghosts and lecithin/steroid dispersions or β‐lipoproteins is much more rapid than that of cholesterol. The rate of exchange of the dienone, like that of cholesterol, is increased by the addition of a small quantity of dismethylsulphoxide to the medium.