Micellar Incorporation Research Articles

Comparative Evaluation of Micellization and Cellular Uptake of β-Carotene Affected by Flavonoids.

Based on in vitro digestion, micellar synthesis, and Caco-2 cell model, this study investigated the effects of typical flavonoids in citrus (naringenin, naringin, hesperetin, hesperidin, quercetin, and rutin) at different doses on the micellization and cellular uptake of β-carotene. In in vitro digestion, low-dose flavonoids enhanced β-carotene bioaccesssibility by regulating the stability and dispersibility of the intestinal medium, particularly quercetin, which significantly increased the bioaccessibility by 44.6% (p < 0.05). Furthermore, naringenin, hesperetin, hesperidin, and quercetin enhanced the micellar incorporation rate of β-carotene; however, naringin and rutin exhibited an opposite effect, particularly naringin, which significantly reduced it by 71.3% (p < 0.05). This phenomenon could be attributed to the high solubility of naringin and rutin in micelles, resulting in a competitive inhibitory effect on β-carotene. Besides, all treatments significantly enhanced β-carotene cellular uptake (p < 0.05) by promoting the expression of scavenger receptor class B type I and Niemann-Pick C1-Like 1.

Polymeric micelle gel with luliconazole: in vivo efficacy against cutaneous candidiasis in Wistar rats.

The objective of this research was focused on the design and development of luliconazole-loaded polymeric micelle hydrogel (LUL-PM-CHG) using quality by design (QbD) principle to improve the penetration and retention of LUL in the skin. The optimization of the formulation involved the utilization of a Box-Behnken design with three factors and three levels. The impact of specific formulation variables, namely the ratio of poloxamer P123 and F127, sonication time, and the quantity of drug, was investigated in terms of particle size, micellar incorporation efficiency, and polydispersity index. The LUL-loaded P123/F127 mixed micelles involved the thin film hydration method for thin preparation. The characteristics of optimized formulation include a particle size of 226 ± 8.52nm, a polydispersity index (PDI) of 0.153 ± 0.002, a zeta potential (ZP) of 30.15 ± 2.32mV, and a micellar incorporation efficiency (MIE) of 88.38 ± 3.84%. In vitro release studies indicated a sustained release of LUL-PM-CHG for a duration of up to 8h. The MIC, GI50, and GI90 of different formulations on Candida albicans were determined using both the microtiter broth dilution method and the plate method and showed that LUL-PM-CHG exhibited the highest antifungal activity compared to the other formulations, with MIC values of 3.25 ± 0.19ng/mL, GI50 values of 37.11 ± 2.89, and GI90 values of 94.98 ± 3.41 The study also measured the % of inhibition activity and the generation of intracellular reactive oxygen species (ROS) using flow cytometry. LUL-PM-CHG showed the highest percentage of inhibition (75.5%) and ROS production (MFI-140951), indicating its enhanced activity compared to LUL-CHG and LUL. Fungal infection was induced in Wistar rats using immunosuppressant's treatment followed by exposure to C. albicans. Finally, in vivo fungal scaling and histopathological studies indicated a reduction in fungal infection in Wistar rat skin after treatment. The obtained results suggested that LUL-PM can serve as a promising formulation to enhance luliconazole antifungal activity and increase patient compliance.

Specific Binding of Primary Ammoniums in Aqueous Media by Homooxacalixarenes Incorporated into Micelles.

The development of artificial receptors for efficient recognition of analytes in water is a challenging task. Homooxacalix[3]arene-based receptor 1, which is selective toward primary ammoniums in organic solvents, was transferred into water following two different strategies: direct solubilization and micellar incorporation. Extensive 1H NMR studies showed that recognition of ammoniums is only observed in the case of micellar incorporation, highlighting the beneficial effect of the microenvironment of the micellar core. The selectivity of the system for primary ammoniums over secondary and tertiary ones was also maintained. The hydrophobic effect plays an important role in the recognition properties, which are counterion-dependent due to the energy penalty for the dissociation of certain ammonium salts in the apolar micellar core. This study shows that the straightforward self-assembly process used for the encapsulation of artificial receptors in micelles is an efficient strategy for developing water-soluble nanosized supramolecular recognition systems.

Catalyst-free synthesis of phytosterol diacid monoesters and their competitive effect on the solubilization of cholesterol in model bile mixed micelles.

Phytosterols have received an extensive attention owing to their excellent cholesterol-lowering activity and the role in cardiovascular diseases prevention. Phytosterol diacid monoesters, the important intermediates in the structural modification of free phytosterols, were usually obtained by chemical method with catalyst. The aim of this research was to provide an eco-friendly approach for the preparation of phytosterol diacid monoester and explore the possible mechanism of their hypocholesteremic effect using model bile mixed micelles. Catalyst-free synthesis of β-sitosterol with succinic anhydride, maleic anhydride, and glutaric anhydride was investigated and optimized. The yields of three β-sitosterol diacid monoesters all reached above 94% under optimum reaction conditions and their chemical structures were confirmed further by mass spectroscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Compared with β-sitosterol, β-sitosterol diacid monoesters possessed the increased thermal stability (up to an above 355.28°C) and improved solubility in binary mixed micelle system (exceeding 1.7 mM) and similar cholesterol-lowering activity (7.78%-11.05%). Moreover, β-sitosterol diacid monoesters showed the competitive effect on solubilization of cholesterol due to their enhanced micellar incorporation capacity. Overall, the competition with cholesterol in vitro gives useful information about the cholesterol-lowering activity of phytosterol diacid monoesters, which will further expand their applications in the food industry and health. PRACTICAL APPLICATION: Modified phytosterols, phytosterol diacid monoesters, were successfully synthesized in petroleum ether without catalyst. These products enhanced the thermal stability of free phytosterols and reduced the dissolution capacity of cholesterol in model bile mixed micelles due to competitive solubilization. These results indicated that phytosterol diacid monoesters represented cholesterol-lowering potential, which might further expand the applications in the food industry and health.

Micellar Antibiotics of Bacillus.

Members of the Bacillus genus, particularly the “Bacillus subtilis group”, are known to produce amphipathic lipopeptides with biosurfactant activity. This includes the surfactins, fengycins and iturins that have been associated with antibacterial, antifungal, and anti-viral properties. We have screened a large collection of Bacillus, isolated from human, animal, estuarine water and soil samples and found that the most potent lipopeptide producers are members of the species Bacillus velezensis. B. velezensis lipopeptides exhibited anti-bacterial activity which was localised on the surface of both vegetative cells and spores. Interestingly, lipopeptide micelles (6–10 nm diameter) were detectable in strains exhibiting the highest levels of activity. Micelles were stable (heat and gastric stable) and shown to entrap other antimicrobials produced by the host bacterium (exampled here was the dipeptide antibiotic chlorotetaine). Commercially acquired lipopeptides did not exhibit similar levels of inhibitory activity and we suspect that micelle formation may relate to the particular isomeric forms produced by individual bacteria. Using naturally produced micelle formulations we demonstrated that they could entrap antimicrobial compounds (e.g., clindamycin, vancomycin and resveratrol). Micellar incorporation of antibiotics increased activity. Bacillus is a prolific producer of antimicrobials, and this phenomenon could be exploited naturally to augment antimicrobial activity. From an applied perspective, the ability to readily produce Bacillus micelles and formulate with drugs enables a possible strategy for enhanced drug delivery.

QbD based exploration of resveratrol loaded polymeric micelles based carbomer gel for topical treatment of plaque psoriasis: In vitro, ex vivo and in vivo studies

Topical delivery of Resveratrol is a safe method for treatment of plaque psoriasis which could overcome the existing limitations. However, poor permeability of biomolecules through the scaly and inflamed psoriatic skin is the major challenge to develop an effective and safe topical dosage form. Resveratrol loaded polymeric micelles of (PM) were developed using QbD based approach employing risk assessment and Central Composite Design to get optimized CMAs to achieve desired QTPP and CQAs (i.e. particle size, micellar incorporation efficiency, and skin deposition) which were obtained successfully. The optimized PM was converted into a gel (PMG) and evaluated for morphology and other physicochemical properties. It was also evaluated for ex vivo skin permeation and deposition ability, in vitro antioxidant activity, and in vivo efficacy using IMQ-induced psoriatic-like plaque model in mice. In vivo studies ratified the significant effectiveness of PMG as compared to conventional gel (CG). A significant reduction in PASI score, splenomegaly, serum cytokines levels, and hyperkeratosis in PMG treated group indicated superior utility of Resveratrol loaded PMG formulation. The present investigation ratifies QbD driven development of polymeric micelles which may be explored for better delivery of encapsulated cargos at the target site with enhanced therapeutic and dermatological benefits.

Cover Feature: Submerging a Biomimetic Metallo‐Receptor in Water for Molecular Recognition: Micellar Incorporation or Water Solubilization? A Case Study (Chem. Eur. J. 68/2018)

A poly(imidazole)–resorcinarene-based biomimetic receptor performs efficiently for Zn2+ coordination and anionic guest hosting when encapsulated in micelles or functionalized with water-solubilising groups. Despite very different microenvironments, binding constants and pH windows are strikingly similar; these results are related to the structuration of the receptor that mimics the active site of metalloenzymes. Micellar incorporation thus represents an easy alternative to difficult synthetic work, which opens many of perspectives for molecular recognition in water. More information can be found in the Full Paper by K. Bartik, O. Reinaud et al. on page 17964.

Submerging a Biomimetic Metallo-Receptor in Water for Molecular Recognition: Micellar Incorporation or Water Solubilization? A Case Study.

Molecular recognition in water is an important topic, but a challenging task due to the very competitive nature of the medium. The focus of this study is the comparison of two different strategies for the water solubilization of a biomimetic metallo-receptor based on a poly(imidazole) resorcinarene core. The first relies on a new synthetic path for the introduction of hydrophilic substituents on the receptor, at a remote distance from the coordination site. The second involves the incorporation of the organosoluble metallo-receptor into dodecylphosphocholine (DPC) micelles, which mimic the proteic surrounding of the active site of metallo-enzymes. The resorcinarene ligand can be transferred into water through both strategies, in which it binds ZnII over a wide pH window. Quite surprisingly, very similar metal ion affinities, pH responses, and recognition properties were observed with both strategies. The systems behave as remarkable receptors for small organic anions in water at near-physiological pH. These results show that, provided the biomimetic site is well structured and presents a recognition pocket, the micellar environment has very little impact on either metal ion binding or guest hosting. Hence, micellar incorporation represents an easy alternative to difficult synthetic work, even for the binding of charged species (metal cations or anions), which opens new perspectives for molecular recognition in water, whether for sensing, transport, or catalysis.

Formulation and in vivo assessment of terconazole-loaded polymeric mixed micelles enriched with Cremophor EL as dual functioning mediator for augmenting physical stability and skin delivery

The aim of the current study was to formulate terconazole (TCZ) loaded polymeric mixed micelles (PMMs) incorporating Cremophor EL as a stabilizer and a penetration enhancer. A 23 full factorial design was performed using Design-Expert® software for the optimization of the PMMs which were formulated using Pluronic P123 and Pluronic F127 together with Cremophor EL. To confirm the role of Cremophor EL, PMMs formulation lacking Cremophor EL was prepared for the purpose of comparison. Results showed that the optimal PMMs formulation (F7, where the ratio of total Pluronics to drug was 40:1, the weight ratio of Pluronic P123 to Pluronic F127 was 4:1, and the percentage of Cremophor EL in aqueous phase was 5%) had a high micellar incorporation efficiency (92.98 ± 0.40%) and a very small micellar size (33.23 ± 8.00 nm). Transmission electron microscopy revealed that PMMs possess spherical shape and good dispersibility. The optimal PMMs exhibited superior physical stability when compared with the PMMs formulation of the same composition but lacking Cremophor EL. Ex vivo studies demonstrated that the optimal PMMs formula markedly improved the dermal TCZ delivery compared to PMMs lacking Cremophor EL and TCZ suspension. In addition, it was found that the optimal PMMs exhibited a greater extent of TCZ deposition in the rat dorsal skin relative to TCZ suspension. Moreover, histopathological studies revealed the safety of the optimal PMMs upon topical application to rats. Consequently, PMMs enriched with Cremophor EL, as a stable nano-system, could be promising for the skin delivery of TCZ.

Carotenoid bioaccessibility and the relation to lipid digestion: A kinetic study

The micellar incorporation of carotenoids (lycopene, α- and β-carotene) and lipid digestion products (free fatty acids, FFAs, and monoacylglycerides, MAGs) during in vitro digestion of oil-in-water emulsions was investigated by a kinetic approach. A fractional conversion model could adequately describe the hydrolysis of triacylglycerides, formation of FFAs and MAGs, and micellar incorporation of carotenoids, FFAs and MAGs. The release of FFAs and MAGs from TAGs proceeded faster than their incorporation into micelles. Rate constants of carotenoid micellar incorporation were inversely proportional to their hydrophobicity and dependent on the isomeric configuration, being the incorporation of the cis faster than their all-trans isomers. Furthermore, a positive linear relation was found between the micellar incorporation of carotenoids and lipid digestion products. The isomeric form of carotenoids did not affect such relation. The present kinetic approach can be useful to gain mechanistic insight into carotenoid bioaccessibility as affected by various process- and product-related factors.

O‐Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

ABSTRACTThe nucleophilic reactivities of hydroxamate (HA−) ions of the structure RCONHO− [R = CH3 (acetohydroxamate, AHA−), C6H5 (benzohydroxamate, BHA−), 2‐OHC6H4 (salicylhydroxamate, SHA−), and 4‐CH3OC6H4 (4‐methoxbenzohydroxamate, MBHA−)] for the hydrolysis of p‐nitrophenyl benzoate (PNPB), tris(3‐nitrophenyl) phosphate (TRIS), and bis(2,4‐dinitrophenyl) phosphate (BDNPP) have been examined kinetically. Over the pH range of 6.7–11.4, the α‐nucleophile (HA−) accelerates deacylation of PNPB and dephosphorylation of TRIS (in cetyltrimethylammonium bromide (CTAB) micelle, 2.0 × 10−3 M). The salicylhydroxamate ion encountered effective catalysis than AHA−, BHA−, and MBHA− ions. The monoanionic SHA− and dianionic SA2− forms of salicylhydroxamic acid are the reactive species. The hydroxamic acid concentration–dependent critical micelle concentration (cmc) and fractional ionization constant (α) and of CTAB provide qualitative information for the micellar incorporation of the hydroxamate ion. The ab initio calculations performed on the hydroxamate ions at restricted Hartree–Fock using the 6‐311G (d,p) basis set revealed the O‐nucleophilicity of hydroxamate ions toward C=O and P=O centers. On the basis of ab initio calculation, it has been concluded that hydroxamic acids can exist into E‐amide and Z‐amide forms. The large stable amide or imide anions of hydroxamate are strong nucleophilic for the esterolytic cleavage of carboxylate and phosphate esters.

Paramagnetic Relaxation Enhancement Experiments: A Valuable Tool for the Characterization of Micellar Nanodevices

Micellar incorporation of hydrophobic molecular receptors is a promising strategy to obtain efficient nanodevices that work in water. In order to fully evaluate the potential of this approach, information on the localization and orientation of the receptor inside the micelle are necessary. Systematic studies undertaken on a uranyl-salophen receptor incorporated into CTABr and CTACl micelles show that nuclear magnetic resonance paramagnetic relaxation enhancement (NMR-PRE) experiments are particularly suitable to provide this type of information. The effect on the measurements of surfactant concentration, nature of the surfactant polar head, and ionic strength is also reported. Notably the normalization procedure applied to the obtained data can be considered of general application, thus enabling the comparison of information collected for different types of supramolecular micelle/receptor systems.

Design, optimization and in vitro evaluation of reverse micelle-loaded lipid nanocarriers containing erlotinib hydrochloride

Erlotinib hydrochloride (ERLO) belongs to the tyrosine kinase inhibitor family and is used for the treatment of pancreatic cancers. In the present study, ERLO was entrapped in lipid nanocarriers by means of reverse micellar incorporation. This study aims to optimize the formulation of ERLO-loaded nanoparticles. Surfactants forming reverse micelles in Labrafac(®) were filled with ERLO under various conditions. Both the initial amount of drug incubated with reverse micelles and the surfactant composing the reverse micelles are crucial parameters for reverse micelle capacity to load ERLO. The optimal loading system for reverse micelles was obtained with a mix of sorbitan trioleate (Span(®) 85) and Labrafac(®) oil at a 1:1 (w/w) ratio. Reverse micelle composition influenced the nanocarrier's hydrodynamic diameter, polydispersity index, and zeta potential. In lipid nanoparticles formulated by using the phase inversion temperature (PIT) method, ERLO entrapment efficiency was around 56%. In vitro, the efficacy of ERLO-loaded nanocarriers on BxPC-3 pancreatic adenocarcinoma cells was comparable to free ERLO, and led to a cell death rate of around 40%.

Preparation and pharmacokinetic evaluation of curcumin solid dispersion using Solutol® HS15 as a carrier

Solubility of curcumin at physiological pH was significantly increased by forming solid dispersion (SD) with Solutol® HS15. Since curcumin undergoes hydrolytic degradation, chemical stability study was conducted in pH 1.2, 6.8 and 7.4 buffer media. Solutol® HS15 exhibited superior stabilizing effect to Cremophor® RH40 and Kollidon® 30. The physical state of the dispersed curcumin in the polymer matrix was characterized by differential scanning calorimetry and X-ray diffraction studies. SD preparation transformed curcumin into amorphous form and facilitated micellar incorporation, thereby preventing hydrolysis in aqueous medium. In vitro drug release in pH 6.8 buffer revealed that SD (1:10) improved the dissolution of curcumin with approximately 90% release of the drug within 1h. Pharmacokinetic study of the solid dispersion formulation in rat showed that bioavailability of the drug was significantly improved as compared to pure curcumin. SD containing 1:10 ratio of drug and Solutol® HS15 resulted in approximately 5 fold higher AUC0–12h. SD formulation was physically stable over the study period of 3 months.

High Pressure Homogenization Increases the In Vitro Bioaccessibility of α‐ and β‐Carotene in Carrot Emulsions But Not of Lycopene in Tomato Emulsions

The correlation between food microstructure and in vitro bioaccessibility of carotenes was evaluated for tomato and carrot emulsions (5% olive oil) subjected to high pressure homogenization (HPH) at varying degrees of intensity. The aim was to investigate whether additional mechanical disruption of the food matrix could be utilized to further increase the carotene bioaccessibility of an already pre-processed material. The carotene bioaccessibility of the samples was measured after simulated in vitro digestion, carotene release to the oil phase was estimated by Confocal Raman spectroscopy and, to measure active uptake of carotenes, Caco-2 cells were incubated with the digesta of selected samples. HPH did not notably affect the retention of carotenes or ascorbic acid but significantly increased both the release and micellar incorporation of α- and β-carotene in carrot emulsions 1.5- to 1.6-fold. On the other hand, in vitro bioaccessibility of lycopene from tomato was not increased by HPH under any of the conditions investigated. Instead, the results suggested that lycopene bioaccessibility was limited by a combination of the low solubility of lycopene in dietary lipids and entrapment in the cellular network. Carotene uptake by Caco-2 cells appeared to be mainly dependent upon the carotene concentration of the digesta, but cis-trans isomerization had a significant impact on the micellarization efficiency of carotenes. We therefore conclude that HPH is an interesting option for increasing the bioaccessibility of carotenes from fruits and vegetables while maintaining a high nutrient content, but that the results will depend on both food source and type of carotene. A better understanding of the correlation between the processing of fruits and vegetables, microstructure and nutrient bioaccessibility can be directly applied in the production of food products with an increased nutritional value.

Phytosterols can impair vitamin D intestinal absorption in vitro and in mice

Adequate vitamin D status is necessary and beneficial for health, although deficiency and insufficiency are very common. As cholecalciferol (vitamin D(3) ) structure is close to cholesterol structure, we hypothesized that phytosterols, frequently used to decrease cholesterol, intestinal absorption and consequently to reduce hypercholesterolemia, may also interact with cholecalciferol absorption. β-Sitosterol effect on cholecalciferol postprandial response was first assessed in mice. We then evaluated the effect of different sterols on (i) cholecalciferol micellar incorporation, (ii) cholecalciferol apical uptake and (iii) basolateral efflux in vitro or ex vivo. In mice, cholecalciferol bioavailability was 15-fold lower in the presence of β-sitosterol (p<0.05). This can partly be explained by the fact that phytosterols significantly impaired cholecalciferol incorporation into mixed micelles (from -16 to -36% depending on sterol micellar composition). This can also be due to the fact that in Caco-2 cells and mouse intestinal explants, phytosterols significantly lowered cholecalciferol apical uptake (from -13 to -39%). Conversely, phytosterols had no effect on cholecalciferol secretion at the basolateral side of Caco-2 cells. The present data suggest for the first time that phytosterols can interact with vitamin D(3) intestinal absorption. This interaction can be explained by a competition for micellar incorporation and for apical uptake.

Nucleophilic Attack of Salicylhydroxamate Ion at C═O and P═O Centers in Cationic Micellar Media

The reaction between the salicylhydroxamate anion (SHA(-)) and p-nitrophenyl benzoate (PNPB), tris(3-nitrophenyl)phosphate (TRIS), and bis(2,4-dinitrophenyl)phosphate (BDNPP) have been examined kinetically. The α-nucleophile, SHA(-), incorporated into cetyltrimethylammonium bromide (CTAB) micelles accelerates dephosphorylation of tris(3-nitrophenyl)phosphate (TRIS) over the pH range 6.7-11.4. With a 1.0 mM of SHA in CTAB, the nucleophilicity of SHA followed the order of reactivity, PNPB (C=O, carboxylate ester) > TRIS (P=O, triester) > BDNPP (P=O, diester), and monoanionic SHA(-) and dianionic SA(2-) are the reactive species. The critical micelle concentration, cmc, of cetyltrimethylammonium bromide (CTAB) decreases and the fractional ionization constant, α, increases with increasing the concentration of SHA(-). Addition of 1 and 10 mM SHA under the reaction conditions (pH 9.2, borate buffer) led to saturation of the micellar surface and provided qualitative information for the micellar incorporation of hydroxamate ion. Plots of the pseudo-first-order rate constant, k(obs), log k(obs), fraction of hydroxamic acid ionized, α(SHA(-)) and α(SA(2-)), vs pH showed bifunctional nucleophilicity of hydroxamic acid under micellar condition. Plotting k(obs) vs [SHA](T) gave a straight line with intercept k(0). This indicates that hydroxamate ions are very strong nucleophiles for nucleophilic attack at the C and P center. The pseudo-first-order rate constant-surfactant profiles show micelle-assisted bimolecular reactions involving interfacial ion exchange between bulk aqueous media and micellar pseudophase.

Micellar lipid composition profoundly affects LXR-dependent cholesterol transport across CaCo2 cells

Intraluminal phospholipids affect micellar solubilization and absorption of cholesterol. We here study cholesterol transport from taurocholate–phospholipid–cholesterol micelles to CaCo2 cells, and associated effects on ABC-A1 mediated cholesterol efflux. Micellar incorporation of egg-yolk-phosphatidylcholine markedly increased apical retention of the sterol with decreased expression of ABC-A1, an effect that is prevented by synthetic liver X receptor (LXR) or retinoid X receptor (RXR) agonists. On the other hand, incorporation of lyso-phosphatidylcholine (LysoPC) increased ABC-A1–HDL-dependent basolateral cholesterol efflux, an effect that is abated when LXR is silenced. Thus, the modulation of cholesterol metabolism via intraluminal phospholipids is related to the activity of the oxysterol nuclear receptor LXR.

Changes in composition of the lipid matrix produce a differential incorporation of carotenoids in micelles. Interaction effect of cholesterol and oil

Abstract Efficiency of the micellar incorporation of carotenoids was determined through the application of an in vitro digestion procedure, and in function of the composition of the lipophilic environment, where digestion was carried out. Analysed factors affecting micellization level were presence of oil in the digestion mixture, class of pigment, and cholesterol. The addition of oil to the digestion mixture caused changes of different extent in function of the class of pigment, and significant interactions between the factors presence of oil and class of pigment were detected. Accessibility of lycopene was affected negatively by an increase of the amount of vegetable oil, while lutein ester increased its presence in micelles. Although cholesterol was not a significant factor affecting the micellization efficiency, when cholesterol and oil were added to the digestion process, the amount of micellarized pigment was significantly affected, positively or negatively depending on lipophilic characteristics of the pigment. Therefore, an interaction between the factors cholesterol and presence of oil with different effects on the micellization of pigments was analysed. The physical–chemical differences of carotenoids, that are consequence of their structural features, generated diverse requirements of the lipophilic environment to facilitate their emulsion and subsequent incorporation into micelles. Industrial relevance Carotenoid pigments are widely used by the food industry as colorants, although nutritional and functional properties make them to be applied for other purposes, as in the enhancement of functional foods. The physico-chemical characteristics of carotenoids make them to be low bioavailable, so that a correct formulation of the food matrix is required in order to achieve an appropriate bioavailability. The development of in vitro digestion methods, which allow the measurement of the potential bioavailability of carotenoids, could be considered as a useful tool to screen those factors and components that modify the bioavailability of these compounds in a given matrix composition so selection of the formulation conditions that gives the higher availability may be performed. The aim of this work was the development and application of an in vitro method to measure the potential bioavailability of carotenoids considering several factors that modulate it.

Reactions of p-Nitrophenyl Diphenyl Phosphinate with Fluoride and Hydroxide Ion in Nonionic Micelles: Kinetic Salt Effects

Reactions of p-nitrophenyl diphenyl phosphinate (p-NPDP) with OH− and F− are inhibited by micelles of dodecyl polyoxyethylene ethers C12E10 and C12E23. Rate constants decrease sharply in very dilute surfactant and become approximately constant as p-NPDP becomes fully micellar bound, with inhibition by approximately an order of magnitude. The first-formed fluoridate is detected by NMR spectroscopy in reaction with F− in DMSO-d6:D2O 85:15 v/v, but not in other conditions. Kinetic salt effects on the micellar reactions are ion specific. Bulky anions, ClO−4 and naphthalene-2-sulfonate ion (ONs−), inhibit reactions much more than small ions, and (C7H15)4N+ accelerates reaction of F−. Micellar incorporation of ONs− in the micelles is demonstrated by changes in 1H-NMR spectra of the surfactants. Comparison of rate constants of reaction of F− in PEG (MW 104) and in nonionic micelles shows that the micellar inhibition is due largely to lower ionic concentrations in the micelles than in water.