Carotenoid incorporation into natural membranes from artificial carriers: liposomes and β-cyclodextrins (original) (raw)
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Biochimica Et Biophysica Acta-general Subjects, 2000
A physiological, water-soluble complex of carotenoids with methyl-L-cyclodextrin (MLCD) was developed for the purpose of cell supplementation. Bioavailability, cytotoxicity and stability of the formulations were compared to carotenoid solutions in organic solvents (THF/DMSO (1:1), THF and ethanol). The stability of the different carotenoid solutions (0.5 WM) under cell culture conditions was determined by measuring absorbance 1 and 7 days after treatment. To determine the availability of L-carotene (BC), human skin fibroblasts were incubated for up to 8 days with 5 WM BC in MLCD or THF/DMSO and the cellular and medium BC contents were determined by HPLC analysis. Depending on the solubilizer, different orders of stability were found. MLCD formulation: BC s zeaxanthin s lutein s lycopene. Organic solvents: zeaxanthin s lutein s lycopene s BC. Two days after supplementation with 5 WM BC in MLCD, cellular BC levels reached a maximum of 140 þ 11 pmol/Wg DNA, leveling off to 100 þ 15 pmol/Wg DNA until day 8. Incubation with BC dissolved in THF/DMSO resulted in a lower BC uptake of 105 þ 14 pmol/Wg DNA and 64 þ 20 pmol/Wg DNA respectively. No cytotoxic effects of these formulations were detected. The results show that the MLCD formulation is an improved method for investigations of carotenoids and other lipophilic compounds in in vitro test systems compared to methods using organic solvents. ß
British Journal of Nutrition, 2007
Carotenoids have been shown to have potential beneficial effects on human health which has led to an increasing interest in the study of their bioavailability. A Caco-2 cell model, as previously described, was employed to examine the percentage transfer of the carotenoids a-carotene, b-carotene, lycopene, astaxanthin, b-cryptoxanthin, lutein and zeaxanthin through an intact, highly differentiated Caco-2 cell monolayer at a range of different amounts. Our results show that astaxanthin, a carotenoid with powerful antioxidant capacity, had the highest percentage transfer overall. We examined the cellular uptake and secretion of lutein and zeaxanthin to compare two structurally similar carotenoids. Both were efficiently transported through the monolayer with a range between 5·1 (SEM 1·2) % to 20·2 (SEM 3·3) % and 5·5 (SEM 2·5) % to 13·4 (SEM 4) % for lutein and zeaxanthin, respectively. These carotenoids were compared to each other at each added amount and no significant difference was observed between the two xanthophylls. The carotene carotenoids a-carotene, b-carotene and lycopene and the xanthophyll b-cryptoxanthin were also examined and had lower uptake and secretion values when compared to lutein, zeaxanthin and astaxanthin. The xanthophyll b-cryptoxanthin was also not significantly different when compared to the carotene carotenoids. Data generated from this study compares well with in vivo bioavailability studies. Furthermore, the model provides comparative data on the relative absorption and transfer of seven different carotenoids. Our data indicate that lower amounts of carotenoids were absorbed and transferred more efficiently than higher amounts suggesting a saturation effect at higher exposure.
Modulation of the carotenoid bioaccessibility through liposomal encapsulation
Colloids and surfaces. B, Biointerfaces, 2014
The low bioaccessibility of carotenoids is currently a challenge to their incorporation in pharmaceutics, nutraceuticals and functional foods. The aim of this study was to evaluate the modulating effects of liposome encapsulation on the bioaccessibility, and its relationship with carotenoid structure and incorporated concentration. The physical stability of liposomes, lipid digestibility, carotenoids release and bioaccessibility were investigated during incubation in a simulated gastrointestinal tract. Analysis on the liposome size and morphology showed that after digestion, the majority of particles maintained spherical shape with only an increase of size in liposomes loading β-carotene or lutein. However, a large proportion of heterogeneous particles were visible in the micelle phase of liposomes loading lycopene or canthaxanthin. It was also found that the release of lutein and β-carotene from liposomes was inhibited in a simulated gastric fluid, while was slow and sustained in a...
Mammalian carotenoid absorption and metabolism
Pure and Applied Chemistry, 2000
Carotenoids are purported to provide widespread function in the biology and health of humans and other mammalian species. Provitamin A carotenoids, such as b-carotene, are valued in the diet of many mammals for their contribution as precursors of vitamin A and retinoids. Carotenoids may also function in the prevention of some chronic diseases by improving intercellular communication. enhancing immune response, and operating as antioxidants in vivo. It is widely known that humans and other mammalian species absorb and accumulate carotenoids in body tissues. However, the potential use of carotenoids as modulators of disease and in the prevention of vitamin A de®ciency has been hindered by the limited progress in understanding carotenoid absorption and metabolism. In fact, major gaps in knowledge still exist in the fundamental pathways beginning with release from the food matrix and ending with distribution in body tissues and excretion. Continued development of assessment methods for humans, appropriate animal models for mechanistic studies, and analytical techniques for quanti®cation and identi®cation of compounds is needed to advance our understanding of these critical pathways. This review will discuss the current knowledge involving the fundamental pathways of absorption and metabolism of carotenoids in mammalian species. When applicable, emphasis will be placed on the human. junctional communication . Of the provitamin A carotenoids, only b-carotene has been shown to induce the gap junction protein, connexin . Other non-provitamin A carotenoids, such as canthaxanthin, also contain the six-membered ring structure and are quite active in the induction of connexin . Lycopene is an exception because it has the ability to induce connexin, but lacks the ring structure. The structure of lycopene, a straight chain polyene, may have additional biological activity related to its antioxidant properties .
The Journal of Nutrition
The mechanisms responsible for the movement of absorbed carotenoids between intracellular organdÃ-es and for the incorporation of carotenoids into serum lipoproteins are unknown. It was the objec tive of this study to use bovine liver and intestine as a model to study the possible cytosolic protein-mediated carotenoid transfer between liposomes and mitochon dria in vitro. Liposomes containing /3-[3H]carotene were incubated with isolated bovine hepatic mitochondria (1 mg protein) and various quantities of liver cytosol or intestinal mucosa! cell cytosol (0-6 mg protein) for up to l h at 37°C. The /3-[3H]carotene activity in liposomes was then measured over time to determine percent transfer of j3-carotene to mitochondria. Over the time period studied, the rate of /3-carotene transfer was un affected by increasing levels of either hepatic or intesti nal cytosolic protein. These results suggest that unlike many other lipid species, ¡ntracellulartransport of ßcarotene is not mediated by cytosolic transport pro teins and must occur by other mechanisms such as vesicular transport or by membrane-bound pro teins.
In vitro screening of relative bioaccessibility of carotenoid from foods
Asia Pacific Journal of Clinical Nutrition
Carotenoids are lipophilic pigments in plant foods that are of particular interest as precursors of vitamin A, a nutrient required for vision, cell differentiation, and the immune system. In order to mediate such activities, carotenoids and their metabolites must be absorbed for delivery to tissues. Unlike many other dietary lipids, the efficiency of carotenoid absorption is typically inefficient, being affected by food matrix, style of processing, other dietary components, and nutritional and physiological status. Thus, reliable prediction of carotenoid bioavailability is problematic. We have developed a relatively simple and cost effective procedure to study the potential bioavailability, i.e., the bioaccessibility, of carotenoids. The method involves simulated oral, gastric and small intestinal digestion of test samples to access the efficiency of incorporation into micelles, an obligatory step for absorption of lipophilic compounds. The model can be further expanded by adding micelles generated during small intestinal phase of digestion to monolayers of Caco-2 human intestinal epithelial cells to investigate apical uptake, cellular metabolism and transepithelial transport of carotenoids. Recent work by Borel and associates has demonstrated that the relative bioaccessibility of carotenoids observed in vitro is highly correlated with in vivo observations and results from bioavailability trials with human subjects. Results from recent studies using the in vitro model to screen relative bioaccessibility of β-carotene in various cultivars of cassava, impact of amount and types of fatty acyl groups in triglycerides on micellarization of carotenoids, and the mechanism of digestion and intestinal cell uptake of xanthophyll esters are presented.
In vitro screening of relative bioaccessibility of carotenoids from foods
Asia Pacific journal of clinical nutrition, 2008
Carotenoids are lipophilic pigments in plant foods that are of particular interest as precursors of vitamin A, a nutrient required for vision, cell differentiation, and the immune system. In order to mediate such activities, carotenoids and their metabolites must be absorbed for delivery to tissues. Unlike many other dietary lipids, the efficiency of carotenoid absorption is typically inefficient, being affected by food matrix, style of processing, other dietary components, and nutritional and physiological status. Thus, reliable prediction of carotenoid bioavailability is problematic. We have developed a relatively simple and cost effective procedure to study the potential bioavailability, i.e., the bioaccessibility, of carotenoids. The method involves simulated oral, gastric and small intestinal digestion of test samples to access the efficiency of incorporation into micelles, an obligatory step for absorption of lipophilic compounds. The model can be further expanded by adding mi...
Incorporation of carotenoid esters into liposomes
Biophysical Chemistry, 2005
Carotenoid esters are investigated for their interaction with liposomal membranes and compared with their corresponding free (non-esterified) carotenoids. A monoester (β-cryptoxanthin) and two diesters (zeaxanthin and lutein) were chosen. Egg yolk phosphatidylcholine liposomes served as the membrane model. We measured the sizes of the liposomes by photon correlation spectroscopy. The incorporation yields were determined spectrophotometrically. From liposomes simultaneously doped with the fluorescent dye Laurdan, fluidity changes of the liposomes were obtained.In summary, the results indicate that the carotenoid esters: (i) get incorporated, but at a lower yield than their corresponding free carotenoids, (ii) also increase the membrane rigidity as do the free carotenoids, and (iii) increase the liposome sizes significantly, but after extrusion through an 0.1 μm filter the sizes resemble with the exception of the liposomes incorporated with lutein diesters, they remain bigger indicating an elastic property due to two different accessible locations in the membrane.
The Journal of Nutritional Biochemistry, 1999
Despite the interest in the diverse roles of dietary carotenoids in human health, little is known about the transfer of these plant pigments from foods to micelles during digestion and their subsequent transfer across the intestinal epithelium. We conducted this study to characterize the intestinal uptake of micellarized carotenoids using monolayers of differentiated Caco-2 human intestinal cells. Crystalline β-carotene (BC) and lutein (LUT), solubilized in mixed micelles for delivery to cells, were stable in a tissue culture environment for 20 hours. Cellular accumulation of micellar BC and LUT was proportional to the media content of carotenoids at ≤2 μmol/L and the length of exposure. Cellular accumulation of BC routinely exceeded LUT and was due in part to the enhanced efflux or possible metabolism of LUT. Cellular BC content increased in a curvilinear manner when cultures were incubated in micellar medium containing 2 to 27 μmol/L BC prepared from water miscible beadlets; cellular BC content was maximum when medium BC was ≥18 μmol/L. There was no indication that high levels of BC in medium or within cells adversely affected micellar LUT accumulation. These data support the use of the Caco-2 human cell line as a model for studying the intestinal uptake, absorption, and possible interactions of dietary carotenoids.