Bioaccessibility of carotenoids and vitamin E from their main dietary sources

Vitamin E and carotenoids are fat-soluble microconstituents that may exert beneficial effects in humans, including protection against cancer, cardiovascular diseases, and age-related eye diseases. Their bioavailability is influenced by various factors including food matrix, formulation, and food processing. Since human studies are labor-intensive, time-consuming, and expensive, the in vitro model used in this study is increasingly being used to estimate bioaccessibility of these microconstituents. However, the ability of this model to predict bioavailability in a healthy human population has not yet been verified. The first aim of this study was to validate this model by comparing model-derived bioaccessibility data with (i) human-derived bioaccessibility data and (ii) published mean bioavailability data reported in studies involving healthy humans. The second aim was to use it to measure alpha- and gamma-tocopherol, beta-carotene, lycopene, and lutein bioaccessibility from their main dietary sources. Bioaccessibility as assessed with the in vitro model was well correlated with human-derived bioaccessibility values (r = 0.90, p < 0.05), as well as relative mean bioavailability values reported in healthy human groups (r = 0.98, p < 0.001). The bioaccessibility of carotenoids and vitamin E from the main dietary sources was highly variable, ranging from less than 0.1% (beta-carotene from raw tomato) to almost 100% (alpha-tocopherol from white bread). Bioaccessibility was dependent on (i) microconstituent species (lutein > beta-carotene and alpha-carotene > lycopene and alpha-tocopherol generally > gamma-tocopherol), (ii) food matrix, and (iii) food processing.     

Impact of fatty acyl composition and quantity of triglycerides on bioaccessibility of dietary carotenoids

A carotenoid-rich salad meal with varying amounts and types of triglycerides (TG) was digested using simulated gastric and small intestinal conditions. Xanthophylls (lutein and zeaxanthin) and carotenes (alpha-carotene, beta-carotene, and lycopene) in chyme and micelle fraction were quantified to determine digestive stability and efficiency of micellarization (bioaccessibility). Micellarization of lutein (+zeaxanthin) exceeded that of alpha- and beta-carotenes, which was greater than that of lycopene for all test conditions. Micellarization of carotenes, but not lutein (+zeaxanthin), was enhanced (P < 0.05) by addition of TG (2.5% v/w) to the meal and was dependent on fatty acyl chain length in structured TG (c18:1 > c8:0 > c4:0). The degree of unsaturation of c18 fatty acyl chains in TG added to the salad purée did not significantly alter the efficiency of micellarization of carotenoids. Relatively low amounts of triolein and canola oil (0.5-1%) were required for maximum micellarization of carotenes, but more oil (approximately 2.5%) was required when TG with medium chain saturated fatty acyl groups (e.g., trioctanoin and coconut oil) was added to the salad. Uptake of lutein and beta-carotene by Caco-2 cells also was examined by exposing cells to micelles generated during the simulated digestion of salad purée with either triolein or trioctanoin. Cell accumulation of beta-carotene was independent of fatty acyl composition of micelles, whereas lutein uptake was slightly, but significantly, increased from samples with digested triolein compared to trioctanoin. The results show that the in vitro transfer of alpha-carotene, beta-carotene, and lycopene from chyme to mixed micelles during digestion requires minimal (0.5-1%) lipid content in the meal and is affected by the length of fatty acyl chains but not the degree of unsaturation in TG. In contrast, fatty acyl chain length has limited if any impact on carotenoid uptake by small intestinal epithelial cells. These data suggest that the amount of TG in a typical meal does not limit the bioaccessibility of carotenoids.     

Evaluation of brief dietary questions to estimate vegetable and fruit consumption - using serum carotenoids and red-cell folate

OBJECTIVE: To evaluate responses to self-administered brief questions regarding consumption of vegetables and fruit by comparison with blood levels of serum carotenoids and red-cell folate. DESIGN: A cross-sectional study in which participants reported their usual intake of fruit and vegetables in servings per day, and serum levels of five carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin and lycopene) and red-cell folate were measured. Serum carotenoid levels were determined by high-performance liquid chromatography, and red-cell folate by an automated immunoassay system. SETTINGS AND SUBJECTS: Between October and December 2000, a sample of 1598 adults aged 25 years and over, from six randomly selected urban centres in Queensland, Australia, were examined as part of a national study conducted to determine the prevalence of diabetes and associated cardiovascular risk factors. RESULTS: Statistically significant (P<0.01) associations with vegetable and fruit intake (categorised into groups: /=4 servings per day) were observed for alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin and red-cell folate. The mean level of these carotenoids and of red-cell folate increased with increasing frequency of reported servings of vegetables and fruit, both before and after adjusting for potential confounding factors. A significant association with lycopene was observed only for vegetable intake before adjusting for confounders. CONCLUSIONS: These data indicate that brief questions may be a simple and valuable tool for monitoring vegetable and fruit intake in this population.     

Relationship of carotenoids and tocopherols in a sample of carrot root-color accessions and carrot germplasm carrying Rp and rp alleles

Carotenoids and tocopherols are powerful antioxidants synthesized in plants from a common precursor. They may offer significant health benefits to humans. Seed oils have been shown to possess high levels of tocopherols, but little is known about their levels in the edible portions of most vegetable crops. A two-year field experiment was conducted at two locations to assess levels of major carotenoids and tocopherols in carrot (Daucus carota) root and leaf tissue. Levels of compounds in root tissue reported on a dry weight basis were as follows: alpha-tocopherol, 0.04-0.18 ppm; lycopene, 0.00-52.94 ppm; alpha-carotene, 10.63-1504.76 ppm; and beta-carotene, 26.69-1673.76 ppm. Higher levels of all carotenoids were measured in phloem tissue than in xylem. Leaf tissue levels of tocopherols measured on a dry weight basis ranged from 0.02 to 0.85 ppm, whereas levels of carotenoids ranged from 12.81 to 411.66 ppm. In xylem tissue, alpha-tocopherol was significantly (P < or =0.001) positively correlated with alpha-carotene (r = 0.65) and with beta-carotene (r = 0.52). This positive correlation indicates it may be possible to select for both increased alpha-tocopherol and carotenoids in carrot. The reduced pigment (rp) mutation of carrot exhibited a 96% reduction in levels of alpha- and beta-carotene and a 25-43% reduction in alpha-tocopherol when compared to a near-isogenic line. In plants homozygous for rp, a substantial increase was observed in phytoene, a precursor to carotenoids, suggesting the location of the rp lesion in the carotenoid synthesis pathway.     

Rapid electrochemical method for the evaluation of the antioxidant power of some lipophilic food extracts.

In this paper, a novel electrochemical method to evaluate the antioxidant power of lipophilic compounds present in vegetables, such as carotenoids, chlorophylls, tocopherols, and capsaicin, is reported. The method is based on a flow injection system with an electrochemical detector equipped with a glassy carbon working electrode operating amperometrically at a potential of + 0.5 V (vs Ag/AgCl). The proposed method is selective for lipophilic compounds having antioxidant power. When applied to pure compounds, the order of antioxidant power resulted as follows: lycopene > beta-carotene > zeaxanthin > alpha-carotene > beta-cryptoxanthin > lutein > alpha-tocopherol > capsaicin > chlorophyll a > chlorophyll b > astaxanthin > canthaxanthin. Results obtained on five vegetable and two fruit extracts were compared to those obtained by the 2,2'-azinobis(3-ethylbenz-thiazoline-6-sulfonic) acid (ABTS) radical cation decolorization assay, one of the most used methods to evaluate the total antioxidant capacity of foods. A good correlation between the two methods was found, except for spinach, because of the different antioxidant powers assigned by the two methods to chlorophylls. In conclusion, results suggest that the proposed electrochemical method can be successfully employed for the direct, rapid, and reliable monitoring of the antioxidant power of lipophilic food extracts.     

Change in carotenoids and antioxidant vitamins in tomato as a function of varietal and technological factors

The change in the carotenoid and bioantioxidant content of tomato as a function of varietal and technological factors was investigated in the present work. No great differences were found between cultivars for fresh consumption (salad tomatoes) and those for processing in ascorbic acid content. The concentration of ascorbic acid ranged between 14.6 and 21.7 mg/100 g fresh weight of ripe tomato fruit. Processing cultivars contained higher amounts of tocopherols, particularly alpha-tocopherol than tomatoes for fresh consumption. Significant differences could be obtained between the examined varieties with regard to carotenoid concentration. The different tomatoes varied not only in the total carotenoid content but also in the qualitative distribution of some pigments such as lycopene, beta-carotene and lutein. During heat-based processing, ascorbic acid, tocopherols, and carotenoids showed different role and response. Ascorbic acid, alpha-tocopherol quinone, and beta-carotene were the most susceptible components toward thermal degradation.     

Association of carotenoids, tocopherols and vitamin C in plasma with allergic rhinitis and allergic sensitisation in adults

OBJECTIVES: Antioxidant nutrients like carotenoids, tocopherols and vitamin C have been suggested to protect against allergic rhinitis and allergic sensitisation but scientific evidence is scarce. The aims of the study were to measure the plasma concentration of six carotenoids, alpha- and gamma-tocopherol and vitamin C as biomarkers of the intake, absorption and subsequent metabolism of these nutrients, and to assess their association with allergic rhinitis and sensitisation. METHOD: Data from a cross-sectional study on representative dietary and lifestyle habits of the population of Bavaria, Germany, were analysed. The plasma levels of six carotenoids (alpha-carotene, beta-carotene, lycopene, lutein/zeaxanthin, canthaxanthin and cryptoxanthin) as well as of alpha-tocopherol, gamma-tocopherol and vitamin C were measured in 547 adults aged between 19 and 81 years. Participants with specific serum immunoglobulin E > or =700 U l(-1) were categorised as sensitised. The association of plasma antioxidant levels, allergic rhinitis and allergic sensitisation was assessed by means of unconditional logistic regression models. RESULTS: We observed a negative association between plasma total carotenoids and the prevalence of allergic rhinitis, with odds ratio (95% confidence interval) of 1.13 (0.54-2.39) for the second, 0.72 (0.33-1.58) for the third and 0.44 (0.19-1.03) for the fourth quartile of total carotenoids concentration (P for trend=0.0332); results for lycopene failed to reach statistical significance (P=0.0608). Other single carotenoids, tocopherols and vitamin C were unrelated to allergic rhinitis. Allergic sensitisation was negatively associated with plasma gamma-tocopherol, with odds ratio (95% confidence interval) of 0.92 (0.51-1.65) for the second, 1.00 (0.56-1.80) for the third and 0.45 (0.23-0.88) for the fourth quartile of plasma gamma-tocopherol concentration (P for trend=0.0410). No other antioxidant was significantly related to allergic sensitisation. CONCLUSIONS: High plasma carotenoid concentrations reflecting a diet high in various fruits and vegetables might have a protective effect on allergic rhinitis in adulthood.     

Bioaccessibility of beta-carotene, lutein, and lycopene from fruits and vegetables

Epidemiological studies have consistently demonstrated that there is an association between carotenoid-rich food intakes with a low incidence in chronic diseases. Nevertheless, there is not an association between the intake of total dietary carotenoids and chronic health incidence in the European population, probably because of different carotenoid food sources and bioavailability. The objective of this study was to evaluate the small and large intestine bioaccessibilities of major dietary carotenoids from fruits and vegetables in a common diet. A bioaccessibility model that includes enzymatic digestion and in vitro colonic fermentation was employed. Lutein presented greater small intestine bioaccessibility (79%) than beta-carotene (27%) or lycopene (40%). With regard to large intestine bioaccessibility, similar amounts of lycopene and beta-carotene were released from the food matrix (57%), whereas small amounts of lutein (17%) were released. These results suggest that 91% of the beta-carotene, lutein, and lycopene contained in fruits and vegetables is available in the gut during the entire digestion process. Colonic fermentation is shown to be important for carotenoid availability in the gut.     

Comparison of the bioavailability of natural palm oil carotenoids and synthetic beta-carotene in humans

Palm oil carotenoids are a mixture of alpha- and beta-carotenes, which are used as food colorants. They may also be applied as a functional food ingredient because of the provitamin A activity of alpha- and beta-carotenes and their proposed beneficial roles in the prevention of chronic diseases. This paper discusses the results of an incomplete balanced crossover study with 69 healthy adult volunteers to compare palm oil carotenoids with synthetic beta-carotene in their efficacies to increase plasma levels of carotenoids. Four days of supplementation with natural palm oil carotenoids (7.6 mg/day of alpha-carotene, 11.9 mg/day of all-trans-beta-carotene, 7.5 mg/day of cis-beta-carotene) or synthetic beta-carotene (23.8 mg/day of all-trans-beta-carotene, 4.4 mg/day of cis-beta-carotene), added to a mixed meal, resulted in significant increases in plasma levels of the supplied carotenoids as compared to consumption of a low-carotenoid meal (i.e., 7.2-fold increase in alpha-carotene and 3.5-fold increase in all-trans-beta-carotene following palm oil carotenoids; 6.9-fold increase in all-trans beta-carotene following synthetic beta-carotene). As the carotenoid content differed between the treatments, the relative plasma responses were calculated per milligram of beta-carotene intake. These were similar for the two supplements, suggesting that the presence of alpha-carotene does not affect the bioavailability of beta-carotene from palm oil. It was concluded that 4 days of supplementation with palm oil carotenoids or synthetic beta-carotene improves the plasma beta-carotene status substantially, whereas alpha-carotene is additionally delivered by the palm oil supplement.     

Carotenoids in white- and red-fleshed loquat fruits

Fruits of 23 loquat ( Eriobotrya japonica Lindl.) cultivars, of which 11 were white-fleshed and 12 red-fleshed, were analyzed for color, carotenoid content, and vitamin A values. Color differences between two loquat groups were observed in the peel as well as in the flesh. beta-Carotene and lutein were the major carotenoids in the peel, which accounted for about 60% of the total colored carotenoids in both red- and white-fleshed cultivars. beta-Cryptoxanthin and, in some red-fleshed cultivars, beta-carotene were the most abundant carotenoids in the flesh, and in total, they accounted for over half of the colored carotenoids. Neoxanthin, violaxanthin, luteoxanthin, 9- cis-violaxanthin, phytoene, phytofluene, and zeta-carotene were also identified, while zeaxanthin, alpha-carotene, and lycopene were undetectable. Xanthophylls were highly esterified. On average, 1.3- and 10.8-fold higher levels of colored carotenoids were observed in the peel and flesh tissue of red-fleshed cultivars, respectively. The percentage of beta-carotene among colored carotenoids was higher in both the peel and the flesh of red-fleshed cultivars. Correlations between the levels of total colored carotenoids and the color indices were analyzed. The a* and the ratio of a*/ b* were positively correlated with the total content of colored carotenoids, while L*, b*, and H degrees correlated negatively. Vitamin A values, as retinol equivalents (RE), of loquat flesh were 0.49 and 8.77 microg/g DW (8.46 and 136.41 microg/100 g FW) on average for white- and red-fleshed cultivars, respectively. The RE values for the red-fleshed fruits were higher than fruits such as mango, red watermelon, papaya, and orange as reported in the literature, suggesting that loquat is an excellent source of provitamin A.     

Evaluation of analytical methods for carotenoid extraction from biofortified maize (Zea mays sp.)

Biofortification of maize with beta-carotene has the potential to improve vitamin A status in vitamin A deficient populations where maize is a staple crop. Accurate assessment of provitamin A carotenoids in maize must be performed to direct breeding efforts. The objective was to evaluate carotenoid extraction methods and determine essential steps for use in countries growing biofortified maize. The most reproducible method based on coefficient of variation and extraction efficiency was a modification of Kurilich and Juvik (1999). Heat and saponification are required to release carotenoids from biofortified maize and remove oils interfering with chromatographic analysis. For maize samples with high oil content, additional base may be added to ensure complete saponification without compromising results. Degradation of internal standard before carotenoids were released from the maize matrix required the addition of internal standard after heating to prevent overestimation of carotenoids. This modified method works well for lutein, zeaxanthin, beta-cryptoxanthin, alpha-carotene, and beta-carotene.     

Mechanism of deactivation of triplet-excited riboflavin by ascorbate, carotenoids, and tocopherols in homogeneous and heterogeneous aqueous food model systems

Tocopherols (alpha, beta, gamma, and delta) and Trolox were found to deactivate triplet-excited riboflavin in homogeneous aqueous solution (7:3 v/v tert-butanol/water) with second-order reaction rates close to diffusion control [k2 between 4.8 x 10(8) (delta-tocopherol) and 6.2 x 10(8) L mol(-1) s(-1) (Trolox) at 24.0 +/- 0.2 degrees C] as determined by laser flash photolysis transient absorption spectroscopy. In aqueous buffer (pH 6.4) the rate constant for Trolox was 2.6 x 10(9) L mol(-1) s1 and comparable to the rate constant found for ascorbate (2.0 x 10(9) L mol(-1) s(-1)). The deactivation rate constant was found to be inferior in heterogeneous systems as shown for alpha-tocopherol and Trolox in aqueous Tween-20 emulsion (approximately by a factor of 4 compared to 7:3 v/v tert-butanol/water). Neither beta-carotene (7:3 v/v tert-butanol/water and Tween-20 emulsion), lycopene (7:3 v/v tert-butanol/water), nor crocin (aqueous buffer at pH 6.4, 7:3 v/v tert-butanol/water, and Tween-20 emulsion) showed any quenching on the triplet excited state of riboflavin. Therefore, all carotenoids seem to reduce the formation of triplet-excited riboflavin through an inner-filter effect. Activation parameters were based on the temperature dependence of the triplet-excited deactivation between 15 and 35 degrees C, and the isokinetic behavior, which was found to include purine derivatives previously studied, confirms a common deactivation mechanism with a bimolecular diffusion-controlled encounter with electron (or hydrogen atom) transfer as rate-determining step. DeltaH for deactivation by ascorbic acid, Trolox, and homologue tocopherols (ranging from 18 kJ mol(-1) for Trolox in Tween-20 emulsion to 184 kJ mol(-1) for ascorbic acid in aqueous buffer at pH 6.4) showed a linear dependence on DeltaS (ranging from -19 J mol(-1) K(-1) for Trolox in aqueous buffer at pH 6.4 to +550 J mol(-1) K(-1) for ascorbic acid in aqueous buffer pH 6.4). Among photooxidation products from the chemical quenching, lumicrome, alpha-tocopherol quinones and epoxyquinones, and alpha-tocopherol dimers were identified by ESI-QqTOF-MS.     

Supercritical fluid extraction of lycopene from tomato processing byproducts

Tomato seeds and skins acquired from the byproduct of a local tomato processing facility were studied for supercritical fluid extraction (SFE) of phytochemicals. The extracts were analyzed for lycopene, beta-carotene, alpha-carotene, alpha-tocopherol, gamma-tocopherol, and delta-tocopherol content using high-performance liquid chromatography-electrochemical detection and compared to a chemically extracted control. SFEs were carried out using CO(2) at seven temperatures (32-86 degrees C) and six pressures (13.78-48.26 MPa). The effect of CO(2) flow rate and volume also was investigated. The results indicated that the percentage of lycopene extracted increased with elevated temperature and pressure until a maximum recovery of 38.8% was reached at 86 degrees C and 34.47 MPa, after which the amount of lycopene extracted decreased. Conditions for the optimum extraction of lycopene from 3 g of raw material were determined to be 86 degrees C, 34.47 MPa, and 500 mL of CO(2) at a flow rate of 2.5 mL/min. These conditions resulted in the extraction of 61.0% of the lycopene (7.19 microg lycopene/g).     

Use of fluorogenic probes to differentiate between hydrophilic and lipophilic antioxidant activity in a fish cell line

In finfish aquaculture, dietary antioxidants have been shown to improve indicators of general fish health and to inhibit the oxidative deterioration of polyunsaturated fatty acids. To facilitate the characterization of novel antioxidants or antioxidant mixtures, we developed assays for antioxidant activity in a fish cell line. We used 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFDA) to determine the protective effects of a panel of representative antioxidant compounds against the formation of reactive oxygen species (ROS) under conditions that promote oxidative stress, whereas protective effects against lipid peroxidation were measured using the thiobarbituric acid reactive substances (TBARS) assay and a novel implementation of 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C(11)-BODIPY(581/591)). We found that the highly hydrophilic antioxidant, sodium ascorbate, inhibited H(2)DCFDA oxidation but had no effect on lipid peroxidation, whereas the highly hydrophobic antioxidant, α-tocopherol, potently inhibited lipid peroxidation but did not prevent H(2)DCFDA oxidation. The data suggest that a single assay is not sufficient for estimating antioxidant activity in cultured fish cells.     

Fatty acid and carotenoid composition of gac (Momordica cochinchinensis Spreng) fruit

In this study, we analyzed fatty acid and carotenoid composition of fruit tissues, including seed (which are surrounded by a bright red, oily aril) of Momordica cochinchinensis Spreng, known as gac in Vietnam. Carotenoid content was analyzed by reversed-phase HPLC, using a C(30) column and a method separating cis- and trans-isomers of the major carotenoids in this fruit. Mean values obtained in aril tissues were 1342 microg trans-, 204 microg cis-, and 2227 microg total lycopene; 597 microg trans-, 39 microg cis-, and 718 microg total beta-carotene; and 107 microg alpha-carotene/g FW. Mesocarp contained 11 microg trans-, 5 microg cis-beta-carotene/g FW, trace amounts of alpha-carotene, and no lycopene. Gac aril contained 22% fatty acids by weight, composed of 32% oleic, 29% palmitic, and 28% linoleic acids. Seeds contained primarily stearic acid (60.5%), smaller amounts of linoleic (20%), oleic (9%), and palmitic (5-6%) acids, and trace amounts of arachidic, cis-vaccenic, linolenic, and palmitoleic, eicosa-11-enoic acids, and eicosa-13-enoic (in one fruit only) acids.     

Hydrolysis kinetics of astaxanthin esters and stability of astaxanthin of Haematococcus pluvialis during saponification

The reaction kinetics for the hydrolysis of astaxanthin esters and the degradation of astaxanthin during saponification of the pigment extract from the microalga Haematococcus pluvialis were investigated. Different concentrations of sodium hydroxide in methanol were used for the saponification under nitrogen in darkness at ambient temperature (22 degrees C) followed by the analysis of astaxanthins and other carotenoids using an HPLC method. The concentration of methanolic NaOH solution was important for promoting the hydrolysis of astaxanthin esters and minimizing the degradation of astaxanthin during saponification. With a higher concentration of methanolic NaOH solution, the reaction rate of hydrolysis was high, but the degradation of astaxanthin occurred significantly. The rate constants of the hydrolysis reaction (first order) of astaxanthin esters and the degradation reaction (zero-order) of astaxanthin were directly proportional to the concentration of sodium hydroxide in the saponified solution. Although the concentration of sodium hydroxide in the saponified solution was 0.018 M, complete hydrolysis of astaxanthin esters was achieved in 6 h for different concentrations (10-100 mg/L) of pigment extracts. Results also indicated that a higher temperature should be avoided to minimize the degradation of astaxanthin. In addition, during saponification, no loss of lutein, beta-carotene, and canthaxanthin was found.     

Assessment of selected antioxidants in tomato pomace subsequent to treatment with the edible oyster mushroom, Pleurotus ostreatus, under solid-state fermentation

Tomato pomace, delignified by the edible oyster mushroom, Pleurotus ostreatus, could be used as a poultry feed ingredient to provide alpha-tocopherol for retardation of lipid oxidation in postmortem meat if the antioxidant were retained in pomace after fungal fermentation. Experiments were conducted to investigate changes in the content of alpha-tocopherol, lycopene, and beta-carotene in tomato pomace after sterilization and treatment with P. ostreatus from 0 to 104 days. alpha-Tocopherol (39.26 to 31.15 microg/g) and lycopene (17.42 to 11.19 microg/g) significantly decreased during sterilization while beta-carotene (42.56 to 35.44 microg/g) did not. The content of carotenoids decreased by day 26 as compared to 0 day for the control and for treated samples. alpha-Tocopherol decreased during fungal fermentation at day 26 as compared to 0 day for the control and increased during the same period for treated samples. By 104 days, only alpha-tocopherol in control pomace was present in a significant amount. The alpha-tocopherol content of mushroom fruit grown in pomace (74.10 microg/g) and in wheat straw (51.36 microg/g) was not significantly different. Tomato pomace could be used as a substrate to successfully grow edible mushrooms; however, the initial level of selected antioxidants and their reduction during fungal fermentation must be considered when delignified pomace is utilized for selected nutrient content in animal feed or products for human consumption.     

Determination of major carotenoids in a few Indian leafy vegetables by high-performance liquid chromatography

Leafy vegetables [Basella rubra L., Peucedanum sowa Roxb., Moringa oleifera Lam., Trigonella foenum-graecum L., Spinacia oleracea L., Sesbania grandiflora (L.) Poir., and Raphanus sativus L.] that are commonly used by the rural population in India were evaluated in terms of their main carotenoid pattern. The extracted carotenoids were purified by open column chromatography (OCC) on a neutral alumina column to verify their identity by their characteristic UV-visible absorption spectra. Reverse-phase high-performance liquid chromatography (HPLC) on a C18 column with UV-visible photodiode array detection under isocratic conditions was used for quantification of isolated carotenoids. Acetonitrile/methanol/dichloromethane (60:20:20 v/v/v) containing 0.1% ammonium acetate was used as a mobile phase. The major carotenoids identified by both methods were lutein, beta-carotene, violaxanthin, neoxanthin, and zeaxanthin. Among the carotenoids identified, lutein and beta-carotene levels were found to be higher in these leafy vegetables. Results show that P. sowa and S. oleracea are rich sources of lutein (77-92 mg/100 g of dry wt) and beta-carotene (36-44 mg/100 g of dry wt) compared with other leafy vegetables. The purity of carotenoids eluted by OCC was clarified by HPLC, and they were found to be 92% +/- 3% for neoxanthin, 94% +/- 2% for violaxanthin, 97% +/-2% for lutein and zeaxanthin, and 90% +/- 3% for beta-carotene. It could be recommended to use P. sowa and S. oleracea as rich sources of lutein and beta-carotene for health benefits. The OCC method proposed is relatively simple and provides purified carotenoids for feeding trials.     

Effects of ozone and oxygen on the degradation of carotenoids in an aqueous model system

The effects of ozone and oxygen on the degradation of carotenoids in an aqueous model system were studied. All-trans beta-carotene, 9-cis beta-carotene, beta-cryptoxanthin, and lycopene were adsorbed onto a C(18) solid phase and exposed to a continuous flow of water saturated with oxygen or ozone at 30 degrees C. Carotenoids were analyzed using HPLC with a C(30) column and a photodiode array detector. Approximately 90% of all-trans beta-carotene, 9-cis beta-carotene, and beta-cryptoxanthin were lost after exposure to ozone for 7 h. A similar loss of lycopene occurred in only 1 h. When exposed to oxygen, all carotenoids, except beta-cryptoxanthin, degraded at lower rates. The degradation of all the carotenoids followed zero-order reaction kinetics with the following relative rates: lycopene > beta-cryptoxanthin > all-trans beta-carotene > 9-cis beta-carotene. The major degradation products of beta-carotene were tentatively identified on the basis of their elution on the HPLC column, UV-Vis spectra, and electrospray LC-MS. Predominant isomers of beta-carotene were 13-cis, 9-cis, and a di-cis isomer. Products resulting from cleavage of the molecule were beta-apo-13-carotenone and beta-apo-14'-carotenal, whereas epoxidation yielded beta-carotene 5,8-epoxide and beta-carotene 5, 8-endoperoxide.     

Development of an in vitro digestion method to assess carotenoid bioavailability from meals.

The objective of this study was to develop a model for assessing the bioavailability of carotenoids from meals using an in vitro digestion procedure. A meal was prepared using baby food carrots, spinach, and a meat, plus tomato paste. The aqueous fraction was isolated from digesta to determine the quantity of carotenoids transferred from the food to micelles. The micellarization of lutein (25-40%) exceeded (p < 0.01) that of alpha- and beta-carotene (12-18%) and lycopene (<0.5%). Micellarization of carotenoids was not affected by elimination of the gastric phase of the digestive process. The absence of bile extract prevented the transfer of carotenoids from foods to micelles, whereas omission of pancreatin only reduced the micellarization of the carotenes. Differentiated cultures of Caco-2 human intestinal cells accumulated 28-46% of micellarized carotenoids from the medium after 6 h. These results support the usefulness of the in vitro digestion process as a rapid and cost-effective model for screening the bioavailability of carotenoids from meals.