beta-carotene and apocarotenal

β-Carotene is the major dietary source of provitamin A. Central cleavage of β-carotene yields 2 molecules of retinal followed by further oxidation to retinoic acid. Eccentric cleavage of β-carotene occurs at double bonds other than the central double bond, and the products of these reactions are β-apocarotenals and β-apocarotenones. We reviewed recent developments in 3 areas: 1): the enzymatic production of β-apocarotenoids in higher animals; 2) the occurrence of β-apocarotenoids in foods and animal tissues; and 3) the biological activity of β-apocarotenoids, particularly on retinoid receptors. HPLC-mass spectrometry techniques were developed to quantify these compounds in mouse serum and tissues and in foods. β-Apo-10'- and -12'-carotenals were detected in mouse serum and liver. β-Apo-8'-, β-apo-10'-, β-apo-12'-, and β-apo-14'-carotenals and β-apo-13-carotenone were detected in orange-fleshed melons. Transactivation assays were performed to see whether apocarotenoids activate or antagonize retinoid X receptor (RXR) α. Reporter gene constructs and retinoid receptor (RXRα) were transfected into cells, which were used to perform quantitative assays for the activation of this ligand-dependent transcription factor. None of the β-apocarotenoids significantly activated RXRα. However, β-apo-13-carotenone antagonized the 9-cis-retinoic acid activation of RXRα. Competitive radioligand binding assays showed that this antagonist competes directly with the agonist for binding to purified receptor, a finding confirmed by molecular modeling studies. These findings suggest that a possible biological function of β-apocarotenoids is their ability to interfere with nuclear receptor signaling. Recent work showed that β-apo-13-carotenone is also a high-affinity antagonist of all 3 retinoic acid receptors (RARα, RARβ, and RARγ).

Topics: Animals; beta Carotene; Carotenoids; Food; Mice; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Signal Transduction; Transcriptional Activation; Tretinoin

Topics: Absorption; Animals; beta Carotene; Carotenoids; Chemical Phenomena; Chemistry; Drug Stability; Food Analysis; Humans; Stereoisomerism; Vitamin A; Vitamin A Deficiency

The carotenoids are a chemically related group of pigments which occur widely and abundantly in nature. Fruits, vegetables and vegetable oils, dairy products, leaves, shrimp, lobster, the plumage of exotic birds, all contain carotenoids. Chemically, the carotenoids may be divided into carotenes, made up of carbon and hydrogen only, and oxycarotenoids containing oxygen in addition to carbon and hydrogen. The use of carotenoid-containing plant extracts for coloring foods has been practiced for centuries and continues today. Advances in chemical synthesis resulted in the complete laboratory synthesis of beta carotene in 1950. Since then the commercial synthesis of several carotenoids has been accomplished. In the U.S. three of these commercially synthesized carotenoids, beta-carotene, beta-apo-8'-carotenal, and canthaxanthin, are accepted color additives for use in foods and are exempt from certification. These three carotenoids are also widely accepted for food use in other countries. This paper deals with the chemistry and synthesis of these three carotenoids, with special emphasis on their numerous commercially available market forms and their characteristics, and on the application of these carotenoids in the coloring of food products.

Topics: beta Carotene; Beverages; Canthaxanthin; Carotenoids; Chemical Phenomena; Chemistry; Dairy Products; Dietary Fats; Drug Stability; Eggs; Food Coloring Agents; Food Handling; Food, Formulated; Fruit; Legislation, Food; Meat; Vegetables

Double-blind, placebo controlled challenge tests with benzoic acid butylhydroxytoluene, butylhydroxyanisole, beta-carotene, beta-8-apo-carotenal, and sodium metabisulfite were made in 44 cases of chronic urticaria, 91 cases of atopic dermatitis, and 123 cases of contact dermatitis, as a comparison group. Positive reactions were seen in four patients, two of whom had urticaria, one atopic dermatitis, and one contact dermatitis. Two of these reactions were caused by the placebo, one in a patient with urticaria and the other in a contact dermatitis patient. For one patient who reacted to the placebo and one who reacted to benzoic acid, the challenges were repeated with positive results in both instances. In nine patients, equivocal test results were produced with all the active substances and the placebo, but in all nine cases, retesting 4 days later produced negative results. This suggests that common food additives are seldom if ever of significance as precipitating factors in chronic urticaria or atopic dermatitis.

Topics: Adolescent; Adult; Aged; beta Carotene; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Carotenoids; Child; Child, Preschool; Dermatitis, Atopic; Dermatitis, Contact; Double-Blind Method; Female; Food Additives; Humans; Male; Middle Aged; Prospective Studies; Sulfites; Urticaria

Beta-carotene (BC) degradation was studied by liquid chromatography coupled to a quadrupole time of flight mass spectrometer. Throughout/After 21 days of dark storage, 56 nonvolatile degradants were chromatographically separated from pure BC crystal and their molecular formulas were identified. Their structure information was gained by comparing the fragments to a different, but structure-related compound. For example, a newly formed double bond position in dehydrogenated BC was determined by comparing the fragments between BC and dehydrogenated BC. One of their chemical structures was confirmed by comparing its precursor ion mass, retention time, isotopic ratio, and fragmentation to a pure trans-beta-apo-8'-apocarotenal. BC cleavage was observed on double bonds as well as single bonds in BC conjugation chain. PRACTICAL APPLICATION: As evidenced in this study, beta-carotene (BC) degradation is a spontaneous process initiated when the compound is exposed to air. The stoichiometric ratio of BC to oxygen is 1:0.03 at the first oxidation, therefore, only 0.3 mg oxygen or 1.2 mL air will degrade 10 mg BC, an average daily recommended intake. Not like in enzymatic BC degradation, spontaneous BC oxidation did not produce provitamin A, either in retina C20H38O or retinol C20H40O forms. For BC application in vitamin A deficiency, spontaneous BC oxidation should be avoided.

Topics: beta Carotene; Carotenoids; Mass Spectrometry; Molecular Structure; Oxidation-Reduction

Attaining defined steady-state carotenoid levels requires balancing of the rates governing their synthesis and metabolism. Phytoene formation mediated by phytoene synthase (PSY) is rate limiting in the biosynthesis of carotenoids, whereas carotenoid catabolism involves a multitude of nonenzymatic and enzymatic processes. We investigated carotenoid and apocarotenoid formation in Arabidopsis (Arabidopsis thaliana) in response to enhanced pathway flux upon PSY overexpression. This resulted in a dramatic accumulation of mainly β-carotene in roots and nongreen calli, whereas carotenoids remained unchanged in leaves. We show that, in chloroplasts, surplus PSY was partially soluble, localized in the stroma and, therefore, inactive, whereas the membrane-bound portion mediated a doubling of phytoene synthesis rates. Increased pathway flux was not compensated by enhanced generation of long-chain apocarotenals but resulted in higher levels of C13 apocarotenoid glycosides (AGs). Using mutant lines deficient in carotenoid cleavage dioxygenases (CCDs), we identified CCD4 as being mainly responsible for the majority of AGs formed. Moreover, changed AG patterns in the carotene hydroxylase mutants lutein deficient1 (lut1) and lut5 exhibiting altered leaf carotenoids allowed us to define specific xanthophyll species as precursors for the apocarotenoid aglycons detected. In contrast to leaves, carotenoid hyperaccumulating roots contained higher levels of β-carotene-derived apocarotenals, whereas AGs were absent. These contrasting responses are associated with tissue-specific capacities to synthesize xanthophylls, which thus determine the modes of carotenoid accumulation and apocarotenoid formation.

Topics: Arabidopsis; Arabidopsis Proteins; beta Carotene; Carotenoids; Chloroplasts; Chromatography, Liquid; Dioxygenases; Geranylgeranyl-Diphosphate Geranylgeranyltransferase; Glycosides; Glycosylation; Homeostasis; Immunoblotting; Mass Spectrometry; Mutation; Plant Leaves; Plant Roots; Xanthophylls

Muskmelons, both cantaloupe (Cucumis melo Reticulatus Group) and orange-fleshed honeydew (C. melo Inodorus Group), a cross between orange-fleshed cantaloupe and green-fleshed honeydew, are excellent sources of β-carotene. Although β-carotene from melon is an important dietary antioxidant and precursor of vitamin A, its bioaccessibility/bioavailability is unknown. We compared β-carotene concentrations from previously frozen orange-fleshed honeydew and cantaloupe melons grown under the same glasshouse conditions, and from freshly harvested field-grown, orange-fleshed honeydew melon to determine β-carotene bioaccessibility/bioavailability, concentrations of novel β-apocarotenals, and chromoplast structure of orange-fleshed honeydew melon. β-Carotene and β-apocarotenal concentrations were determined by HPLC and/or HPLC-MS, β-carotene bioaccessibility/bioavailability was determined by in vitro digestion and Caco-2 cell uptake, and chromoplast structure was determined by electron microscopy. The average β-carotene concentrations (μg/g dry weight) for the orange-fleshed honeydew and cantaloupe were 242.8 and 176.3 respectively. The average dry weights per gram of wet weight of orange-fleshed honeydew and cantaloupe were 0.094 g and 0.071 g, respectively. The bioaccessibility of field-grown orange-fleshed honeydew melons was determined to be 3.2 ± 0.3%, bioavailability in Caco-2 cells was about 11%, and chromoplast structure from orange-fleshed honeydew melons was globular (as opposed to crystalline) in nature. We detected β-apo-8'-, β-apo-10', β-apo-12'-, and β-apo-14'-carotenals and β-apo-13-carotenone in orange-fleshed melons (at a level of 1-2% of total β-carotene). Orange-fleshed honeydew melon fruit had higher amounts of β-carotene than cantaloupe. The bioaccessibility/bioavailability of β-carotene from orange-fleshed melons was comparable to that from carrot (Daucus carota).

Topics: beta Carotene; Biological Availability; Caco-2 Cells; Carotenoids; Cucumis melo; Digestion; Fruit; Humans; Models, Biological

High dose beta-carotene supplementation of smokers was associated with increased lung cancer risk in two intervention trials. It was proposed that generation of apocarotenals in smoke-exposed lungs impaired retinoic acid (RA) signaling, leading to squamous metaplasia and cell proliferation. To test this, we compared RA target gene regulation by retinoids, apocarotenals or beta-carotene by transcriptomics in BEAS-2B cells cultured to promote squamous differentiation. Retinoids, beta-carotene as well as apocarotenals induced known RA target genes. Retinoids upregulated involucrin, indicating that retinoids did not rescue BEAS-2B cells from squamous differentiation. Muc5AC, a marker for mucous differentiation, was transiently induced. beta-Carotene and apocarotenals less strongly induced involucrin and did not induce muc5AC. In summary, apocarotenals or beta-carotene upregulated RA target genes suggesting promotion, not inhibition, of RA signaling in BEAS-2B cells. Furthermore, apocarotenals and beta-carotene regulated gene expression independently of RA signaling. Squamous differentiation is not unequivocally linked to RA deficiency in BEAS-2B cells.

Topics: beta Carotene; Bronchi; Carotenoids; Cell Differentiation; Cell Line; Chromatography, High Pressure Liquid; Cluster Analysis; Dose-Response Relationship, Drug; Epithelial Cells; Gene Expression; Gene Expression Profiling; Humans; Oligonucleotide Array Sequence Analysis; Retinoids; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Time Factors

beta-Carotene might be converted oxidatively to vitamin A- active products in animals by the following three possible routes: 1) central cleavage, 2) sequential excentric cleavage or 3) random cleavage. Central cleavage is strongly favored by stoichiometric studies with tissue homogenates in vitro. To examine the relative importance of these pathways in rats in vivo, an oral dose (5.6 micromol) of all-trans beta-carotene in oil was given to vitamin A-deficient (-A) and to vitamin A-sufficient (+A) adult female Sprague-Dawley rats. Serum and several tissues were analyzed before and 3 h after dosing. The primary products of beta-carotene found in the intestine, serum and liver were retinol, retinyl esters and retinoic acid. Two minor oxidation products of beta-carotene, namely, 5,6-epoxy-beta-carotene and a partially characterized hydroxy-beta-carotene, were present in the stomach and its contents as well as in intestinal preparations. In the intestine, including its contents, of -A rats, very minor amounts of 5,6-epoxyretinyl palmitate and of beta-apocarotenals (8', 10', 12', 14') were identified. The total amount of the beta-apocarotenoids, however, was <5% of the retinoids formed in the intestine from beta-carotene during the same period. Another beta-carotene derivative, with a spectrum similar to that of semi-beta-carotenone, citranaxanthin and beta-apo-6'-carotenal, was also found in the intestinal extract of a -A rat. beta-Apocarotenals, beta-apocarotenols, beta-apocarotenyl esters and beta-apocarotenoic acids were not detected in tissues of +A rats nor in other tissues of -A rats. These findings agree with the view that central cleavage is by far the major pathway for the formation of vitamin A from beta-carotene in healthy rats in vivo.

Topics: Animals; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Female; Gastric Mucosa; Intestine, Small; Liver; Rats; Rats, Sprague-Dawley; Retinaldehyde; Retinoids; Vitamin A Deficiency

To determine whether carotenoids can modulate xenobiotic-metabolizing enzymes in mice, catalytic activities of several phase I and phase II enzymes have been measured in liver microsomes and cytosol of male Swiss mice fed diets containing beta-carotene, beta-apo-8'-carotenal, canthaxanthin, or astaxanthin (300 mg/kg diet) or treated with 3-methylcholanthrene (3-MC) (3 times at 50 mg/kg ip) for 15 days. Canthaxanthin increased CYP 1A-dependent activities: ethoxyresorufin O-deethylase (EROD) was increased 3-fold, pentoxyresorufin dealkylase (PROD) was increased 2.5-fold, and methoxyresorufin O-demethylase (MROD) was increased 1.6-fold; these increases were much less than those induced by 3-MC, which induced EROD 49-fold, PROD 10-fold, and MROD 4-fold. 3-MC, but not canthaxanthin, also increased relative liver weight, liver P-450 content, NADH-cytochrome c reductase, and benzoxyresorufin dearylase. The three other carotenoids had little or no effect on phase I enzymes. Among the phase II enzyme activities, only NADPH-quinone reductase was slightly increased by 3-MC and carotenoids, except beta-carotene. Among the three carotenoids that have previously been found to be powerful CYP 1A inducers in the rat, i.e., canthaxanthin, astaxanthin, and beta-apo-8'-carotenal, only canthaxanthin shows some (weak) inducing effect of CYP 1A in the 3-MC-responsive Swiss mice, indicating that the mechanism of CYP 1A induction by carotenoids may not be the same as that by 3-MC. In addition, the fact that beta-carotene has no effect on the tested enzymes does not support the hypothesis that the modulation of xenobiotic metabolism is a possible mechanism for the antimutagenic and anticarcinogenic effects of beta-carotene, which have been demonstrated in several in vivo models in mice.

Topics: Animals; beta Carotene; Canthaxanthin; Carotenoids; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP2B1; Cytochrome P-450 Enzyme System; Cytosol; Enzyme Induction; Liver; Male; Methylcholanthrene; Mice; Microsomes, Liver; Oxidoreductases; Vitamin A; Xanthophylls; Xenobiotics

1. The catalytic activities of several phase I and II xenobiotic-metabolizing enzymes and their immunochemical detection have been investigated in liver microsomes and cytosol of the male rat, which had been fed for 15 days with diets containing 300 mg/kg beta-carotene isomers (all-trans beta-carotene or beta-carotene from Dunaliella salina rich in 9-cis isomer or isomerized beta-carotene), or apocarotenoids as beta-apo-8'-carotenal, ethyl beta-apo-8'-carotenoate and citranaxanthin. 2. Beta-carotene, either all-trans or containing cis isomers, did not induce any significant change in the measured activities. By contrast, beta-apo-8'-carotenal increased the liver content of cytochrome P450, the activity of NADH- and NADPH-cytochrome c reductase, and strongly increased some cytochrome P450-dependent activities, particularly ethoxyresorufin O-deethylase (x158), methoxyresorufin O-demethylase (x22), pentoxy- and benzoxyresorufin O-dealkylases, but did not affect erythromycin N-demethylase nor nitrosodimethylamine N-demethylase activities. Phase II p-nitrophenol- and 4-hydroxy- biphenyl-uridine diphosphoglucuronosyl transferase activities were also increased by beta-apo-8'carotenal. Western blots of microsomal proteins clearly showed the induction of CYP1A1 and 1A2 by beta-apo-8'-carotenal. This induction profile resembles that produced by two other carotenoids: canthaxanthin and astaxanthin. Ethyl beta-apo-8'-carotenoate and citranaxanthin showed similar effects to beta-apo-8'-carotenal but of less intensity. 3. Three carotenoids: beta-apo-8'-carotenal, canthaxanthin and astaxanthin, are inducers of CYP1A1 and 1A2 in the rat. These carotenoids form a new class of inducers of CYP1A, structurally very different from the classical inducers as 3-methylcholanthrene, beta-naphtoflavone or dioxin.

Topics: Animals; Antioxidants; beta Carotene; Body Weight; Canthaxanthin; Carotenoids; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1A2; Eating; Enzyme Induction; Liver; Male; Methylcholanthrene; Microsomes, Liver; NADPH-Ferrihemoprotein Reductase; Rats; Rats, Wistar

The anticarcinogenic action of carotenoids such as beta-carotene has been frequently ascribed to their antioxidant properties. However, very little is actually known about the nature of the antioxidant reaction or the products that are formed. beta-Carotene was exposed to either spontaneous autoxidation conditions or to radical-initiated autoxidation conditions. The products were separated by reverse-phase HPLC, and individual peaks were characterized with an on-line diode array detector. Carbonyl products were isolated and characterized by several procedures, including borohydride reduction to the corresponding alcohols, derivatization with O-ethyl-hydroxylamine to the corresponding O-ethyl-oximes of the carbonyls, and analysis by GC-MS. Under the conditions of the experiments, the formation of a homologous series of carbonyl products was demonstrated, including beta-apo-13-carotenone, retinal, beta-apo-14'-carotenal, beta-apo-12'-carotenal, and beta-apo-10'-carotenal. Several very hydrophobic compounds were formed, which have not been previously identified. In addition, the products of NaOCl-treatment of beta-carotene were analyzed, and shown to be significantly different from the autoxidation products. This type of product analysis should be useful in determining the nature of the oxidants reacting with beta-carotene in vivo.

Topics: Antioxidants; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Free Radicals; Kinetics; Mass Spectrometry; Oxidation-Reduction; Sodium Hypochlorite; Vitamin E

Whether the conversion of beta-carotene into retinoids involves an enzymatic excentric cleavage mechanism was examined in vitro with homogenates prepared from human, monkey, ferret, and rat tissue. Using high-performance liquid chromatography, significant amounts of beta-apo-12'-, -10'-, and -8'-carotenals, retinal, and retinoic acid were found after incubation of intestinal homogenates of the four different species with beta-carotene in the presence of NAD+ and dithiothreitol. No beta-apo-carotenals or retinoids were detected in control incubations done without tissue homogenates. The production of beta-apo-carotenals was linear for 30 min and up to tissue protein concentrations of 1.5 mg/ml. The rate of formation of beta-apo-carotenals from 2 microM beta-carotene was about 7- to 14-fold higher than the rate of retinoid formation in intestinal homogenates, and the rate of beta-apo-carotenal production was fivefold greater in primate intestine vs rat or ferret intestine (P less than 0.05). The amounts of beta-apo-carotenals and retinoids formed were markedly reduced when NAD+ was replaced by NADH, or when dithiothreitol and cofactors were deleted from the incubation mixture. Both beta-apo-carotenal and retinoid production from beta-carotene were inhibited completely by adding disulfiram, an inhibitor of sulfhydryl-containing enzymes. Incubation of beta-carotene with liver, kidney, lung, and fat homogenates from each species also resulted in the appearance of beta-apo-carotenals and retinoids. The identification of three unknown compounds which might be excentric cleavage products is ongoing. These data support the existence of an excentric cleavage mechanism for beta-carotene conversion.

Topics: Animals; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Disulfiram; Dithiothreitol; Ferrets; Haplorhini; Humans; Hydrogen-Ion Concentration; Male; NAD; Organ Specificity; Rats; Rats, Inbred Strains; Retinoids

The experiment was carried out on 50 slaughter cocks, aged 5 weeks. The purpose of the experiment was to estimate the effect of beta-carotene and apo-beta-carotenoic acid (10% Carophyll yellow) on some indices of cellular immunity in chicks receiving the feed of high vitamin A content. Chl and NBT proved that carotenoids increased phagocytic activity of neutrophiles in peripheral blood. Similarly, in the case of beta-carotene it was found by blastic transformation test that on 30-40th day of the experiment, the value IS of peripheral blood lymphocytes was increased. On the other hand, chicks fed apo-beta-carotenoic acid showed such an effect on 40th day of observation only in the case when the lowest dose of preparation (24 mg/kg of feed) and Con A as mitogen were applied. In each experimental group, the chicks exhibited increased flavin content in liver and markedly increased retinol content due to apo-beta-carotenoic acid (24 mg/kg of feed). On the other hand, the contents of alpha tocopherol and ascorbic acid did not show significant differences between experimental and control groups. Similar were the results with iron, zinc and magnesium. Copper content of the liver was markedly increased in the birds receiving apo-beta-carotenoic acid in the dose of 24 mg/kg of feed. The increased content of manganese was observed in the liver of birds receiving beta carotene (6 mg/kg of feed).

Topics: Adjuvants, Immunologic; Animal Feed; Animals; beta Carotene; Carotenoids; Chickens; Food, Fortified; Lymphocyte Activation; Male; Neutrophils; Phagocytosis; Vitamin A