Semisynthesis of Betaxanthins from Purified Betacyanin of Opuntia dillenii sp.: Color Stability and Antiradical Capacity.

The availability of pure individual betalains in sufficient quantities which permit deeper understanding is still a challenge. This study investigates the high-yielding semisynthesis of betaxanthins using betalamic acid from a natural source (Opuntia dillenii), followed by condensation with ʟ-amino acids and further purification. Moreover, the color stability of the four synthesized individual betaxanthins, namely proline (ʟ-ProBX), alanine (ʟ-AlaBX), leucine (ʟ-LeuBX), and phenylalanine (ʟ-PheBX) betaxanthins, was investigated at different pHs. Their relative contribution to free radical scavenging was also scrutinized by TEAC and DPPH. ʟ-AlaBX and ʟ-LeuBx showed a significantly (p < 0.05) higher antioxidant activity, whereas ʟ-ProBX was the most resistant to the hydrolysis of betaxanthin and hence the least susceptible to color change. The color stability was strongly influenced by pH, with the color of ʟ-ProBX, ʟ-LeuBX, and ʟ-AlaBX at pH 6 being more stable, probably due to the easier hydrolysis under acid conditions. The semisynthesis and purification allowed us to have available remarkable quantities of pure individual betaxanthins of Opuntia dillenii for the first time, and to establish their color properties and antioxidant capacity. This study could be a step forward in the development of the best natural food colorant formulation, based on the betalain structure, which is of special interest in food technology.

pH-dependent stability of major betalains in the encapsulated beetroot extracts (Beta vulgaris L.).

Betalain is a water-soluble pigment contained in Caryophyllales plants. It not only holds potential as a natural food colorant but also offers various health benefits, acting as an antioxidant. This study focused on analyzing the pH-dependent stability of encapsulated betalain pigments extracted from red beetroot (Beta vulgaris L.) using methods such as absorption spectroscopy, HPLC, and LC-MS. The major pigments identified were vulgaxanthin I, betanin, isobetanin, and neobetanin, alongside minor components, including three betaxanthin species and a degradation product known as betalamic acid. Spectrophotometric analyses revealed that above pH 8, the betalain peak at 435 nm decreased and red-shifted to a peak at 549 nm, a shift that could be reversed through neutral pH treatment. At pH 11, a new broad peak appeared at 410 nm and was identified as betalamic acid. To assess the pH-dependency of each betalain, the targeted betalains were separated and quantified through HPLC after incubation across a wide pH range of 2-11 and during storage. After 3 days of storage in highly alkaline conditions (pH 10-11), major betalains, with the exception of neobetanin, underwent significant degradation. Conversely, these pigments displayed relative stability in acidic conditions. In contrast, neobetanin showed vulnerability to acidic conditions but exhibited tolerance to alkaline pH levels of 10-11. The degradation product, betalamic acid, demonstrated a similar susceptibility to alkaline pH as betanins. In conclusion, the significant stability decrease under highly alkaline conditions results not only from the hydrolytic reaction of betalains but also from the degradation of betalamic acid itself. PRACTICAL APPLICATION: Encapsulation methods are used to enhance the stability of betalains against temperature variations; however, the effects of pH, especially when considering individual betalain species, are not well understood. Despite betalains exhibiting similar features and being suitable for a wide pH range from acid to alkaline conditions, they are significantly affected by alkaline pH levels exceeding 10, as well as by storage duration. This study demonstrated the application of encapsulation to pH-dependent stability, and the findings offer valuable insights and a fresh perspective on betalains as red biocolorants, extending their potential application to a wide range of pH-controlled food products.

Leaf pigmentation, its profiles and radical scavenging activity in selected Amaranthus tricolor leafy vegetables.

The selected A. tricolor accessions contained abundant color attributes, betacyanin, carotenoids, betalains, betaxanthins, and antioxidants potentiality that varied in terms of genotypes. For the first time, we identified 4 betacyanins, and 5 carotenoid compounds in A. tricolor genotypes. The genotype VA14 and VA16 had abundant color attributes, betacyanin such as amaranthine, iso-amaranthine, betanin, iso-betanin, and antioxidants potentiality. These two genotypes having an excellent source of color attributes, betacyanins, betalains, betaxanthins, and antioxidants potentiality could be used as potent antioxidant varieties. The genotype VA11 and VA16 had abundant carotenoid components, such as zeaxanthin, lutein, violaxanthin, neoxanthin, total xanthophylls, and beta-carotene. The genotype VA11 and VA16 had abundant carotenoid components that could be used as carotenoid enrich varieties. It revealed from the correlation study that pigment profiles of A. tricolor genotypes exhibited high quenching capacity of radicals. These accessions have high antioxidant potentials and great opportunity to make drinks, preservatives, and colorant of food products to feed the community deficient in antioxidants. The identified components of betacyanins and carotenoids in A. tricolor require comprehensive pharmacological study. The baseline data on color attributes, betacyanins profile, carotenoids profile, betaxanthins, betalains and antioxidant potentiality obtained in the present study could contribute to pharmacologists for evaluating these components scientifically in A. tricolor.

Metabolic Engineering of Escherichia coli for de Novo Production of Betaxanthins.

Betalains are emerging natural pigments with high tinctorial strength and stability, physiological activities, and fluorescent properties for potential application in food, cosmetic, and pharmaceutical industries. Betalains including yellow betaxanthins and red betacyanins are mainly restricted in the Caryophyllales plants. To expand the availability of individual betaxanthins, here, we constructed an Escherichia coli BTA6 for de novo biosynthesis of betalamic acid. Using this strain as a monoculture platform, 14 yellow and 2 red betaxanthins were produced by feeding amino acids and amines. Furthermore, we constructed an l-histidine overproducing strain using chromosome engineering to deattenuate regulation and established a coculture system. After optimization of the initial inoculation ratios and fermentation conditions, the compatible and robust coculture system produced 287.69 mg/L of histidine-betaxanthin. This is the first report on de novo production of betaxanthins in engineered E. coli using glucose as a carbon source. Our work highlights the feasibility of microbial cell factories to produce individual betalains.

Indicaxanthin, a multi-target natural compound from Opuntia ficus-indica fruit: From its poly-pharmacological effects to biochemical mechanisms and molecular modelling studies.

Over the latest years phytochemical consumption has been associated to a decreased risk of both the onset and the development of a number of pathological conditions. In this context indicaxanthin, a betalain pigment from Opuntia ficus-indica fruit, has been the object of sound research. Explored, at first, for its mere antioxidant potential, Indicaxanthin is now regarded as a redox-active compound able to exert significant poly-pharmacological effects against several targets in a number of experimental conditions both in vivo and in vitro. This paper aims to provide an overview on the therapeutical effects of indicaxanthin, ranging from the anti-inflammatory to the neuro-modulatory and anti-tumoral ones and favored by its high bioavailability. Moreover, biochemical and molecular modelling investigations are aimed to identify the pharmacological targets the compound is able to interact with and to address the challenging development in the future research.

Advances and future directions in betalain metabolic engineering.

Betalains are nitrogenous red and yellow pigments found in a single order of plants, the Caryophyllales, and in some higher fungi. They are responsible for the colors observed in many ornamental plants, as well as in various food products, where they are used as natural colorants. Their nutritional properties and attractive colors make them an appealing target for metabolic engineering. This is further heightened by the limited availability of natural betalain sources, arising from their relative scarcity in the plant kingdom, particularly in edible plants. Recent progress in decoding their biosynthetic pathway has facilitated stable heterologous production of betalains in several plant and microbial systems. Here, we provide a brief review of recent advances and discuss current approaches and possible future directions in betalain metabolic engineering, including expanding the chemical diversity of betalains and increasing their yield, exploring new host organisms for their heterologous production, and engineering their secretion from the cell.

Indicaxanthin from Opuntia ficus indica (L. Mill) Inhibits Oxidized LDL-Mediated Human Endothelial Cell Dysfunction through Inhibition of NF-κB Activation.

Oxidized low-density lipoproteins (oxLDL) play a pivotal role in the etiopathogenesis of atherosclerosis through the activation of inflammatory signaling events eventually leading to endothelial dysfunction and senescence. In the present work, we investigated the effects of indicaxanthin, a bioavailable, redox-modulating phytochemical from Opuntia ficus indica fruits, with anti-inflammatory activity, against oxLDL-induced endothelial dysfunction. Human umbilical vein cord cells (HUVEC) were stimulated with human oxLDL, and the effects of indicaxanthin were evaluated in a range between 5 and 20 µM, consistent with its plasma level after a fruit meal (7 µM). Pretreatment with indicaxanthin significantly and concentration-dependently inhibited oxLDL-induced cytotoxicity; ICAM-1, VCAM-1, and ELAM-1 increase; and ABC-A1 decrease of both protein and mRNA levels. From a mechanistic perspective, we also provided evidence that the protective effects of indicaxanthin were redox-dependent and related to the pigment efficacy to inhibit NF-κB transcriptional activity. In conclusion, here we demonstrate indicaxanthin as a novel, dietary phytochemical, able to exert significant protective vascular effects in vitro, at nutritionally relevant concentrations.

Reverse screening on indicaxanthin from Opuntia ficus-indica as natural chemoactive and chemopreventive agent.

Indicaxanthin is a bioactive and bioavailable betalain pigment extracted from Opuntia ficus indica fruits. Indicaxanthin has pharmacokinetic proprieties, rarely found in other phytochemicals, and it has been demonstrated that it provides a broad-spectrum of pharmaceutical activity, exerting anti-proliferative, anti-inflammatory, and neuromodulator effects. The discovery of the Indicaxanthin physiological targets plays an important role in understanding the biochemical mechanism. In this study, combined reverse pharmacophore mapping, reverse docking, and text-based database search identified Inositol Trisphosphate 3-Kinase (ITP3K-A), Glutamate carboxypeptidase II (GCPII), Leukotriene-A4 hydrolase (LTA4H), Phosphoserine phosphatase (HPSP), Phosphodiesterase 4D (PDE4D), AMPA receptor (GluA3 and GluA2 subunits) and Kainate receptor (GluK1 isoform) as potential targets for Indicaxanthin. These targets are implicated in neuromodulation, and inflammatory regulation, normally expressed mostly in the CNS, and expressed (or overexpressed) in cancer tissues (i.e. breast, thyroid, and prostate cancer cells). Moreover, this study provides qualitative and quantitative information about dynamic interactions of Indicaxanthin at the binding site of target proteins, through molecular dynamics simulations and MM-GBSA.

Betaxanthin-Rich Extract from Cactus Pear Fruits as Yellow Water-Soluble Colorant with Potential Application in Foods.

Cactus pear (Opuntia ficus-indica) fruit juice is a source of betaxanthin pigments which can be used as a natural yellow food colorant. The HPLC chromatographic pigment pattern corresponding to the betaxanthin-rich extract revealed the presence of four betaxanthins, of which indicaxanthin (proline-betaxanthin) accounts for around 85%. A betaxanthin-rich water-soluble food colorant from cactus pears fruits was produced by spray-drying microencapsulation using maltodextrin as a wall material. The resulting powder was characterized by scanning electron microscopy, and its apparent color was analyzed by spectrometry. The stability of the microcapsules was examined at +20, +4 and -20 °C in the dark during six months of storage. The degradation of betaxanthins was delayed by microencapsulation and their colorant stability increased at lower temperatures. The potential application of the colorant microcapsules was successfully assessed in two food model systems: a yogurt and a soft-drink. Both foods presented an attractive pale yellow color. Pigment retention and color parameters were investigated during storage under controlled conditions. Slight changes in the pigment retention, in both model systems, pointed to excellent preservation in the dark, even after 28 days at 4 °C. However, the presence of light contributed to betaxanthin deterioration. Spray-drying microencapsulation succeeds in reducing volumen of the pigment extract and can be easy in storage and delivery of the powders. It is proved to be a suitable process that can be recommended for stabilizing betaxanthins from cactus pears to be used as water-soluble natural colorants in foods.

Stability of spray-dried beetroot extract using oligosaccharides and whey proteins.

The properties and stability of spray-dried beetroot extract using maltodextrin (MD), inulin (IN), and whey protein isolate (WPI) as carrier agents were evaluated. The values of moisture, betalains content, and retention were 3.33-4.24%, 348.79-385.47 mg/100 g (dry-basis), and 88.45-95.69%, respectively. Higher values of antioxidant activity were observed for the treatments using WPI. The treatment with inulin alone presented higher hygroscopicity in the moisture adsorption isotherms at 25 °C and lower thermal stability when evaluating the thermogravimetric curves. When stored at 60 °C, the use of WPI alone conferred lower stability to the beetroot extract powder. In general, the simultaneous use of IN and WPI as carrier agents resulted in good stability of the beetroot extract powder, representing an opportunity for innovation in food products.

Betaxanthins and antioxidant capacity in Stenocereus pruinosus: Stability and use in food.

Betalains are important pigments for the food, pharmaceutical, and cosmetics industry. In the yellow Stenocereus pruinosus fruits (pitayas), total betalain concentration, Folin-Ciocalteu reduction capacity, and antiradical capacity per dry weight were 2345.9µgg-1, 7.3mg gallic acid equivalentsg-1, and 48.8µmol Trolox equivalentg-1, respectively. The stability of betaxanthins, which represent 89% of total betalains in yellow pitayas, was evaluated over a range of pH, temperature, as well as in the presence of food additives. Maximum stability was observed at pH6.6, and addition of ascorbic acid increased the half-life 1.8 times. Thermal stability at pH6.48±0.05 was also evaluated from 50°C to 80°C, over which the activation energy for betaxanthin degradation was determined to be 66.2kJmol-1. Model gelatin gummies and beverages were then prepared with pitaya juice or pulp, and pigment retention and color parameters were investigated during storage under various conditions. To match the yellow color of commercial products, gummies were supplemented with 4.6% w/w juice or pulp, and beverages were supplemented with 5% w/v juice, achieving H° values of 69.0-86.2° and 64.6-87.1°, respectively. Results indicate that betaxanthins were more stable in gummies than in beverages, and that pigment retention increased when products were stored in the dark or at low temperatures. Also, different changes in color during storage were observed between gummies and beverages.

Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods.

There is a great interest in natural yellow colorants due to warnings issued about certain yellow food colorings of synthetic origin. However, no comparative studies have been reported of their thermal stability. For this reason, the thermal stabilities of six natural yellow colorants used in foods--lutein, riboflavin, curcumin, ß-carotene, gardenia yellow and Opuntia betaxanthins--were studied in simple solutions over a temperature range 30-90 °C. Spectral properties and visual color were investigated during 6 h of heat treatment. Visual color was monitored from the CIEL*a*b* parameters. The remaining absorbance at maximum wavelength and the total color difference were used to quantify color degradation. The rate of color degradation increased as the temperature rose. The results showed that the thermal degradation of the colorants followed a first-order reaction kinetics. The reaction rate constants and half-life periods were determined as being central to understanding the color degradation kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. Activation energies ranged from 3.2 kJmol(-1) (lutein) to 43.7 kJmol(-1) (Opuntia betaxanthins). ß-carotene and lutein exhibited high thermal stability, while betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin were in an intermediate position.

Plant betalains: Chemistry and biochemistry.

Betalains are vacuolar pigments composed of a nitrogenous core structure, betalamic acid [4-(2-oxoethylidene)-1,2,3,4-tetrahydropyridine-2,6-dicarboxylic acid]. Betalamic acid condenses with imino compounds (cyclo-l-3,4-dihydroxy-phenylalanine/its glucosyl derivatives), or amino acids/derivatives to form variety of betacyanins (violet) and betaxanthins (yellow), respectively. About 75 betalains have been structurally unambiguously identified from plants of about 17 families (known till date) out of 34 families under the order Caryophyllales, wherein they serve as chemosystematic markers. In this review, all the identified betalain structures are presented with relevant discussion. Also, an estimated annual production potential of betalains has been computed for the first time. In addition, mutual exclusiveness of anthocyanins and betalains has been discussed in the wake of new evidences. An inclusive list of betalain-accumulating plants reported so far has been presented here to highlight pigment occurrence and accumulation pattern. Betalain synthesis starts with hydroxylation of tyrosine to DOPA, and subsequent cleavage of aromatic ring of DOPA resulting to betalamic acid formation. This pathway consists of two key enzymes namely, bifunctional tyrosinase (hydroxylation and oxidation) and DOPA dioxygenase (O2-dependent aromatic ring cleavage). Various spontaneous cyclisation, condensation and glucosylation steps complement the extended pathway, which has been presented here comprehensively. The biosynthesis is affected by various ecophysiological factors including biotic and abiotic elicitors that can be manipulated to increase pigment production for commercial scale extraction. Betalains are completely safe to consume, and contribute to health.

Effect of extrusion cooking on bioactive compounds in encapsulated red cactus pear powder.

Red cactus pear has significant antioxidant activity and potential as a colorant in food, due to the presence of betalains. However, the betalains are highly thermolabile, and their application in thermal process, as extrusion cooking, should be evaluated. The aim of this study was to evaluate the effect of extrusion conditions on the chemical components of red cactus pear encapsulated powder. Cornstarch and encapsulated powder (2.5% w/w) were mixed and processed by extrusion at different barrel temperatures (80, 100, 120, 140 °C) and screw speeds (225, 275, 325 rpm) using a twin-screw extruder. Mean residence time (trm), color (L*, a*, b*), antioxidant activity, total polyphenol, betacyanin, and betaxanthin contents were determined on extrudates, and pigment degradation reaction rate constants (k) and activation energies (Ea) were calculated. Increases in barrel temperature and screw speed decreased the trm, and this was associated with better retentions of antioxidant activity, total polyphenol, betalain contents. The betacyanins k values ranged the -0.0188 to -0.0206/s and for betaxanthins ranged of -0.0122 to -0.0167/s, while Ea values were 1.5888 to 6.1815 kJ/mol, respectively. The bioactive compounds retention suggests that encapsulated powder can be used as pigments and to provide antioxidant properties to extruded products.

Pro-oxidant activity of indicaxanthin from Opuntia ficus indica modulates arachidonate metabolism and prostaglandin synthesis through lipid peroxide production in LPS-stimulated RAW 264.7 macrophages.

Macrophages come across active prostaglandin (PG) metabolism during inflammation, shunting early production of pro-inflammatory towards anti-inflammatory mediators terminating the process. This work for the first time provides evidence that a phytochemical may modulate the arachidonate (AA) metabolism in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, promoting the ultimate formation of anti-inflammatory cyclopentenone 15deoxy-PGJ2. Added 1 h before LPS, indicaxanthin from Opuntia Ficus Indica prevented activation of nuclear factor-κB (NF-κB) and over-expression of PGE2 synthase-1 (mPGES-1), but up-regulated cyclo-oxygenase-2 (COX-2) and PGD2 synthase (H-PGDS), with final production of the anti-inflammatory cyclopentenone. The effects were positively related with concentration between 50 and 100 µM. Indicaxanthin did not have any effect in the absence of LPS. A kinetic study investigating the redox status of LPS-stimulated macrophages between 0.5 and 12 h, either in the absence or in the presence of 50-100 µM indicaxanthin, revealed a differential control of ROS production, with early (0.5-3 h) modest inhibition, followed by a progressive (3-12 h) concentration-dependent enhancement over the level induced by LPS alone. In addition, indicaxanthin caused early (0.5-3 h) concentration-dependent elevation of conjugated diene lipid hydroperoxides, and production of hydroxynonenal-protein adducts, over the amount induced by LPS. In LPS-stimulated macrophages indicaxanthin did not affect PG metabolism when co-incubated with either an inhibitor of NADPH oxidase or vitamin E. It is concluded that LPS-induced pro-oxidant activity of indicaxanthin at the membrane level allows formation of signaling intermediates whose accumulation modulates PG biosynthetic pathway in inflamed macrophages.

Anti-proliferative and pro-apoptotic activity of whole extract and isolated indicaxanthin from Opuntia ficus-indica associated with re-activation of the onco-suppressor p16(INK4a) gene in human colorectal carcinoma (Caco-2) cells.

Phytochemicals may exert chemo-preventive effects on cells of the gastro-intestinal tract by modulating epigenome-regulated gene expression. The effect of the aqueous extract from the edible fruit of Opuntia ficus-indica (OFI extract), and of its betalain pigment indicaxanthin (Ind), on proliferation of human colon cancer Caco-2 cells has been investigated. Whole extract and Ind caused a dose-dependent apoptosis of proliferating cells at nutritionally relevant amounts, with IC50 400±25 mg fresh pulp equivalents/mL, and 115±15 µM (n=9), respectively, without toxicity for post-confluent differentiated cells. Ind accounted for ∼80% of the effect of the whole extract. Ind did not cause oxidative stress in proliferating Caco-2 cells. Epigenomic activity of Ind was evident as de-methylation of the tumor suppressor p16(INK4a) gene promoter, reactivation of the silenced mRNA expression and accumulation of p16(INK4a), a major controller of cell cycle. As a consequence, decrease of hyper-phosphorylated, in favor of the hypo-phosphorylated retinoblastoma was observed, with unaltered level of the cycline-dependent kinase CDK4. Cell cycle showed arrest in the G2/M-phase. Dietary cactus pear fruit and Ind may have chemo-preventive potential in intestinal cells.

Investigation of silent information regulator 1 (Sirt1) agonists from Traditional Chinese Medicine.

Silent information regulator 1 (Sirt1), a class III nicotinamide adenine dinucleotide dependent histone deacetylases, is important in cardioprotection, neuroprotection, metabolic disease, calorie restriction, and diseases associated with aging. Traditional Chinese Medicine (TCM) compounds from TCM Database@Taiwan ( http://tcm.cmu.edu.tw/ ) were employed for screening potent Sirt1 agonists, and molecular dynamics (MD) simulation was implemented to simulate ligand optimum docking poses and protein structure under dynamic conditions. TCM compounds such as (S)-tryptophan-betaxanthin, 5-O-feruloylquinic acid, and RosA exhibited good binding affinity across different computational methods, and their drug-like potential were validated by MD simulation. Docking poses indicate that the carboxylic group of the three candidates generated H-bonds with residues in the protein chain from Ser441 to Lys444 and formed H-bond, π-cation interactions, or hydrophobic contacts with Phe297 and key active residue, His363. During MD, stable π-cation interactions with residues Phe273 or Arg274 were formed by (S)-tryptophan-betaxanthin and RosA. All candidates were anchored to His363 by stable π- or H-bonds. Hence, we propose (S)-tryptophan-betaxanthin, 5-O-feruloylquinic acid, and RosA as potential lead compounds that can be further tested in drug development process for diseases associated with aging An animated interactive 3D complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:28.

Trans-epithelial transport of the betalain pigments indicaxanthin and betanin across Caco-2 cell monolayers and influence of food matrix.

PURPOSE: This study investigated the absorption mechanism of the phytochemicals indicaxanthin and betanin and the influence of their food matrix (cactus pear and red beet) on the intestinal transport. METHODS: Trans-epithelial transport of dietary-consistent amounts of indicaxanthin and betanin in Caco-2 cell monolayers seeded on Transwell(R) inserts was measured in apical to basolateral (AP-BL) and basolateral to apical (BL-AP) direction, under an inwardly directed pH gradient (pH 6.0/7.4, AP/BL) mimicking luminal and serosal sides of human intestinal epithelium. The effect of inhibitors of membrane transporters on the absorption was also evaluated. Contribution of the paracellular route was investigated after EDTA treatment of the cell monolayer. In vitro digestion of betalainic food was performed to provide a post-intestinal fraction containing bioaccessible pigments. RESULTS: Apparent permeability coefficients (P(app)) in the absorptive direction were (4.4 ± 0.4) × 10⁻6 and (3.2 ± 0.3) × 10⁻6 cm s⁻¹ for indicaxanthin and betanin, respectively. Transport of indicaxanthin was non-polarized, linear as a function of time and concentration, and unaffected by inhibitors of membrane transporters. Betanin exhibited significantly different bidirectional P(app) values and non-linear efflux kinetics. The concentration-dependent betanin efflux was described by a kinetic model including one non-saturable (K(d) = 0.042 µL cm⁻² min⁻¹) and one saturable component identified as the apical multidrug resistance-associated protein 2 (MRP2; K(m) = 275 µM; J(max) = 42 pmol min⁻¹ cm⁻²). Permeation of both betalains increased remarkably after EDTA treatment of the cell monolayer. Neither indicaxanthin nor betanin underwent metabolic transformation. Food matrix did not affect trans-epithelial transfer of indicaxanthin, but reduced the absorption rate of betanin, red beet more than cactus pear. CONCLUSIONS: Dietary indicaxanthin and betanin can substantially be absorbed through paracellular junctions of intestinal epithelial cells. Additional trans-membrane permeation can be considered for betanin, whose absorption is limited by a MRP2-mediated efflux and negatively affected by its food matrix. Present findings are consistent with the quite higher bioavailability of indicaxanthin over betanin established in humans.

In vitro synthesis of betaxanthins using recombinant DOPA 4,5-dioxygenase and evaluation of their radical-scavenging activities.

Betalamic acid, the chromophore of betaxanthins, was enzymatically synthesized on a large scale from l-dihydroxyphenylalanine (L-DOPA) using recombinant Mirabilis jalapa DOPA 4,5-dioxygenase. After synthesis, proline was directly added to the concentrated reaction mixture to generate proline-betaxanthin. The molecular mass and nuclear magnetic resonance spectrum of the purified product were identical to those previously reported for proline-betaxanthin. Twenty-four betaxanthin species were synthesized by the condensation reaction of purified betalamic acid and amino acids or amines. An HPLC protocol was established for identifying the different betaxanthin species. Proline-, dopamine-, and γ-aminobutyric acid (GABA)-betaxanthins were prepared as representative betaxanthins under large-scale conditions, and their 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities were compared against those of known antioxidants. GABA-betaxanthin showed comparatively low activity, whereas dopamine-betaxanthin had similar activity to the red pigment betanin and the anthocyanin cyanidin 3-glucoside. Proline-betaxanthin had the highest activity of the three synthesized compounds and was similar to the flavonoid quercetin.