Absence Of Ascorbic Acid Research Articles

Construction of a Double Z‐Scheme CuO/Cu2O/CuS/ZnO Quaternary Heterojunction Photocatalyst with Enhanced Solar‐Driven Photocatalytic Performance for Sulfamethoxazole Degradation

AbstractA novel CuO/Cu2O/CuS/ZnO quaternary heterojunction photocatalyst was constructed through a facile microwave technique. The structure, morphology and optical properties were characterized and explored. The photocatalytic activity of CuO/Cu2O/CuS/ZnO quaternary composite was assessed by antibiotic sulfamethoxazole under the simulated solar light irradiation. The quaternary composite manifested more excellent photocatalytic performance than the pristine ZnS and CuO/Cu2O. Moreover, the effects of ascorbic acid concentration on removal efficiency of sulfamethoxazole were discussed, revealing the importance of Cu2O in sulfamethoxazole removal. Particularly, as the ascorbic acid was 0.50 M, the total removal efficiency of sulfamethoxazole at an initial concentration of 20 mg/L was approximately 99.17 %, and the fitted pseudo‐first‐order kinetic rate constant reached 0.0380/min, which were 1.73 and 6.91 times of that in the absence of ascorbic acid, respectively. A double Z‐scheme charge transfer mechanism was confirmed by the reactive species trapping tests, which demonstrated that superoxide radicals and holes were the major reactive species responsible for sulfamethoxazol degradation. CuO/Cu2O/CuS/ZnO nanocomposite provided an interesting perspective for a highly efficient quaternary photocatalyst that could be employed for remediation antibiotics.

Tolerance to desiccation and freezing of Passiflora alata Curtis cv BRS Mel do Cerrado seeds and pre-germination treatments

To define the best storage conditions, it is necessary to know the physiological behavior of the seeds. The objectives of this study was to evaluate the physiological quality of seeds of Passiflora alata Curtis cultivar “BRS Mel do Cerrado” with different water contents and frozen at -20 °C. The effect of pre-germination treatments on seed performance after drying and freezing was also evaluated. Seeds dried until water content of 12.6%, 7.6%, 5.5%, 4.9%, 4.5%, 4.3%, 3.8% and undried seeds (control) with 19.2% moisture were stored at -20 ºC for 100 days. Germination and vigor tests (germination speed index, GSI) were carried out on dried seeds in the presence or absence of a growth regulator (gibberellins + cytokinins) and on frozen seeds, in the presence or absence of ascorbic acid. Seed germination after drying was high, ranging from 78% to 94%, regardless of the use of the growth regulator. Different results were observed for vigor, since greater germination speed was observed in treated seeds. The freezing did not affect germination and vigor of seeds with moisture ≤7.6%, unlikely of frozen with high moisture seeds, which did not germinate. Seeds of BRS Mel do Cerrado cultivar tolerate desiccation at low water contents and do not tolerate freezing at high moisture levels of 19.2% and 12.6%. Ascorbic acid does not increase the germination and vigor of dry and frozen seeds with differents moistures.

High performance Pt-anchored MoS2 based chemiresistive ascorbic acid sensor

Ascorbic acid (AA), known as vitamin C, is a vital bioactive compound that plays a crucial role in several metabolic processes, including the synthesis of collagen and neurotransmitters, the removal of harmful free radicals, and the uptake of iron by cells in the human intestines. As a result, there is an absolute need for a highly selective, sensitive, and economically viable sensing platform for AA detection. Herein, we demonstrate a Pt-decorated MoS2 for efficient detection of an AA biosensor. MoS2 hollow rectangular structures were synthesized using an easy and inexpensive chemical vapor deposition approach to meet the increasing need for a reliable detection platform. The synthesized MoS2 hollow rectangular structures are characterized through field effect scanning electron microscopy (FESEM), energy-dispersive spectroscopy elemental mapping, Raman spectroscopy, and x-ray photoelectron spectroscopy. We fabricate a chemiresistive biosensor based on Pt-decorated MoS2 that measures AA with great precision and high sensitivity. The experiments were designed to evaluate the response of the Pt-decorated MoS2 biosensor in the presence and absence of AA, and selectivity was evaluated for a variety of biomolecules, and it was observed to be very selective towards AA. The Pt-MoS2 device had a higher response of 125% against 1 mM concentration of AA biomolecules, when compared to that of all other devices and 2.2 times higher than that of the pristine MoS2 device. The outcomes of this study demonstrate the efficacy of Pt-decorated MoS2 as a promising material for AA detection. This research contributes to the ongoing efforts to enhance our capabilities in monitoring and detecting AA, fostering advancements in environmental, biomedical, and industrial applications.

Production of phenolic compounds from in vitro shoots of sugarcane (Saccharum spp.) in temporary immersion bioreactors

An alternative way to obtain molecules of high-value from plant origin for the agricultural and pharmaceutical industries is via the production of secondary metabolites from in vitro systems. Among these molecules are phenolic compounds that are important in plant defense system against biotic and abiotic factors. The objective of this work was to establish the culture conditions for the production and scaling up of phenolic compounds from sugarcane shoots produced in Temporary Immersion Bioreactors (TIBs). Two different sucrose concentrations and three inoculum densities of shoots per flask were tested for two sugarcane cultivars C86-56 and C1015-73. These cultivars were micropropagated in TIBs without ascorbic acid for phenolic compound production during 25 days, and were measured every five days. The best established conditions were evaluated on a pilot scale with ten TIBs for three sugarcane cultivars (C86-56, C1051-73 and C87-51). Although phenolic compounds were produced under all conditions evaluated at the experimental level, the most important production was achieved by using 15 shoots per vessel with 20 g.L-1 of sucrose in the absence of ascorbic acid after 25 days of culture. Cultivar C1051-73 had a higher multiplication coefficient independently of the treatments; this effect was not only significant for the phenolic compound production, but also for biomass increases. With respect to the pilot experiment, significant differences were detected for phenolic compound production among the three cultivars with C1051-73 showing the highest yield (23.05 mg.L-1). The results revealed that TIBs are a useful method to produce phenolic compounds with optimum yields.

Recirculating bioavailable nicotine metabolite using ascorbic acid: A pragmatic approach for treating nicotine dependence

Nicotine undergoes metabolism, converting into the oxidized metabolite cotinine, which can persist in the body for several weeks and potentially lead to fatal conditions, such as cancer. Conventional nicotine replacement therapy provides additional nicotine to the body, thereby increasing the chance of accumulating the toxic metabolite cotinine. Consequently, we proposed a hypothesis: converting cotinine back into nicotine using a suitable reducing agent, such as ascorbic acid, could be a practical approach. This conversion would allow cotinine to be reutilized for its central nervous system effects before its eventual elimination from the body. In the current study, we examined this hypothesis by using plasma samples from smokers. Volunteers (both non-smokers and smokers) were screened and recruited for this study. In the initial time- and dose-dependent studies, we incubated plasma samples from non-smokers with cotinine and ascorbic acid. Changes in cotinine and nicotine levels were quantified using HPLC-PDA. Based on the findings of these experiments, we selected a concentration of 1 µM ascorbic acid and incubated it with plasma samples from 25 smokers for 10 min. A time-dependent study revealed that nicotine was detected in non-smokers' plasma samples after a 10-minute incubation with 28.38 µM of both cotinine and ascorbic acid. In a subsequent dose-dependent study, the maximum concentration of nicotine was observed at 1 µM ascorbic acid. Among the 25 samples of smokers’ plasma, the mean nicotine concentration increased from 0.565 ± 0.196 to 1.937 ± 0.622 µM (P = 0.0081), while cotinine levels decreased from 1.278 ± 0.253 to 0.754 ± 0.137 µM (P = 0.0087). This study conclusively demonstrated that ascorbic acid, at a specified concentration, effectively converts cotinine back into nicotine in smokers' plasma. Importantly, this conversion did not occur in water or in the absence of ascorbic acid in the plasma, indicating enzyme involvement.

Antioxidant Interactions between Citrus Fruit Carotenoids and Ascorbic Acid in New Models of Animal Cell Membranes.

The regular consumption of citrus fruits by humans has been associated with lower incidence of chronic-degenerative diseases, especially those mediated by free radicals. Most of the health-promoting properties of citrus fruits derive from their antioxidant content of carotenoids and ascorbic acid (ASC). In the current work we have investigated the scavenging (against hydroxyl radical) and quenching capacities (against singlet oxygen) of four different carotenoid extracts of citrus fruits in the presence or absence of ASC (μM range) in organic solvent, aqueous solution, micelles and in an innovative biomimicking liposomal system of animal cell membrane (AML). The fruits of four varieties of citrus were selected for their distinctive carotenoid composition (liquid chromatography characterization): 'Nadorcott' mandarin and the sweet oranges 'Valencia late', 'Ruby Valencia' and 'Pinalate' mutant. The quenching activity of citrus carotenoids strongly depended on the biological assemblage: freely diffusible in organic solvent, 'Ruby Valencia' carotenoids (containing lycopene) showed the highest quenching activity, whereas 'Nadorcott' mandarin extracts, rich in β-cryptoxanthin, prevailed in micellar systems. Interestingly, the addition of 10 μM ASC significantly increased the quenching activity of all citrus extracts in micelles: 'Valencia' orange (+53%), 'Pinalate' (+87%), 'Ruby' (4-fold higher) and 'Nadorcott' mandarins (+20%). Accurate C11-BODIPY581/591 fluorescence assays showed solid scavenging activities of all citrus extracts against AML oxidation: 'Valencia' (-61%), 'Pinalate' (-58%) and 'Ruby' oranges (-29%), and 'Nadorcott' mandarins (-70%). Indeed, all four citrus extracts tested here have balanced antioxidant properties; extracts from the 'Nadorcott' mandarin slightly prevailed overall, due, at least in part, to its high content of β-cryptoxanthin. This study depicts some of the antioxidant interactions between citrus fruit carotenoids and ascorbic acid in models of animal cell membranes and reinforces the contribution of them in promoting health benefits for humans.

Mechanism of off-color formation in potato chips fried in oil systems containing ascorbic acid as a stabilizer

The use of alternative, green antioxidant (AOX) systems is demanded by consumers. Natural AOX systems pose significant challenges. For example, in frying applications, these AOX can negatively alter potato chip color, one of the most important traits in consumer selection. We evaluated the role of natural AOX systems containing ascorbic acid, tocopherols, and other antioxidants in amino acid-related undesirable color formation in fried potato chips. Results indicated that both oil phase AOX and potato factors are critical to generation of off-color formation in fried potato chips through Maillard type reactions. Ascorbic acid solubilization in oil and migration to the chip surface play key roles in observed off-color formation. However, multiple complex reactions may be responsible for color development, which may involve food matrix components. Contributions of AOX other than ascorbic acid appear minimal. Nevertheless, some browning can occur regardless of the presence of ascorbic acid. Color formation through glutamine occurred in the absence of ascorbic acid, but its presence greatly exacerbates color generation, while color generation via asparagine is barely modulated by ascorbic acid. AOX and free amino acid concentrations, temperature, and moisture are critical factors for controlling undesirable color formation during frying with natural oil AOX systems.

Roles of Two F-Box Proteins: FBXL14 in the Periosteum and FBXW2 at Elastic Fibers

I previously reported that F-box/leucine-rich repeat protein 14 (FBXL14) expressed in periosteum-derived cells, and F-box and WD-40 domain-containing protein 2 (FBXW2) in the periosteum form a fiber-like structure. Here, two culture medium conditions, that is, media with and without ascorbic acid, were compared during explant culture. In the absence of ascorbic acid, the expression patterns of osteocalcin, FBXW2, and elastin were compared using fluorescent immunostaining during weeks 3–5. By observing the periosteum, cambium layer and bone, I demonstrated FBXL14 expression in micro-vessels and bone lacuna. Fluorescent immunostaining revealed that, without ascorbic acid, the FBXL14 layer was thin. Conversely, in the presence of ascorbic acid, FBXL14 formed a thick membrane-like structure inside the periosteum, and the multilayer of periosteum-derived cells (PDCs) was strong. The expression patterns of osteocalcin and FBXW2 were similar. Elastin retained its fiber structure for up to five weeks. Although osteocalcin and FBXW2 were expressed in regions similar to elastin, they could not retain their fiber structures. In conclusion, FBXL14 appears to play a role in preparing a native scaffold for forming a multilayered sheet of PDCs inside the periosteum. FBXW2 and osteocalcin appear to separate from elastic fibers during calcification.

Enhanced osteogenic gene expressions and alkaline phosphatase activity of the composites based on bioactive glass and CuAl LDH for bone tissue engineering

A novel form of nanocomposite based on bioactive glass (BG) and CuAl LDH has been devised and manufactured for the first time in this paper. The produced nanocomposites, BG@CuAl LDH and BG@CuAl LDH@RO, were employed to examine the ability of the alkaline phosphatase activity to regulate the expression of COL 1, OCN and RUNX2 (ALP) gene expressions. The role of leaf extracts (Rosmarinus officinalis [RO]) on enhanced osteogenic gene expression has been investigated. Also, the relative cell viability has been analyzed by MTT assay on the hBMSCs, HEK‐293 and PC12 cell lines after 24 and 48 hours of treatment. The results showed significantly increased gene expressions in different microenvironments, the presence and absence of ascorbic acid and low cytotoxicity towards different cell lines. In the case of the hBMSCs cell lines, the synthesized nanomaterials' cell attachment and proliferation findings proved completely successful.

Fe3+ opposes the 1,25(OH)2D3-induced calcium transport across intestinal epithelium-like Caco-2 monolayer in the presence or absence of ascorbic acid.

Although iron is an essential element for hemoglobin and cytochrome synthesis, excessive intestinal iron absorption—as seen in dietary iron supplementation and hereditary disease called thalassemia—could interfere with transepithelial transport of calcium across the intestinal mucosa. The underlying cellular mechanism of iron-induced decrease in intestinal calcium absorption remains elusive, but it has been hypothesized that excess iron probably negates the actions of 1,25-dihydroxyvitamin D [1,25(OH)2D3]. Herein, we exposed the 1,25(OH)2D3-treated epithelium-like Caco-2 monolayer to FeCl3 to demonstrate the inhibitory effect of ferric ion on 1,25(OH)2D3-induced transepithelial calcium transport. We found that a 24-h exposure to FeCl3 on the apical side significantly decreased calcium transport, while increasing the transepithelial resistance (TER) in 1,25(OH)2D3-treated monolayer. The inhibitory action of FeCl3 was considered rapid since 60-min exposure was sufficient to block the 1,25(OH)2D3-induced decrease in TER and increase in calcium flux. Interestingly, FeCl3 did not affect the baseline calcium transport in the absence of 1,25(OH)2D3 treatment. Furthermore, although ascorbic acid is often administered to maximize calcium solubility and to enhance intestinal calcium absorption, it apparently had no effect on calcium transport across the FeCl3- and 1,25(OH)2D3-treated Caco-2 monolayer. In conclusion, apical exposure to ferric ion appeared to negate the 1,25(OH)2D3-stimulated calcium transport across the intestinal epithelium. The present finding has, therefore, provided important information for development of calcium and iron supplement products and treatment protocol for specific groups of individuals, such as thalassemia patients and pregnant women.

Profound architectural and functional readjustments of the secretory pathway in decidualization of endometrial stromal cells.

Certain cell types must expand their exocytic pathway to guarantee efficiency and fidelity of protein secretion. A spectacular case is offered by decidualizing human endometrial stromal cells (EnSCs). In the midluteal phase of the menstrual cycle, progesterone stimulation induces proliferating EnSCs to differentiate into professional secretors releasing proteins essential for efficient blastocyst implantation. Here, we describe the architectural rearrangements of the secretory pathway of a human EnSC line (TERT-immortalized human endometrial stromal cells (T-HESC)). As in primary cells, decidualization entails proliferation arrest and the coordinated expansion of the entire secretory pathway without detectable activation of unfolded protein response (UPR) pathways. Decidualization proceeds also in the absence of ascorbic acid, an essential cofactor for collagen biogenesis, despite also the secretion of some proteins whose folding does not depend on vitamin C is impaired. However, even in these conditions, no overt UPR induction can be detected. Morphometric analyses reveal that the exocytic pathway does not increase relatively to the volume of the cell. Thus, differently from other cell types, abundant production is guaranteed by a coordinated increase of the cell size following arrest of proliferation.

Copper-catalyzed ARGET ATRP of styrene from ethyl α-haloisobutyrate in EtOAc/EtOH, using ascorbic acid/Na2CO3 as reducing system

Atom transfer radical polymerization (ATRP) is one of the most powerful techniques to synthesize precisely tailored polymers and macrostructures. Activators regenerated by electron transfer (ARGET) ATRP was developed as a “green” strategy to decrease the load of the metal catalyst. However, ARGET ATRP usually uses not-so-green reducing agents (e.g. Sn2+) or expensive and industrially impractical procedures. For these reasons, we report an ARGET ATRP of styrene with various carbonates as reducing agents, both alone and paired with ascorbic acid (AA), using monofunctional initiators and Cl or Br as exchanging atoms. The solvent mixture is composed of the green combination of EtOAc and EtOH, even in the presence of modest amounts of H2O. Cyclic voltammetry was used to evaluate the effect of H2O on the catalyst, as well as the absence of AA. The system returned high yields and low dispersities with low amounts of catalyst (~60 ppm) and moderate reaction times. Excellent results were obtained only with the Cl-ATRP system. NMR spectroscopy and kinetic analyses proved the livingness of the final polymer chains.

Physicochemical properties of dihydromyricetin and the effects of ascorbic acid on its stability and bioavailability.

Dihydromyricetin (DMY) is a natural dihydroflavonol with many bioactive effects. However, the physicochemical properties of DMY related to its bioavailability, especially its stability, are unclear. The effects of pH, temperature, metal ions and ascorbic acid (AA) on the stability of DMY were studied using high-performance liquid chromatography (HPLC). The bioavailability of DMY in the presence and absence of AA was compared. Dihydromyricetin was unstable in weak alkaline solutions, and the degradation was significantly accelerated in the presence of Cu2+ and Fe3+ . The degradation process followed the first-order kinetic model. The degradation rate constant (k) increased with increasing pH and temperature. The remaining DMY was only 49% of its initial concnentration after 4h in simulated intestinal fluid (SIF) at 37 °C. However, by supplementing with AA, the degradation of DMY was rarely occured within 6h. The solubility of DMY at pH3-5 was about 750 μg mL-1 , slightly increasing to 853 μg mL-1 at pH6. Pharmacokinetic studies showed that the bioavailability of DMY increased from 0.122% to 0.341% by supplementing with AA (10% of DMY). The degradation of DMY is one reason for its poor bioavailability. The presence of AA could significantly improve the stability of DMY, and further improve its bioavailability in rats. © 2020 Society of Chemical Industry.

Collagen release by human hepatic stellate cells requires vitamin C and is efficiently blocked by hydroxylase inhibition.

Liver fibrosis is characterized by the accumulation of extracellular matrix proteins, mainly composed of collagen. Hepatic stellate cells (HSCs) mediate liver fibrosis by secreting collagen. Vitamin C (ascorbic acid) is a cofactor of prolyl-hydroxylases that modify newly synthesized collagen on the route for secretion. Unlike most animals, humans cannot synthesize ascorbic acid and its role in liver fibrosis remains unclear. Here, we determined the effect of ascorbic acid and prolyl-hydroxylase inhibition on collagen production and secretion by human HSCs. Primary human HSCs (p-hHSCs) and the human HSCscell line LX-2 were treated with ascorbic acid, transforming growth factor-beta (TGFβ) and/or the pan-hydroxylase inhibitor dimethyloxalylglycine (DMOG). Expression of collagen-I was analyzed by RT-qPCR (COL1A1), Western blotting, and immunofluorescence microscopy. Collagen secretion was determined in the medium by Western blotting for collagen-I and by HPLC for hydroxyproline concentrations. Expression of solute carrier family 23 members 1 and 2 (SLC23A1/SLC23A2), encoding sodium-dependent vitamin C transporters 1 and 2 (SVCT1/SVCT2) was quantified in healthy and cirrhotic human tissue. In the absence of ascorbic acid, collagen-I accumulated intracellularly in p-hHSCs and LX-2 cells, which was potentiated by TGFβ. Ascorbic acid co-treatment strongly promoted collagen-I excretion and enhanced extracellular hydroxyproline concentrations, without affecting collagen-I (COL1A1) mRNA levels. DMOG inhibited collagen-I release even in the presence of ascorbic acid and suppressed COL1A1 and alpha-smooth muscle actin (αSMA/ACTA2) mRNA levels, also under hypoxic conditions. Hepatocytes express both ascorbic acid transporters, while p-hHSCs and LX-2 express the only SVCT2, which is selectively enhanced in cirrhotic livers. Human HSCs rely on ascorbic acid for the efficient secretion of collagen-I, which can be effectively blocked by hydroxylase antagonists, revealing new therapeutic targets to treat liver fibrosis.

A copper complex formed with neurokinin B: binding stoichiometry, redox properties, self-assembly and cytotoxicity.

The tachykinin neuropeptide of neurokinin B (NKB) is a copper-binding amyloid peptide with important roles in the regulation of physiological functions and pathophysiological processes in the central and peripheral nervous systems. In this work, the formation of a NKB-Cu2+ complex in a 1 : 1 stoichiometry was confirmed by mass spectrometry. The self-assembly of NKB and its mutant species was investigated by Thioflavin T (ThT) fluorescence assay and atomic force microscopy (AFM), and at the same time, the effect of Cu2+ on the aggregation of NKB was studied. As evidenced by cyclic voltammetry, the redox potential of NKB-Cu2+ was determined to be 0.77 V (vs. Ag/AgCl). It has been demonstrated that NKB at low concentrations exerts its neuroprotective function by inhibiting Cu2+-mediated reactive oxygen species (ROS) production in the presence of ascorbic acid (AA). In comparison with equivalent Cu2+, the peptide-Cu2+ aggregates aggravated the viability of PC-12 cells more seriously in the absence of AA. These results should be extremely valuable for understanding the NKB/Cu2+ interactions and the toxicity mechanism of Cu2+ associated with neurodegenerative diseases.

Harnessing mesenchymal stem cell secretome: Effect of extracellular matrices on proangiogenic signaling.

The low engraftment and retention rate of mesenchymal stem cells (MSCs) at the target site indicates that the potential benefits of MSC-based therapies can be attributed to their paracrine signaling. In this study, the extracellular matrices (ECMs) deposited by bone marrow-derived human MSCs in the presence and absence of ascorbic acid was characterized. MSCs were seeded on top of decellularized ECM (dECM) and the concentrations of proangiogenic and antiangiogenic molecules released in culture (conditioned) media was compared. Effects of ECM derived from MSCs with different passage numbers on MSC secretome was also investigated. Our study revealed that the expression of proangiogenesis-related factors were upregulated when MSCs were harvested on dECMs, irrespective of media supplementation, as compared with those cultured on tissue culture plates. In addition, dECM generated in the presence of ascorbic acid promoted the expression of proangiogenic molecules as compared with dECM-derived in absence of media supplementation. Further, it was observed that the effectiveness of dECM to stimulate proangiogenic signaling of MSCs was reduced as cell passage number was increased from P3 to P5. The proliferation as well as capillary morphogenesis of human umbilical vein endothelial cells (HUVECs) in the presence of conditioned media were enhanced compared with the normal HUVECs culture media. These data indicate that the secretory signatures of MSCs and consequently, the therapeutic efficacy of MSCs can be regulated by presentation of dECM composition and variation of its composition.

Persulfate activation induced by ascorbic acid for efficient organic pollutants oxidation

In this study, we demonstrate that ascorbic acid (AA) exhibited extremely high activity on persulfate (PS) activation (AA/PS) to produce SO4− and OH for the degradation of various organic pollutants, including atrazine, pentachlorophenol, alachlor, tetracycline, and chloramphenicol. Taken atrazine as a model natural organic micropollutants, we surprisingly found that the degradation rate constant of atrazine during PS activation in presence of AA was about 29 times larger than that in the absence of AA. The underlying mechanism of persulfate activation induced by AA was then systematically investigated by electron spin resonance (ESR) analysis, theoretical density functional theory (DFT) calculations, and kinetic experiments. The combination of ESR and DFT results confirmed that the persulfate activation induced by ascorbic acid was attributed to the electron transfer from AA to PS. In this process, AA undergoes a two-step oxidation by PS to generate SO4− and dehydroascorbic acid with the formation of an intermediate ascorbate free radical. More interestingly, atrazine in the real aquifer sediment system could be totally oxidized in the presence of PS and AA. These findings offer a new economically feasible persulfate activation strategy for the in situ chemical oxidation of organic compounds in contaminated water and sediment systems.

Decolorization of Orange-G Aqueous Solutions over C60/MCM-41 Photocatalysts

The majority of the photocatalysts studied for azo-dye degradation are based on semiconductor materials. Studies reported on non-semiconducting materials are very scarce. In the present work, we studied the fullerene (C60) ability to accelerate photodegradation of the dye’s azo bond in the presence of ascorbic acid. A series of C60 supported on ordered mesoporous silica (MCM-41) catalysts, containing 1, 3, 6, 9, and 12 wt % of fullerene C60, was studied using Orange G (OG) as representative azo-dye. This study showed that partial decolorization is achieved in the dark by simple adsorption of the dye on the bare surface of the carrier. The extent of decolorization increases with the irradiation of the suspension due to photocatalytic degradation of the azo-bond. This is maximized over the sample containing 3 wt % of C60 and it has been attributed to the best combination of the extent of the dye adsorption with the high intrinsic photocatalytic activity of small C60 clusters predominated in this sample. This catalyst proved to be quite stable upon five subsequent photocatalytic cycles, losing less than 5% of its initial activity. No degradation of OG takes place in the absence of ascorbic acid.

Thermal and Photochemical Stability of Anthocyanins from Black Carrot, Grape Juice, and Purple Sweet Potato in Model Beverages in the Presence of Ascorbic Acid.

Anthocyanins are natural dyes widely used in the food industry, but their chemical stability in beverages can be affected by the presence of additives. In the present paper, the interaction between anthocyanins and ascorbic acid (AA) is more particularly investigated. Ascorbic acid is an ubiquitous component in food products. In this study, the thermal stability at 43 °C and the photolysis stability in air and in an inert atmosphere (N2) of anthocyanins extracted from black carrot (BC), grape juice (GJ), and purple sweet potato (SP) were studied in the presence and absence of ascorbic acid (in citrate buffer at pH 3). Discriminating the main environmental factors (i.e., heat and light) affecting anthocyanin stability is a key point for better understanding the degradation pathways. The stability of the anthocyanins was followed by UV-vis spectrometry. Moreover, to understand the degradation mechanisms in both the presence and absence of ascorbic acid, various techniques such as fluorescence quenching, cyclic voltammetry, and electron-spin-resonance (ESR) spectroscopy were also used to furnish a full coherent picture of the chemical mechanisms associated with the anthocyanin degradation. In addition, molecular orbitals and bond-dissociation energies (BDE) were calculated to extend the investigation. Moreover, the effects of some supplementary stabilizers (chlorogenic acid, sinapic acid, tannic acid, fumaric acid, β-carotene, isoquercitrin, myricitrin, green coffee bean extract, and rosemary extract) and sugars (sucrose, fructose, and glucose) on anthocyanins stability in the presence of ascorbic acid were examined.

A hybrid materialcomposed of guanine-rich single stranded DNA and cobalt(III) oxyhydroxide (CoOOH) nanosheets as a fluorescentprobe for ascorbic acid via formation of a complex between G-quadruplex and thioflavin T.

A hybrid material composed of guanine-rich single stranded DNA (G-rich ssDNA) and cobalt oxyhydroxide (CoOOH) nanosheets is used as a nanoprobe for fluorometric turn-on detection of ascorbic acid (AA). The CoOOH nanosheets function as a recognition component for AA. The G-rich ssDNA is used to produce a G-quadruplex, and the G-quadruplex/thioflavin T (ThT) complex acts as a fluorescent reporter. In the absence of AA, p-phenylenediamine (PPD) is oxidized to form oxPPD which has a dark red color. It causes the fluorescence of the G-quadruplex/ThT complex to be quenched. However, in the presence of AA, the CoOOH nanosheets of the nanoprobe are preferentially reduced by AA. Hence, PPD is not oxidized, and fluorescence is not quenched. A fluorometric turn-on method was developed based on these findings. It has a detection limit of 94nM and works in the concentration range from 1 to 10 and 20 to 80μM. This method was applied to the determination of AA in (spiked) fruit juice samples. Graphical abstract Schematic presentation of a fluorescent assay of ascorbic acid (AA) is established using a nanoprobe composed of guanine-rich single stranded DNA (G-rich ssDNA) and cobalt oxyhydroxide (CoOOH) nanosheets. It is based on competitive reduction of CoOOH by p-phenylenediamine (PPD) and AA. Thioflavine T (ThT) induces the formation of fluorescent G-quadruplex/ThT complex. The oxidized form of PPD (oxPPD) can quench the fluorescence via fluorescence resonance energy transfer (FRET), but AA suppresses quenching.