The Usefulness of X-ray Diffraction and Thermal Analysis to Study Dietary Supplements Containing Iron.

X-ray powder diffraction (XRPD) and thermal analysis (differential scanning calorimetry/derivative of thermogravimetry (DSC/DTG)) are solid-state techniques that can be successfully used to identify and quantify various chemical compounds in polycrystalline mixtures, such as dietary supplements or drugs. In this work, 31 dietary supplements available on the Polish market that contain iron compounds, namely iron gluconate, fumarate, bisglycinate, citrate and pyrophosphate, were evaluated. The aim of the work was to identify iron compounds declared by the manufacturer as food supplements and to try to verify compliance with the manufacturer's claims. Studies performed by X-ray and thermal analysis confirmed that crystalline iron compounds (iron (II) gluconate, iron (II) fumarate), declared by the manufacturers, were present in the investigated dietary supplements. Iron (II) bisglycinate proved to be semi-crystalline. However, depending on the composition of the formulation, it was possible to identify this compound in the tested supplements. For amorphous iron compounds (iron (III) citrate and iron (III) pyrophosphate), the diffraction pattern does not have characteristic diffraction lines. Food supplements containing crystalline iron compounds have a melting point close to the melting point of pure iron compounds. The presence of excipients was found to affect the shapes and positions of the endothermic peaks significantly. Widening of endothermic peaks and changes in their position were observed, as well as exothermic peaks indicating crystallization of amorphous compounds. Weight loss was determined for all dietary supplements tested. Analysis of the DTG curves showed that the thermal decomposition of most food supplements takes place in several steps. The results obtained by a combination of both simple, relatively fast and reliable XRPD and DSC/DTG methods are helpful in determining phase composition, pharmaceutical abnormalities or by detecting the presence of the correct polymorphic form.

Separation and quantification of 2-keto-3-deoxy-gluconate (KDG) a major metabolite in pectin and alginate degradation pathways.

A rapid and sensitive High Performance Liquid Chromatography (HPLC) method with photometric and fluorescence detection is developed for routine analysis of 2-Keto-3-deoxy-gluconate (KDG), a catabolite product of pectin and alginate. These polysaccharides are primary-based compounds for biofuel production and for generation of high-value-added products. HPLC is performed, after derivatization of the 2-oxo-acid groups of the metabolite with o-phenylenediamine (oPD), using a linear gradient of trifluoroacetic acid and acetonitrile. Quantification is accomplished with an internal standard method. The gradient is optimized to distinguish KDG from its close structural analogues such as 5-keto-4-deoxyuronate (DKI) and 2,5-diketo-3-deoxygluconate (DKII). The proposed method is simple, highly sensitive and accurate for time course analysis of pectin or alginate degradation.

Gluconic acid as a chelator to improve clarity of skim milk powder dispersions at pH 3.0.

Clear acidic protein beverages have a niche market. Acidification of skim milk powder (SMP) dispersions to pH 3.0 using citric acid (CA) lowers turbidity but the dispersion remains translucent. The present study aimed at comparing physicochemical properties of 5% w/v SMP dispersions acidified to pH 3.0 using chelating gluconic acid (GA) and CA and non-chelating hydrochloric acid. GA was the most effective in reducing the dispersion turbidity to 394 NTU at pH 3.0, which was further reduced to 248 NTU after heating at 90 °C for 2 min resulting in transparent dispersions. The better chelating ability of GA than CA was supported by the higher extent of dissolved CCP in serum phase. The aggregation of dissociated caseins was not observed for the GA treatment based on transmission electron microscopy. The findings from this study may be used to produce clear casein-based protein beverages.

Isotopically Enriched Tracers and Inductively Coupled Plasma Mass Spectrometry Methodologies to Study Zinc Supplementation in Single-Cells of Retinal Pigment Epithelium in Vitro.

Mass spectrometry-based techniques, such as inductively coupled plasma mass spectrometry (ICPMS) and laser ablation (LA) ICPMS, combined with an isotope pattern deconvolution mathematical tool are proposed for a better understanding of supplementation studies in cultured cells. An in vitro model of human retinal pigment epithelium (HRPEsv) cells was treated with different concentrations (0-150 µm Zn, 1 mL) of enriched stable isotope tracers of Zn in the form of sulfate and/or gluconate. Supplementations with t68ZnSO4 or t70Zn-gluconate alone and in combination (1:1 molar ratio) were investigated to evaluate the exogenous contribution and distribution of Zn in the treated cells. In order to obtain not only the Zn concentration for a cell population (mineralized cells) but also single cell information about the contribution of exogenous Zn and their distribution within micrometer cells structures, LA-ICPMS was employed to directly analyze cryopreserved cells. natZn, t68Zn, and t70Zn molar fraction images obtained from cells and cell aggregates allowed confirming the uptake of exogenous Zn by HRPEsv cells, being t68Zn and t70Zn molar fractions close to 1 in the cell nuclei. Under the selected experimental conditions tested (24 h treatments), no significant differences were obtained in the Zn distribution depending on its chemical form.

Stability Study and Identification of Degradation Products of Caffeoylgluconic Acid Derivatives from Fructus Euodiae.

Caffeoylgluconic acid derivatives are characteristic constituents isolated from the aqueous extract of Fructus Euodiae. In this research focusing on caffeoylgluconic acid derivatives, trans-caffeoyl-6-O-d-gluconic acid (CGA), trans-caffeoyl-6-O-d-gluconic acid methyl ester (CGA-ME), and trans-caffeoyl-6-O-d-glucono-γ-lactone (CGA-LT), a systematic study of stability was performed under different temperatures and pH levels by ultra performance liquid chromatography-diode array detector (UPLC-DAD) and ultra performance liquid chromatography-diode array detector/electrospray ionization-quadrupole-time of flight mass spectrometry (UPLC-DAD/ESI-Q-TOF MS). From the concentration⁻time curves and sensitivity index (SeI), it was found that compared to CGA, which is inert to the variation of temperature and pH in the tested range, CGA-ME and CGA-LT were more sensitive, with stabilities more likely to be influenced by temperature. Considering the stability index (StI), the integrated stability of CGA was the best, and that of CGA-ME was the worst. In terms of the quasi-molecular and fragment ions of the tested compounds, the degradation products were identified or tentatively characterized, which could shed light on the degradation pathways. CGA-ME and CGA-LT were easily converted to CGA by hydrolytic reaction, all of which were susceptible to the formation of isomers. This study elucidated the degradation mechanism of caffeoylgluconic acid derivatives, contributing to better guidance on manufacturing and controlling the quality of drugs.

Evaluation of aluminium mobilization from its soil mineral pools by simultaneous effect of Aspergillus strains' acidic and chelating exometabolites.

This contribution investigates aluminium mobilization from main aluminium pools in soils, phyllosilicates and oxyhydroxides, by acidic and chelating exometabolites of common soil fungi Aspergillus niger and A. clavatus. Their exometabolites' acidity as well as their ability to extract aluminium from solid mineral phases differed significantly during incubation. While both strains are able to mobilize aluminium from boehmite and aluminium oxide mixture to some extent, A. clavatus struggles to mobilize any aluminium from gibbsite. Furthermore, passive and active fungal uptake of aluminium enhances its mobilization from boehmite, especially in later growth phase, with strong linear correlation between aluminium bioaccumulated fraction and increasing culture medium pH. We also provide data on concentrations of oxalate, citrate and gluconate which are synthesized by A. niger and contribute to aluminium mobilization. Compared to boehmite-free treatment, fungus reduces oxalate production significantly in boehmite presence to restrict aluminium extraction efficiency. However, in presence of high phyllosilicates' dosages, aluminium is released to an extent that acetate and citrate is overproduced by fungus. Our results also highlight fungal capability to significantly enhance iron and silicon mobility as these elements are extracted from mineral lattice of phyllosilicates by fungal exometabolites alongside aluminium.

Production of Chemicals by Klebsiella pneumoniae Using Bamboo Hydrolysate as Feedstock.

Bamboo is an important biomass, and bamboo hydrolysate is used by Klebsiella pneumoniae as a feedstock for chemical production. Here, bamboo powder was pretreated with NaOH and washed to a neutral pH. Cellulase was added to the pretreated bamboo powder to generate the hydrolysate, which contained 30 g/L glucose and 15 g/L xylose and was used as the carbon source to prepare a medium for chemical production. When cultured in microaerobic conditions, 12.7 g/L 2,3-butanediol was produced by wildtype K. pneumoniae. In aerobic conditions, 13.0 g/L R-acetoin was produced by the budC mutant of K. pneumoniae. A mixture of 25.5 g/L 2-ketogluconic acid and 13.6 g/L xylonic acid was produced by the budA mutant of K. pneumoniae in a two-stage, pH-controlled fermentation with high air supplementation. In the first stage of fermentation, the culture was maintained at a neutral pH; after cell growth, the fermentation proceeded to the second stage, during which the culture was allowed to become acidic.

Creatine salts provide neuroprotection even after partial impairment of the creatine transporter.

Creatine, a compound that is critical for energy metabolism of nervous cells, crosses the blood-brain barrier (BBB) and the neuronal plasma membrane with difficulty, and only using its specific transporter. In the hereditary condition where the creatine transporter is defective (creatine transporter deficiency) there is no creatine in the brain, and administration of creatine is useless lacking the transporter. The disease is severe and incurable. Creatine-derived molecules that could cross BBB and plasma membrane independently of the transporter might be useful to cure this condition. Moreover, such molecules could be useful also in stroke and other brain ischemic conditions. In this paper, we investigated three creatine salts, creatine ascorbate, creatine gluconate and creatine glucose. Of these, creatine glucose was ineffective after transporter block with guanidine acetic acid (GPA) administration. Creatine ascorbate was not superior to creatine in increasing tissue creatine and phosphocreatine content after transporter impairment, however even after such impairment it delayed synaptic failure during anoxia. Finally, creatine gluconate was superior to creatine in increasing tissue content of creatine after transporter block and slowed down PS disappearance during anoxia, an effect that creatine did not have. These findings suggest that coupling creatine to molecules having a specific transporter may be a useful strategy in creatine transporter deficiency. In particular, creatine ascorbate has effects comparable to those of creatine in normal conditions, while being superior to it under conditions of missing or impaired creatine transporter.

Inhibitory effect of quercetin in the formation of advance glycation end products of human serum albumin: An in vitro and molecular interaction study.

Non-enzymatic glycation entails the reaction between the carbonyl group of a sugar with the amino group of a protein giving rise to Schiff base and Amadori products. The formation of advanced glycation end products (AGEs) leads to the generation of free radicals, which play an important role in the pathophysiology of ageing and diabetes. Bioavailable dietary antioxidants like quercetin (QC) are thought to inhibit AGEs formation. This study was aimed to investigate the effect of quercetin on AGE formation and features the glycation of human serum albumin (HSA) and its characterization by various spectroscopic techniques. The effect of quercetin, against the formation of AGEs was studied using a glycated human serum albumin product, haemoglobin-δ-gluconolactone, and aminoguanidine. The results were then corroborated with estimation of protein oxidation, lipid peroxidation and comet assay. On the basis of the experimental data, computational docking studies were then performed to understand the location of the site of quercetin binding and its best bound conformation with respect to human serum albumin. Through this study we have demonstrated the mechanism of formation of AGE and its inhibition by quercetin. We have also suggested that the supplementation with dietary antioxidants like quercetin might protect against free radical toxicity.

Casein/pectin nanocomplexes as potential oral delivery vehicles.

Delivery systems prepared with natural biopolymers are of particular interests for applications in food, pharmaceutics and biomedicine. In this study, nanocomplex particles of sodium caseinate (NaCas) and pectin were fabricated and investigated as potential oral delivery vehicles. Nanocomplexes were prepared with three mass ratios of NaCas/pectin by acidification using glucono-δ-lactone and thermal treatment. NaCas/pectin at 1:1 mass ratio resulted in dispersions with the lowest turbidity and the smallest and most uniform nanocomplexes. Thermal treatment at 85 °C for 30 min facilitated the formation of stable, compact, and spherical nanocomplexes. Heating not only greatly increased the yield of nanocomplexes but also significantly improved the encapsulation capability of rutin studied as a model compound. Pectin in nanocomplexes delayed the hydrolysis of NaCas by pepsin at gastric conditions and enabled the controlled release of most rutin in simulated intestinal conditions. The nanocomplexes based on food-sourced biopolymers have promising features for oral delivery of nutrients and medicines.

188Re-ZHER2:V2, a promising affibody-based targeting agent against HER2-expressing tumors: preclinical assessment.

UNLABELLED: Affibody molecules are small (7 kDa) nonimmunoglobulin scaffold proteins with favorable tumor-targeting properties. Studies concerning the influence of chelators on biodistribution of (99m)Tc-labeled Affibody molecules demonstrated that the variant with a C-terminal glycyl-glycyl-glycyl-cysteine peptide-based chelator (designated ZHER2:V2) has the best biodistribution profile in vivo and the lowest renal retention of radioactivity. The aim of this study was to evaluate (188)Re-ZHER2:V2 as a potential candidate for radionuclide therapy of human epidermal growth factor receptor type 2 (HER2)-expressing tumors. METHODS: ZHER2:V2 was labeled with (188)Re using a gluconate-containing kit. Targeting of HER2-overexpressing SKOV-3 ovarian carcinoma xenografts in nude mice was studied for a dosimetry assessment. RESULTS: Binding of (188)Re-ZHER2:V2 to living SKOV-3 cells was demonstrated to be specific, with an affinity of 6.4 ± 0.4 pM. The biodistribution study showed a rapid blood clearance (1.4 ± 0.1 percentage injected activity per gram [%ID/g] at 1 h after injection). The tumor uptake was 14 ± 2, 12 ± 2, 5 ± 2, and 1.8 ± 0.5 %IA/g at 1, 4, 24, and 48 h after injection, respectively. The in vivo targeting of HER2-expressing xenografts was specific. Already at 4 h after injection, tumor uptake exceeded kidney uptake (2.1 ± 0.2 %IA/g). Scintillation-camera imaging showed that tumor xenografts were the only sites with prominent accumulation of radioactivity at 4 h after injection. Based on the biokinetics, a dosimetry evaluation for humans suggests that (188)Re-ZHER2:V2 would provide an absorbed dose to tumor of 79 Gy without exceeding absorbed doses of 23 Gy to kidneys and 2 Gy to bone marrow. This indicates that future human radiotherapy studies may be feasible. CONCLUSION: (188)Re-ZHER2:V2 can deliver high absorbed doses to tumors without exceeding kidney and bone marrow toxicity limits.

Gluconic acid from biomass fast pyrolysis oils: specialty chemicals from the thermochemical conversion of biomass.

Fast pyrolysis of biomass to produce a bio-oil followed by catalytic upgrading is a widely studied approach for the potential production of fuels from biomass. Because of the complexity of the bio-oil, most upgrading strategies focus on removing oxygen from the entire mixture to produce fuels. Here we report a novel method for the production of the specialty chemical, gluconic acid, from the pyrolysis of biomass. Through a combination of sequential condensation of pyrolysis vapors and water extraction, a solution rich in levoglucosan is obtained that accounts for over 30% of the carbon in the bio-oil produced from red oak. A simple filtration step yields a stream of high-purity levoglucosan. This stream of levoglucosan is then hydrolyzed and partially oxidized to yield gluconic acid with high purity and selectivity. This combination of cost-effective pyrolysis coupled with simple separation and upgrading could enable a variety of new product markets for chemicals from biomass.

[The use of semi-synthetic polymers in the formulation of sucking and chewable tablets containing sage extract and zinc gluconate]. / Zastosowanie pólsyntetycznych polimerów w formulacji tabletek do ssania i zucia zawierajacych ekstrakt z szalwii i glukonian cynku.

BACKGROUND: Halitosis and gingivitis are most common pathologies (15-60% of population) which, if left untreated, lead to periodontal diseases and tooth loss. OBJECTIVES: The aim of this study was to develop, based on polymers of dry sage extract and zinc gluconate, tablets intended for sucking and chewing that can be applied in the treatment of halitosis and gingivitis. MATERIAL AND METHODS: Dried aqueous sage extract, zinc gluconate, Pharmagum M, Prosolv SMCC90 and SMCCHD90, Vivapur 102, sorbitol, mannitol, ludipress. Direct tableting. Testing pharmacopeial parameters and pharmaceutical availability (using basket and rotating disk methods) of tablets intended for sucking and chewing. Approximation of the obtained results. RESULTS: Grey and green color tablets were obtained with smooth and uniform surface, without stains, spalls or mechanical damage. The determined average mass (weight) of a tablet complied with the standard. The friability and crushing strength test revealed that tablets containing Prosolv SMCCHD90, Vivapur 102 and mannitol demonstrated the highest mechanical strength. Tablets containing these substances and intended for sucking had prolonged disintegration and release time. Tablets intended for chewing had a hardness at the level of 124 N.They demonstrated compressibility, low friability and prolonged release. The release profiles of tablets intended for sucking (v2) and those for chewing, obtained by basket and rotating disk methods, were similar. CONCLUSIONS: The addition of Prosolv SMCCHD90, Vivapur 102 and mannitol increased significantly the mechanical strength (higher hardness, lower friability), prolonged the disintegration time and slowed the release from the obtained tablets intended for sucking and chewing. The application of Prosolv SMCCHD90 in the formulation of tablets for chewing carries the risk for sorption of active components to the polymer structure. This process takes place in the early stage of the release. Rotating disk method used in pharmaceutical availability testing gives better results while analyzing the phenomenon than the standard basket method. The suggested and tested formulations of tablets intended for sucking and chewing may be used as an alternative to formulations containing dried titrated extracts from plants of antimicrobial activity (sage - Salvia officinalis) in combination with substances binding volatile sulfur compounds (zinc gluconate).

Effects of sucrose and urea on soy hull pectic polysaccharide gel induced by D-glucono-1,5-lactone.

Gelation properties of pectic polysaccharide extracted with ammonium oxalate from soybean hulls assisted by microwave were seldom studied. Water mobility in soy hull pectic polysaccharide (SHPP) was firstly studied by low field NMR. D-Glucono-1,5-lactone (GDL) and sucrose both could decrease spin-spin relaxation times (T2) of SHPP solutions which indicated the SHPP network formed. Rheological analysis conformed that SHPP gel was formed induced by GDL and enhanced by sucrose. Urea can increase T2 and collapse the network of SHPP. TGA was used to draw the profiles of water desorption from SHPP solutions or gels, during heating at a controlled rate. It was found that sucrose increased the bound water content and urea acted a conversely role. Hydrogen bond is the main force to maintain SHPP gel network.

Purification and physicokinetic characterization of a gluconolactone inhibition-insensitive ß-glucosidase from Andrographis paniculata nees. Leaf.

A gluconolactone inhibition-insensitive ß-glucosidase from Andrographis paniculata (Acanthaceae) leaves has been isolated, homogeneity purified, and characterized for its physicokinetic properties. The purified enzyme appeared to be a monomeric structure with native molecular weight about 60 kD. The enzyme exhibited optimum pH 5.5 and pI 4.0, meso-thermostability and high temperature optimum (55°C) for catalytic activity, with activation energy of 6.8 kcal Mol(-1). The substrate saturation kinetics studies of the enzyme revealed a Michaelis-Menten constant (Km) of 0.25 mM for pNPG and catalytic efficiency (Kcat/Km) of 52,400 M (-1) s(-1), respectively. Substrate specificity of the enzyme was restricted to ß-linked gluco-, manno- and fuco-conjugates. The gluconolactone inhibition insensitivity was evident from its very low inhibition at millimolar inhibitor concentrations. Interestingly, the enzyme showed geraniol transglucosylating activity with pNPG as glucosyl donor but not with cellobiose. The catalytic activity of the enzyme has been reported to be novel with respect to its activity and preferences from a medicinal plant resource.

[Preparation of multi-hydroxyl molecular-bonded stationary phase for hydrophilic interaction chromatography and its separation property].

The surface of silica was modified by delta-gluconolactone, a multi-hydroxyl molecule, to prepare a new stationary phase for hydrophilic interaction chromatography (HILIC) of strongly polar compounds from traditional Chinese medicine. The separation properties and separation mechanisms of the stationary phase to six polar components were investigated by changing kinds of organic solvent (ethanol, acetonitrile and tetrahydrofuran) and concentration, salt concentration and column temperature. The retention times of the solutes decrease with increasing the concentration of water in mobile phase from 0 to 40% (v/v), indicating a typical HILIC mode for the separation of the solutes, whilst the curves of the retention times of the six solutes exhibit "U" shape with the change in the concentration of the water from 0 to 100% (v/v), indicating a mixed-mode of hydrophilic interaction and reversed-phase chromatography working on the separation of the solutes. The results of the salt concentration and pH affected the retention time show that there were weak electric interactions between the solutes and the prepared stationary phase. The fact that the strongly polar solutes and Danshen injections could be separated well indicated that the prepared stationary phase has a potential application in the separation of strongly polar components in traditional Chinese medicine and other strongly polar compounds.

Complexation of bovine serum albumin and sugar beet pectin: structural transitions and phase diagram.

The complexation between bovine serum albumin (BSA) and sugar beet pectin (SBP) was studied in situ by coupling glucono-δ-lactone (GDL) induced acidification with dynamic light scattering and turbidity measurements. Individual measurements at specific pHs and mixing ratios were also carried out using zeta potentiometry, gel permeation chromatography-multiangle laser light scattering (GPC-MALLS), and isothermal titration calorimetry (ITC). These investigations together enabled the establishment of a phase diagram of BSA/SBP and the identification of the molecular events during protein/polysaccharide complexation in relation to the phase diagram, which showed five regions: (I) a stable region of mixed individual soluble polymers, (II) a stable region of intramolecular soluble complexes, (III) a quasi-stable region of intermolecular soluble complexes, (IV) an unstable region of intermolecular insoluble complexes, and (V) a second stable region of mixed individual soluble polymers, on lowering pH. We found for the first time that the complexation could take place well above the critical pH(c), the value that most previous studies had regarded as the onset occurrence of complexation. A model of structural transitions between the regions was proposed. The borderline between region II and region III represents the BSA/SBP stoichiometry for intramolecular soluble complex at a specific pH, while that between region III and region IV identifies the composition of the intermolecular insoluble complex. Also studied was the effect of NaCl and CaCl(2) on the phase diagram and structural transitions.

Ellagic acid, a new antiglycating agent: its inhibition of Nϵ-(carboxymethyl)lysine.

Non-enzymatic glycation is a complex series of reactions between reducing sugars and amino groups of proteins. Accumulation of AGEs (advanced glycation end-products) due to non-enzymatic glycation has been related to several diseases associated with aging and diabetes. The formation of AGEs is accelerated in hyperglycaemic conditions, which alters the structure and function of long-lived proteins, thereby contributing to long-term diabetic complications. The present study describes AGE inhibition and the mechanism of action of a new antiglycating agent, EA (ellagic acid), a flavonoid present in many dietary sources. Inhibition of AGE formation by EA was demonstrated with different proteins, namely eye lens TSP (total soluble protein), Hb (haemoglobin), lysozyme and BSA, using different glycating agents such as fructose, ribose and methylglyoxal by a set of complementary methods. These results suggest that the antiglycating action of EA seems to involve, apart from inhibition of a few fluorescent AGEs, predominantly inhibition of CEL [Nϵ-(carboxyethyl)lysine] through scavenging of the dicarbonyl compounds. Furthermore, MALDI-TOF-MS (matrix-assisted laser-desorption ionisation-time-of-flight MS) analysis confirms inhibition of the formation of CEL on lysozyme on in vitro glycation by EA. Prevention of glycation-mediated ß-sheet formation in Hb and lysozyme by EA confirm its antiglycating ability. Inhibition of glycosylated Hb formation in human blood under ex vivo high-glucose conditions signifies the physiological antiglycating potential of EA. We have also determined the effectiveness of EA against loss of eye lens transparency through inhibition of AGEs in the lens organ culture system. These findings establish the antiglycating potential of EA and its in vivo utility in controlling AGE-mediated diabetic pathologies.

Acidulant and oven type affect total anthocyanin content of blue corn cookies.

BACKGROUND: Anthocyanins, pink to purple water-soluble flavonoids, are naturally occurring pigments with claimed health benefits. However, they are sensitive to degradation by high pH, light and temperature. Blue corn (maize) contains high levels of anthocyanins. Cookies are popular snacks and might serve as a vehicle to deliver antioxidants. A cookie formula with a high level of blue corn was developed with added acidulents and baked in ovens with different heat transfer coefficients. RESULTS: The best whole-grain blue corn flour/wheat pastry flour ratio (80:20 w/w), guar gum level (10 g kg(-1), flour weight basis) and water level (215 g kg(-1), flour weight basis) were determined based on response surface methodology analysis. The interactions of citric and lactic acids and glucono-δ-lactone with three oven types having different heat transfer coefficients (impingement oven 179 °C/4 min, reel oven 204 °C/10 min and convection oven 182 °C/4 min) influenced the total anthocyanin content (TAC) remaining in blue corn-containing cookies after baking. CONCLUSION: Cookies baked with citric acid in the convection oven retained the maximum TAC (227 ± 3 mg kg(-1)). By baking rapidly at lower temperatures and adding acidulents, it may be possible to increase residual natural source antioxidants in baked foods.

Crystallization and preliminary X-ray analysis of 5-keto-D-gluconate reductase from Gluconobacter suboxydans IFO12528 complexed with 5-keto-D-gluconate and NADPH.

NADPH-dependent 5-keto-D-gluconate reductase from Gluconobacter suboxydans IFO12528 (5KGR) catalyzes oxidoreduction between 5-keto-D-gluconate and D-gluconate with high specificity. 5KGR was expressed in Escherichia coli, purified and crystallized with 5-keto-D-gluconate and NADPH using the sitting-drop vapour-diffusion method at 288 K. A crystal of the 5KGR-NADPH complex was obtained using reservoir solution containing PEG 4000 as a precipitant and diffracted X-rays to 1.75 Šresolution. The crystal of the complex belonged to space group P4(2)2(1)2, with unit-cell parameters a=b=128.6, c=62.9 Å. A crystal of the 5KGR-NADPH-5-keto-D-gluconate complex was prepared by soaking the 5KGR-NADPH complex crystal in reservoir solution supplemented with 100 mM 5-keto-D-gluconate and 10 mM NADPH for 20 min and diffracted X-rays to 2.26 Šresolution. The crystal of the ternary complex belonged to space group P4(2)2(1)2, with unit-cell parameters a=b=128.7, c=62.5 Å. Both crystals contained two molecules in the asymmetric unit.