Sensitive spectrophotometric determination of ascorbic acid in fruit juices and pharmaceutical formulations using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP)

A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP). The iron(II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 × 10⁵ l mole^–1cm^–1 and 5.69 × 10⁴ l mole^–1cm^–1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 μg ml^–1, a calibration sensitivity of 0.744 ml μg^–1 at 560 nm and 0.323 ml μg^–1 at 748 nm, and a detection limit of 15 ng ml^–1 and 44 ng ml^–1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations. The results demonstrated a good precision (R.S.D. < 1%) and are in agreement with those obtained with others methods. The Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system. Received: 7 May 1996 / Revised: 1 July 1996 / Accepted: 8 August 1996     

Chemical Composition and Antioxidant Activity of Essential Oils from Eugenia patrisii Vahl,E. punicifolia (Kunth) DC., and Myrcia tomentosa (Aubl.) DC., Leaf of Family Myrtaceae

Essential oils (EOs) were extracted from Eugenia patrisii, E. punicifolia, and Myrcia tomentosa, specimens A and B, using hydrodistillation. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the volatile constituents present, and the antioxidant capacity of EOs was determined using diphenylpicryl-hydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. For E. patrisii, germacrene D (20.03%), bicyclogermacrene (11.82%), and (E)-caryophyllene (11.04%) were identified as the major constituents of the EOs extracted from specimen A, whereas specimen B primarily comprised γ-elemene (25.89%), germacrene B (8.11%), and (E)-caryophyllene (10.76%). The EOs of E. punicifolia specimen A contained β-Elemene (25.12%), (E)-caryophyllene (13.11%), and bicyclogermacrene (9.88%), while specimen B was composed of (E)-caryophyllene (11.47%), bicyclogermacrene (5.86%), β-pinene (5.86%), and γ-muurolene (5.55%). The specimen A of M. tomentosa was characterized by γ-elemene (12.52%), germacrene D (11.45%), and (E)-caryophyllene (10.22%), while specimen B contained spathulenol (40.70%), α-zingiberene (9.58%), and γ-elemene (6.89%). Additionally, the chemical composition of the EOs was qualitatively and quantitatively affected by the collection period. Furthermore, the EOs of the studied specimens, especially specimen A of E. punicifolia, showed a greater antioxidant activity in DPPH rather than TEAC, as represented by a significantly high inhibition percentage (408.0%).     

Capillary electrophoresis method for analysis of inorganic and organic anions related to habitability and the search for life

In situ missions of exploration require analytical methods that are capable of detecting a wide range of molecular targets in complex matrices without a priori assumptions of sample composition. Furthermore, these methods should minimize the number of reagents needed and any sample preparation steps. We have developed a method for the detection of metabolically relevant inorganic and organic anions that is suitable for implementation on in situ spaceflight missions. Using 55 mM acetic acid, 50 mM triethylamine, and 5% glycerol, more than 21 relevant anions are separated in less than 20 min. The method is robust to sample ionic strength, tolerating high concentrations of background salts (up to 900 mM NaCl and 300 mM MgSO₄). This is an important feature for future missions to ocean worlds. The method was validated using a culture of Escherichia coli and with high salinity natural samples collected from Mono Lake, California.     

Hybrid EuIII Coordination Luminophore Standing on Two Legs on Silica Nanoparticles for Enhanced Luminescence

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent Ln^III-silica nanomaterials. A novel Eu^III-silica hybrid nanoparticle was developed by using a doubly binding TPPO−Si(OEt)₃ (TPPO: triphenyl phosphine oxide) linker. The TPPO−Si(OEt)₃ was confirmed by ¹H, ³¹P, ²⁹Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)₃ and Eu(tfc)₃ moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO−Si(OEt)₃-modified silica nanoparticles, producing Eu(hfa)₃(TPPO−Si)₂-SiO₂ and Eu(tfc)₃(TPPO−Si)₂-SiO₂, respectively. Eu(hfa)₃(TPPO−Si)₂−SiO₂ exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported Eu^III-based hybrid materials. Eu(tfc)₃(TPPO−Si)₂−SiO₂ showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)₃(TPPO−Si(OEt)₃)₂ was found to be 39 %. These results confirmed that the TPPO−Si(OEt)₃ linker is a promising candidate for development of Eu^III-based luminescent materials.     

The glucocorticoid derivative with the phthalimide group cationic nanocrystal for ophthalmic application: a design space development approach

The glucocorticoid derivative of budesonide with a phthalimide group is a drug candidate to treat inflammatory eye diseases; nevertheless, it presents low water solubility. Drug nanocrystals have been proposed to overcome this hurdle. The development of an innovative ophthalmic anti-inflammatory nanosuspension was performed using a design space approach. We obtained the particle size reduction of this glucocorticoid derivative on a nanometer scale (approximately 165.0 nm), applying wet bead milling on a super reduced scale. The design of experiment supported the optimization of the formula evaluating the parameters that influence reducing the particle size and also allowed determining the design space. Considering the two statistical models developed and the size range obtained, we proposed that the optimized formulation for the glucocorticoid derivative nanosuspension may be 1.0 wt% glucocorticoid derivative and 0.092 wt% cetylpyridinium chloride. This formulation was characterized by the morphological, physical–chemical, and mucoadhesive in vitro test and showed potential for ophthalmic use with reduced frequency of product application, improved efficiency, and safety, which may promote better patient compliance.     

Structural and electronic properties of amorphous bismuth calcium borate from first-principle calculations

Structural Chemistry - We investigatethe electronic and structural properties of two new amorphous materials, Bi6Ca2O28B12 and Bi6Ca2 O28B11:Tm, using density functional theory with a short-range...     

Chemical Composition of Volatile Compounds in Apis mellifera Propolis from the Northeast Region of Pará State,Brazil

Propolis is a balsamic product obtained from vegetable resins by exotic Africanized bees Apis mellifera L., transported and processed by them, originating from the activity that explores and maintains these individuals. Because of its vegetable and natural origins, propolis is a complex mixture of different compound classes; among them are the volatile compounds present in the aroma. In this sense, in the present study we evaluated the volatile fraction of propolis present in the aroma obtained by distillation and simultaneous extraction, and its chemical composition was determined using coupled gas chromatography, mass spectrometry, and flame ionization detection. The majority of compounds were sesquiterpene and hydrocarbons, comprising 8.2–22.19% α-copaene and 6.2–21.7% β-caryophyllene, with additional compounds identified in greater concentrations. Multivariate analysis showed that samples collected from one region may have different chemical compositions, which may be related to the location of the resin’s production. This may be related to other bee products.     

Detection of Frozen–Thawed Duck Fatty Liver by MALDI-TOF Mass Spectrometry: A Chemometrics Study

The marketing of poultry livers is only authorized as fresh, frozen, or deep-frozen. The higher consumer demand for these products for a short period of time may lead to the marketing of frozen–thawed poultry livers: this constitutes fraud. The aim of this study was to design a method for distinguishing frozen–thawed livers from fresh livers. For this, the spectral fingerprint of liver proteins was acquired using Matrix-Assisted Laser Dissociation Ionization-Time-Of-Flight mass spectrometry. The spectra were analyzed using the chemometrics approach. First, principal component analysis studied the expected variability of commercial conditions before and after freezing–thawing. Then, the discriminant power of spectral fingerprint of liver proteins was assessed using supervised model generation. The combined approach of mass spectrometry and chemometrics successfully described the evolution of protein profile during storage time, before and after freezing-thawing, and successfully discriminated the fresh and frozen–thawed livers. These results are promising in terms of fraud detection, providing an opportunity for implementation of a reference method for agencies to fight fraud.     

Design and Functionalization of a µPAD for the Enzymatic Determination of Nitrate in Urine

In this work, the design of a microfluidic paper-based analytical device (μPAD) for the quantification of nitrate in urine samples was described. Nitrate monitoring is highly relevant due to its association to some diseases and health conditions. The nitrate determination was achieved by combining the selectivity of the nitrate reductase enzymatic reaction with the colorimetric detection of nitrite by the well-known Griess reagent. For the optimization of the nitrate determination μPAD, several variables associated with the design and construction of the device were studied. Furthermore, the interference of the urine matrix was evaluated, and stability studies were performed, under different conditions. The developed μPAD enabled us to obtain a limit of detection of 0.04 mM, a limit of quantification of 0.14 mM and a dynamic concentration range of 0.14–1.0 mM. The designed μPAD proved to be stable for 24 h when stored at room temperature in air or vacuum atmosphere, and 60 days when stored in vacuum at −20 °C. The accuracy of the nitrate μPAD measurements was confirmed by analyzing four certified samples (prepared in synthetic urine) and performing recovery studies using urine samples.     

Chemical Physical Characterization and Profile of Fruit Volatile Compounds from Different Accesses of Myrciaria floribunda (H. West Ex Wild.) O. Berg through Polyacrylate Fiber

Among the many species of native fruit of Brazil that have been little explored, there is Myrciaria floribunda (also known as rumberry, cambuizeiro, or guavaberry), a species with significant variability, which has fruits of different colors (orange, red, and purple) when ripe. The physical-chemical characteristics evaluated were fruit weight (FW), seed weight (SW), pulp weight (PW), number of seeds (NS), longitudinal diameter (LD), transverse diameter (TD), format (LD/TD), hydrogen potential (pH), soluble solids (SS), titratable acidity (TA), and ratio (SS/TA); further, the volatile organic compounds (VOCs) of nine accesses of rumberry orchards were identified. The averages of the variables FW, SW, PW, NS, LD, TD, shape, and firmness were 0.76 g, 0.22 g, 0.54 g, 1.45, 10.06 mm, 9.90 mm, 1.02, 2.96 N, respectively. LD/TD data showed that the fruits have a slightly rounded shape (LD/TD = 1). The averages for pH, SS, TA, and SS/TA were 3.74, 17.58 Brix, 4.31% citric acid, and 4.31, respectively. The evaluated parameters indicated that the fruits can be consumed both in natura and industrialized, with the red-colored fruits presenting a good balance of SS/TA, standards demanded by the processing industries. Thirty-six VOCs were identified, with emphasis on the sesquiterpenes. Caryophyllene (21.6% to 49.3%) and γ-selinene (11.3% to 16.3%) were the most predominant compounds in rumberry fruits.