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Graphical abstract, Highlights • 25H-NBOMe and 25H-NBOH recreational drugs induces abnormal formation in zebrafish embryos. • Biophysical and theoretical studies indicate that these drugs have affinity for the DNA major groove. • The toxicity observed in the zebrafish embryos and DNA interaction may be correlated., Toxicological effects of 25H-NBOMe and 25H-NBOH recreational drugs on zebrafish embryos and larvae at the end of 96 h exposure period were demonstrated. 25H-NBOH and 25H-NBOMe caused high embryo mortality at 80 and 100 µg mL−1, respectively. According to the decrease in the concentration tested, lethality decreased while non-lethal effects were predominant up to 10 and 50 µg mL−1 of 25H-NBOH and 25H-NBOMe, respectively, including spine malformation, egg hatching delay, body malformation, otolith malformation, pericardial edema, and blood clotting. We can disclose that these drugs have an affinity for DNA in vitro using biophysical spectroscopic assays and molecular modeling methods. The experiments demonstrated that 25H-NBOH and 25H-NBOMe bind to the unclassical major groove of ctDNA with a binding constant of 27.00 × 104 M−1 and 5.27 × 104 M−1, respectively. Furthermore, these interactions lead to conformational changes in the DNA structure. Therefore, the results observed in the zebrafish embryos and DNA may be correlated.

A simple and fast method was developed for the determination of thimerosal (TH) in vaccines based on decomposition through the action of oxidizing systems of the organic mercury compound to inorganic mercury (Hgino) using cold vapor atomic fluorescence spectrometry (CVAFS) for detection. The oxidative decomposition of TH to Hgino was evaluated in four oxidizing systems: (1) KBr/KBrO3; (2) KMnO4; (3) KI/KIO3; and (4) Na2S/KMnO4 employing diluted mineral acids. Only the systems (1) and (2) presented quantitative oxidation to Hgino. The method presented high sensitivity under optimized conditions with a LOD of 0.02 μg L−1 and proved to be accurate with an RSD of ≤4.59%. The absence of a matrix effect was proven from the recovery tests applied to the vaccine samples, fortified with TH, obtaining recoveries of 80.1 to 106% (system 1) and 92.5 to 101% (system 2). Finally, the method was applied to five vaccine samples with differing TH concentrations, and the results were in agreement with a microwave-assisted digestion methodology (reference method), thus indicating the accuracy of the proposed method.

Experimental, biophysical, and molecular modelling studies between 25I-NBOH and 25I-NBOMe with human serum albumin (HSA) have indicated that these recreational drugs simultaneously bind to site I and II of the protein, with 25I-NBOMe showing a greater affinity for the transport protein, and that both compounds were able to perturb the native structure of HSA. The 25I-NBOH and 25I-NBOMe drugs spontaneously interact with protein (ΔG < 0), and with the complex formation in the ground state (static quenching). Preferred forces in the interaction process were determined as hydrogen bonding and van der Waals forces. From 1H NMR studies, it was possible to determine the epitope of the molecules, as these and other results agree with the theoretical molecular docking. Overall, our results suggest that the interaction between 25I-NBOH and 25I-NBOMe with HSA can affect its distribution in the body and cause harmful effects, resulting from conformational changes in the protein which can affect its function from the decreased availability of HSA to carry other essential compounds.

Thimerosal (TH), an organomercurial compound, is used as a preservative in vaccines and cosmetics. Its interaction with human hemoglobin (Hb) was investigated under physiological conditions using biophysical and biological assays, aiming to evaluate hazardous effects. TH interacts spontaneously with Hb (stoichiometry 2:1, ligand-protein), preferably by electrostatic forces, with a binding constant of 1.41 × 106 M−1. Spectroscopic data allows to proposing that TH induces structural changes in Hg, through ethylmercury transfer to human Hb-Cys93 residues, forming thiosalicylic acid, which, in turn, interacts with the positive side of the amino acid in the Hb-HgEt adduct chain. As a consequence, inhibition of Hb-O2 binding capacity up to 72% (human Hb), and 50% (human erythrocytes), was verified. Dose-dependent induction of TH forming advanced glycation end products (AGE) and protein aggregates (amyloids) was additionally observed. Finally, these results highlight the toxic potential of the use of TH in biological systems, with a consequent risk to human health.

Two different gold-silica-based nanomaterials were prepared: (i) silica-supported gold nanoparticles (AuNP/SiO2); and (ii) gold-silica core-shell nanoparticles (AuNP@SiO2). Three strategies for sample treatment (S), consisting in acid treatments, were employed: (S1) HNO3; (S2) HNO3 + HCl; and (S3) HF + HNO3 + HCl, applying microwave oven digestion for S2 and S3. From three calibration curves, slope, intercept, and linear correlation coefficient were obtained. The accuracy of the methods was evaluated by comparing the gold contents in a sample determined by flame atomic absorption spectrometry (FAAS) and by inductively coupled plasma atomic emission spectrometry (ICP-OES). Finally, the amount of gold for all samples was determined by FAAS. UV-Vis spectroscopy and transmission electron microscopy (TEM) were used to compare the material before and after sample treatment. By comparison, the application of S2 and S3 allowed the presence of gold on or in the silica matrix to be determined and the amount quantified.

Purpose: Quercetin is a flavonoid known for its therapeutic properties and for forming complexes. Although the antimony-quercetin (SbQ) complex has been produced before, no previous exploration of its characteristics has been published in literature. Thus, this study aimed to characterize this complex, assess its stability and investigate its complexation site through its antibacterial activity. Methods: The SbQ complex was synthetized using Sb(III) potassium tartrate trihydrate and quercetin anhydrous (1:1) (v/v) as a solution and dried using three methods: rotaevaporation, lyophilization and spray drying. The material, in solution, was analyzed by UV-vis and fluorimetry; and, in the powder, by X-ray diffraction (XRD), both scanning electronic and fluorescence microscopy and infrared spectroscopy (FT-IR). Antimicrobial activity was evaluated via broth microdilution. Results: UV-vis exhibited a shoulder peak at 291 nm indicating metal chelation at C-ring of quercetin and confirmed 1:1 stoichiometry. Spectrofluorimetry showed an increase of intensity with the complex formation with an emission band (525 nm). After drying, XRD and SEM indicated loss of crystallinity and a difference in shape and size of the complex compared to its precursors. FT-IR suggested by a shift of frequency of the carbonyl group (1661 cm-1) that the quercetin bond to antimony by the C-3, followed by positions C-5 and C-4 carbonyl, which has been confirmed by MIC through the structure-activity relationship of the antibacterial activity of quercetin. Conclusion: These results provided a characterization of SbQ complex with the confirmation of its binding site, working as a guide for future studies involving this complex.

This work aimed to evaluate the inhibition of Candida rugosa lipase by five guanylhydrazone derivatives through biological, biophysical and theoretical studies simulating physiologic conditions. The compound LQM11 (IC50 = 14.70 μM) presented the highest inhibition against the enzyme. Therefore, for a better understanding of the interaction process, spectroscopic and theoretical studies were performed. Fluorescence and UV–vis assays indicate a static quenching mechanism with non-fluorescent supramolecular complex formation and changing the native protein structure. The binding process was spontaneous (ΔG 0) played a preferential role in stabilizing the complex ligand-lipase. The compounds were classified as non-competitive inhibitors using orlistat as a reference in competition studies. Based on the 1H NMR assays it was possible to propose the sites of ligand (epitope) that bind preferentially to the enzyme and the theoretical studies were consistent with the experimental results. Finally, LQM11 was efficient as a lipase inhibitor of the crude intestinal extract of larvae of Rhynchophorus palmarum, an important agricultural plague, showing potential for control of this pest. Within this context, the real potential of this biotechnological application deserves further studies.

Twenty-six Biginelli adducts were synthesized through an ionic liquid-assisted synthesis with up to 92% yield. Sixteen of these Biginelli adducts were then assayed to determine their antiureolytic activity against purified urease from jack beans. The substances BA7-S, BA9-S and BA11-S were shown to be as efficient inhibitors as hydroxyurea, a positive control used in in vitro screening assay against urease. Fluorescence studies revealed that BA7-S, BA9-S, BA11-S and BA5-S possessed high binding constant values of 5.95, 6.72, 4.55, and 4.28 M−1, respectively, while BAS12-S, without substituents, showed a low value of log Kb = 2.16 M−1. In addition, in the most thermodynamically favorable BA5-S and BA7-S urease complexes, the corresponding Biginelli adducts were capable of interacting with the active site of urease through non-ionic interactions, such as hydrophobic interactions, or hydrogen and van der Waals interactions, respectively. In silico studies also supported that the BAs interact with the active site, confirming the fluorescence and kinetic assay studies, which clearly indicate that BA5-S and BA7-S are competitive inhibitors (Ki = 0.96 and 0.57 mM, respectively). In silico studies also showed that the substituents in the aromatic ring interact with Ni atoms to form a stable complex.

Acridines are considered an important class of compounds due to their wide variety of biological activities. In this work, we synthesized four acridine derivatives (1–4) and evaluated their biological activity against the Plasmodium falciparum W2 line, as well as studied the interaction with ctDNA and HSA using spectroscopic techniques and molecular docking. The acridine derivative 2 (IC50 = 0.90 ± 0.08 μM) was more effective against P. falciparum than primaquine (IC50 = 1.70 ± 0.10 μM) and similar to amsacrine (IC50 = 0.80 ± 0.10 μM). In the fluorescence and UV–vis assays, it was verified that the acridine derivatives interact with ctDNA and HSA leading to a non-fluorescent supramolecular complex formation. The non-covalent binding constants ranged from 2.09 to 7.76 × 103 M−1, indicating moderate interaction with ctDNA. Through experiments with KI, fluorescence contact energy transfer and competition assays were possible to characterize the main non-covalent binding mode of the acridines evaluated with ctDNA as intercalation. The binding constants obtained showed a high linear correlation with the IC50 values against the antimalarial activity, suggesting that DNA may be the main biological target of these molecules. Finally, HSA interaction studies were performed and all evaluated compounds bind to the site II of the protein. The less active compounds (1 and 3) presented the highest affinity to HSA, indicating that the interaction with carrier protein can affect the (bio)availability of these compounds to the biological target.

CdTe quantum dots (QD-CdTe) functionalized with mercaptosuccinic acid (MSA) were synthesized in an aqueous medium, varying synthesis time from 0.5 to 4 h. The nanoprobe were characterized by a direct relationship between synthesis time and QD size (2.61-3.04 nm). The QD-CdTe-MSA interacted with protamine (PT), a cationic protein, forming a bioconjugate, thus quenching the photoluminescence intensity and generating an on-off system. The nanoprobe produced at a synthesis time of 1 h (QD-CdTe1) presented PT’s best sensitivity in a succinate buffer (pH = 5). Under the optimized conditions, the proposed method presented a linear range of 0.05-0.5 mg L-1 (10-100 nM), limit of detection (LOD) 0.01 mg L-1 (2 nM), and relative standard deviation (RSD) ≤ 2.01% (n = 10). The interaction of the nanoprobe and PT led to aggregation due to a bioconjugate formation. The systems’ hydrodynamic radius varied from 4.31 nm (QD‑CdTe1) to 30.50 nm for the bioconjugate (QD-CdTe1-PT). The method was sensitive to variation in ionic strength and based on thermodynamic parameters; it was demonstrated that the interaction mechanism occurred preferentially through electrostatic forces. Finally, the method proved to be fast, sensitive, and viable for quantifying PT in drugs and synthetic urine samples with recoveries above 95%.

Urease is an enzyme associated with the degradation of urea, an important nitrogen fertilizer in agriculture. Thus, this current report describes the use of a paper-based analytical device (UrePAD) designed to contain a microzone array for colorimetric determination of urease activity in soils in the absence/presence of potential enzyme inhibitors. The UrePAD can be used at the point-of-need (point-of-care), and it offers advantages such as low cost, simplicity in handling, low sample/reagent volumes, and no use of toxic reagents. The acid-base indicator phenol red was used to monitor the urea hydrolysis reaction catalyzed by urease in the evaluated systems. The images were digitalized in a bench scanner, and the analysis was performed using Corel Draw X8 software. The device offered a LOD of 0.10 U mL−1 with linearity between 0.25 and 4.0 U mL−1 and a relative standard deviation ≤ 1.38%. UrePAD was tested in four soil samples of different characteristics and with eight urease inhibitors of varied classes. The results obtained through the proposed device did not differ statistically (95% confidence interval) from those employing the classic method based on the Berthelot reaction, thus indicating that UrePAD was effective for determining urease activity and screening inhibitors, besides showing the capacity to simplify fieldwork involving the application of urea in the soil.

The oil spill off the coast of the Brazilian Northeast region is one of the most significant global events regarding contamination and environmental impact in recent years. This work evaluates the effects of oil spills on the Northeast coasts between Alagoas and Sergipe states from October 2019 to January 2020. Analysis of some sampling points of seawater revealed the presence of Hg, Cd, Pb, and Cu in levels above the maximum concentration limits established by the Brazilian legislation. For water quality parameters, phosphorus, nitrite, and turbidity showed statistically different values. However, the chromatographic profiles of oil obtained from different beaches were quite similar. Seawater, fishes, and massunins (bivalve) presented the main polycyclic aromatic hydrocarbons: naphthalene, phenanthrene, fluoranthene, fluorene, and acenaphthalene. Therefore, the concentration of organic and inorganic contaminants determined in different environmental locations served as a subsidy to assess the effect of the preliminary oil spill on the Brazilian coast.

CdTe quantum dots (CdTe QD) have been produced at different times of synthesis (1, 2, and 4 h) using thiols as capping agents: mercaptopropionic acid (MPA), mercaptosuccinic acid (MSA) and N-acetyl- l -cysteine (NAC) using water as a solvent. The produced CdTe QD were characterized by UV–vis and photoluminescence (PL) spectroscopy and showed a relationship among reflux time, size, and spectroscopic properties. CdTe QD were shown to interact with thimerosal (TM), an organic mercury compound, and the PL intensity was effectively quenched, characterizing an ON-OFF process. However, the NAC capped CdTe (CdTe-NAC) at 1 h presented the best sensitivity for TM determination. Under optimized conditions, a linear range from 0.1 to 1.0 μg mL−1 (0.25–2.5 μM) and a LOD of 26.6 μg L−1 (66.7 nM) were achieved. The influence of different mercuric species [Hg(II), methylmercury, ethylmercury, and phenylmercury], along with thiosalicylic acid (TSA), and other ionic species on the sensitivity of the method and the interaction mechanism between TM and CdTe-NAC have been discussed. The method was successfully applied for direct quantification of TM in vaccines, and the results were validated by cold vapor atomic fluorescence spectroscopy (CV AFS). Finally, the proposed method proved to be fast, sensitive, and simple for suitable use in vaccine quality control.

This work proposes a spectrofluorometric method for the determination of total antioxidant capacity (CAO) in beverage samples, based on inhibition of thiochrome formation (λex = 370 nm, λem = 440 nm); a product of thiamine (vitamin B1) oxidation from K3Fe(CN)6. In the development of the method, gallic acid (GA) was used as a reference, and inhibition of thiochrome formation (in percentage) was used as the analytical response. The selectivity of the method was evaluated using seven different compounds (gallic acid, ascorbic acid, quercetin, butylhydroxytoluene (BHT), 6-hydroxy-2,5,7,8-tetramethylchroman-2 (Trolox), cysteine, and glucose). As proof of concept, the proposed method was applied in the determination of CAO in different samples, such as teas and infusions, red wines, and white wines. The results were compared with the Folin-Ciocalteu (FC), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS•+), and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) methods using the linear correlation between the methods (at 95% confidence). We observed excellent agreement between the proposed method and FC (correlation coefficient (r) = 0.9768) and ABTS•+ (r = 0.9842), compared with DPPH• method (r = 0.8502). For the determination of total CAO in beverages, the proposed method developed proved to be fast, sensitive, simple, and the results were in agreement with established assays.

The importance of evaluating how natural organic matter influences the mobility of arsenic species in an ecosystem is an environmental concern. This work aimed to evaluate the interaction between humic substances (HS) and four arsenic species of high toxicity [As(III), As(V), MMA(V), and DMA(V)] (HS-As) under the influence of HS concentration and pH. Next, the complexing capacity (CC) of HS by As(III) was determined in function of pH, ionic strength and co-existing ions. The free arsenic (Asfree) was determined after a tangential flow ultrafiltration procedure by hydride generation atomic fluorescence spectrometry. The better HS-As interactions for As(III) and As(V) at pH 10.5 reached 52% and 61%, respectively. The increase in pH and ionic strength, as well as co-existing ions increased the CC, which reached 1.57 mg of As(III) g−1 HS. We proposed a HS-As interaction model based on the inner and outer binding sites of HS from these results. The inner sites were occupied through hydrogen bonds, Pearson acid-base, hydrophobic, and van der Waals interactions for trivalent arsenic species, while the interactions through the outer sites for pentavalent arsenic species were mostly by hydrogen bonds and electrostatic forces. According to ecotoxicological studies against Artemia salina, the presence of HS decreased the toxicity of As(III) and As(V) as the lethal concentration increased from 5.81 to 8.82 mg L−1 and from 8.82 to 13.37 mg L−1, respectively. From the results through the proposed model, it was possible to successfully understand the interaction dynamic between soil HS and As(III), As(V), MMA(V) and DMA(V) under simulated environmental conditions.

The interaction between bovine serum albumin (BSA) and thimerosal (TM), an organomercury compound widely employed as a preservative in vaccines, was investigated simulating physiological conditions and using different spectroscopic techniques. The results, employing molecular fluorescence showed the interaction occurs by static quenching through electrostatic forces (ΔH 0), spontaneously (ΔG = −4.40 kJ mol−1) and with a binding constant of 3.24 × 103 M−1. Three-dimensional fluorescence studies indicated that TM causes structural changes in the polypeptide chain of the BSA, confirmed by circular dichroism that showed an increase in α-helix (from 43.9 to 47.8%) content after interaction process. Through synchronized fluorescence and employing bilirubin as a protein site marker, it was confirmed the preferential interaction of TM in the subdomain IB of BSA. The interaction mechanism proposed in this work is based on the reaction of TM with BSA through of free Cys34 residue, forming the adduct BSA-HgEt with the thiosalicylic acid release, which possibly interacts electrostatically with positive side chain amino acids of the modified protein. Finally, it was proven that both TM and EtHgCl accelerate the protein fibrillation kinetics in 42 and 122%, respectively, indicating the toxicity of these compounds in biological systems.

The interaction of (S)-(−)-usnic acid (2) and fumarprotocetraric acid (3), isolated from Cladonia rappii (lichen), and commercial (R)-(+)-usnic acid (1) with urease was investigated in vitro by molecular spectroscopy at pH 7.4 and kinetics experiments using jack bean type III urease. All lichen compounds tested interact with urease by a statistical quenching mechanism forming non-fluorescent complexes that change the native protein structure. Formation of complexes was spontaneous and stabilized mainly by electrostatic forces, in which the interaction magnitude was determined to be 3 < 2 < 1. Compound 2, whose tridimensional structure is disclosed here, acts as a mixed inhibitor while compounds 1 and 3 function as competitive ones. The (R)-(+)-UA (1) is the most efficient lichen metabolite with respect to impairment of the growth of five H. pylori strains. The minimum inhibitory concentrations (MIC) for the lichen metabolites tested were lower (from 2- to 7.8-fold) than those of omeprazole (reference drug) against all H. pylori strains tested. Overall, the lichen metabolites 1–3 are promising lead compounds for the design of more efficient urease inhibitors for the treatment of H. pylori infections.

In this work, we propose an alternative method using MBTH (3-methyl-2-benzothiazolinone hydrazine) as a spectrophotometric probe for the determination of total phenolic compounds. The method is based on the oxidative coupling reaction of MBTH with phenolic compounds in acidic medium to generate a colored product. Under optimum conditions the oxidizing Fe(III) was prepared in H2SO4. The sensitivity of the MBTH method was compared with that of the Folin–Ciocalteu (FC) method for 17 phenolic compounds. Samples of wines (red and white), coffees (instant and brewed), teas and infusions were analyzed by the proposed method and the results were compared with those of FC and 4-AAP (total phenolic compounds) besides ABTS˙+ and DPPH˙ (antioxidant capacity) methods. The results were submitted to a linear correlation analysis at a 95% confidence level, between MBTH and FC (r = 0.9665); MBTH and 4-AAP (r = 0.8425); MBTH and DPPH˙ (r = 0.9667) and MBTH and ABTS˙+ (r = 0.9670). A more detailed analysis was performed according to the different sample classes and we observed that the results of the MBTH method were more consistent with those of DPPH˙ and ABTS˙+ than those of other methods. Thus, the spectrophotometric method developed was characterized as simple and feasible for the samples analyzed and with results comparable to the usual assays.

Graphical abstract, Twenty-five piperidines were studied as potential radical scavengers and antitumor agents. Quantitative interaction of compounds with ctDNA using spectroscopic techniques was also evaluated. Our results demonstrate that the evaluated piperidines possesses different abilities to scavenge the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the anion radical superoxide (•O2−). The piperidine 19 was the most potent radical DPPH scavenger, while the most effective to •O2− scavenger was piperidine 10. In general, U251, MCF7, NCI/ADR-RES, NCI-H460 and HT29 cells were least sensitive to the tested compounds and all compounds were considerably more toxic to the studied cancer cell lines than to the normal cell line HaCaT. The binding mode of the compounds and ctDNA was preferably via intercalation. In addition, these results were confirmed based on theoretical studies. Finally, a linear and exponential correlation between interaction constant (Kb) and GI50 for several human cancer cell was observed.

A new fluorimetric method for copper(II) determination in wines was developed combining functionalized magnetic nanoparticles (FMNP) and fluorescent carbon dots (FCD). To produce FMNP, Fe3O4 was coated with Al2O3 forming Fe3O4@Al2O3 core–shell magnetic nanoparticles and functionalized with PAN and SDS. FCD was synthesized from pineapple juice through hydrothermal carbonization. For copper determination, aliquots of wine, the FMNP dispersion, and Britton-Robinson buffer (pH = 4.0) were mixed under stirring to allow the adsorption of copper by FMNP. Cu-FMNP complex was attracted by a niobium magnet and, after discarding the non-magnetic material, the copper(II) ions were eluted with an FCD dispersion before fluorescence quenching measurements. The proposed method presented a linear range from 0.020 to 0.100 mg L−1 (r2 = 0.9953), RSD (intraday)

Mercury in the aquatic environment can lead to exposure of the human population and is a known toxic metal due to its capacity for accumulation in organs. We aimed to evaluate the mercury level in the blood and urine of fishermen and correlate it with the level of oxidative stress in blood cells. We show in this case-control study that the fishermen of the exposed group (case) of Mundau Lagoon (Maceio - Alagoas, Brazil) have higher concentrations of total mercury in the blood (0.73–48.38 μg L−1) and urine (0.430–10.2 μg L−1) than the total mercury concentrations in blood (0.29–17.30 μg L−1) and urine (0.210–2.65 μg L−1) of the control group. In the blood cells of fishermen, we observed that the lymphomononuclear cells produced high levels of reactive oxygen species (61.7%), and the erythrocytes presented increased lipid peroxidation (151%) and protein oxidation (41.0%) and a decrease in total thiol (36.5%), GSH and the REDOX state (16.5%). The activity of antioxidant system enzymes (SOD, GPx, and GST) was also reduced in the exposed group by 26.9%, 28.3%, and 19.0%, respectively. Furthermore, hemoglobin oxygen uptake was decreased in the exposed group (40.0%), and the membrane of cells presented increased osmotic fragility (154%) compared to those in the control group. These results suggest that mercury in the blood of fishermen can be responsible for causing impairments in the oxidative status of blood cells and is probably the cause of the reduction in oxygen uptake capacity and damage to the membranes of erythrocytes.

The doping of carbon dots (CDs) with non-metallic elements has been a strategy to improve their optical properties and application fields. In the present work, nitrogen and phosphorus-doped CDs (N, P-CDs) were prepared through one-pot hydrothermal synthesis using phytic acid (PA) and L-arginine (Arg) as precursors. The synthesized N, P-CDs were characterized using transmission electron microscopy, FTIR, Raman, UV–vis, and fluorescence spectroscopies. The N, P-CDs exhibited green fluorescence (λem = 515 nm) that can be quenched sensitively and selectively in the presence of Cr(VI), combining static quenching, electron transfer, and an inner filter effect. Consequently, a new fluorescence sensing method applied to Cr(VI) determination was developed using the presently synthesized fluorescent CDs. Under optimized conditions, a linear range from 0.05 to 3 µM in Cr(VI)) was obtained, with a limit of detection of 26 nM. Additionally, the N, P-CDs were selective toward Cr(VI) in the presence of Cr(III) and twenty other species, indicating its potential use to monitor Cr(VI) in environmental samples. Then, Cr(VI) was successfully determined, with recoveries from 85 to 107% in water and soil samples. The method, combining high sensitivity and selectivity, is easy to implement and promotes the use and valorization of eco-friendly materials.

Vessel-inside-vessel microwave-assisted acid digestion was developed for the analysis of samples with high-unsaturated fat content. For the first time, thermal decomposition of (NH4)2S2O8 solutions was evidenced for SO3 generation in situ and gas-phase modification in pressurized digestion flasks. NMR analysis demonstrated the oxidative effect of SO3 on olefin double bonds despite incomplete mineralization of oil samples. In this context, (NH4)2S2O8 decomposition was used in association with HNO3 solutions for sample digestion and mineral determination in edible oils (safflower, coconut, flaxseed, and chia). For all oils, dissolved organic carbon (DOC) contents lower than 5% m m-1 were obtained under optimum conditions: 210 °C with an irradiation time of 40 min, 7.0 mol L-1 HNO3 and 2.0 mol L-1 (NH4)2S2O8 in 0.9 mol L-1 H2SO4. Thus, a DOC reduction of about 70% was reached compared to digestions using only HNO3 at the same conditions. Additionally, a time reduction of up to three-fold was achieved compared to typically demanding edible oil digestions. The proposed method allowed the determination of As, Cd, Cr, Mn, Ni, and Pb in edible vegetable oil samples by ICP-MS. Accuracy was evaluated against the reference method, and no significant difference was observed (p = 0.05), with wide linear ranges and good linearity (r ≥ 0.999) and LOD ranging from 0.48 (As) to 2.41 (Cd) μg L-1.

Filter cake, a residue from the ethanol industry, has a high content of organic matter and presents promising characteristics to act in the remediation of potentially toxic metals. The objective of this paper was to evaluate the characteristics of humic materials extracted from filter cake and investigate their interaction with toxic metals and apply to filter cake in natura and in situ. The complexation capacity of humic matter extracted from filter cakes indicated their high chelating potential and the organic matter importance in potentially toxic metals’ complexation capacity of this type of material. The humic substances extracted from filter cakes showed different affinities for potentially toxic metals (humic material Alagoas: Cr

In this work were synthesized highly luminescent carbon dots for use as fluorescence sensor for Cr(VI). Carbon dots (CDots) were prepared by pyrolysis of the mixture of molecular precursors as citric acid and reduced glutathione. Pyrolysis revealed to be a simple procedure that afforded CDots with a photoluminescence quantum yield of 69.4%, and particle size of about 2.5 nm. To explore the analytical potentiality of the nanomaterial produced, the CDots were applied as fluorescent sensors to determine Cr(VI) in water and soil samples. The interaction mechanism between CDots and Cr(VI) is associated with both inner filter effect and static quenching. After optimization of the main analytical parameters, the method showed a linear range of 0.10–12 μg mL −1 with limit of detection (LOD) of 0.03 μg mL −1 (pH 7), and recoveries of 90–105% and 99.5–107% for samples of water and soil, respectively. Thus, the method proved to be sensitive, fast and versatile for applications in different environmental samples.

The interactions of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) with ovalbumin (OVA), the main allergen protein of egg white, were investigated by molecular spectroscopy and electrophoresis at three pH conditions (1.5, 4.6 and 7.4). Molecular and synchronous fluorescence, UV-vis spectroscopy, electrophoresis and 1H NMR were used to study the interaction process. Tetracyclines interact with ovalbumin fluorescence by a static quenching mechanism with non-fluorescent complex formation changing the native protein structure. The binding constant (Kb) ranged from 2.11 × 104 to 58.4 × 104 L mol−1, and corresponding thermodynamic parameters were measured at different temperatures and pH values. The binding process was spontaneous (ΔG < 0), and the magnitude of the interaction increased in the following order: TC < CTC < OTC. Hydrogen, electrostatic, and Van der Waals forces played a major role in stabilizing the complex. The distances between the donor (protein) and receptors (TC, OTC and CTC) were determined by FRET and varied of 2.95–3.52 nm. Fe(III) and Zn(II) ions increase the affinities of TC and CTC for OVA, while OTC did not suffer a significant influence by the competitor metallic species evaluated.

Thirty-nine Schiff bases were synthesized by performing microwave-assisted condensation of the corresponding aldehydes and aromatic amines. Their reactive nitrogen species (RNS) scavenging activity and inhibitory effects against cancer cell growth were then subsequently investigated. Additionally, the interaction between the calf thymus DNA (ctDNA) and selected Schiff bases was evaluated using fluorescence spectroscopy, and their binding parameters were determined. The yields of the various compounds ranged from moderate to excellent (43-99%) after only a 2-min reaction. The hydroxylated Schiff bases 2, 8, 15, 16, 18, 20, 29, 32, 34, and 37 were found to be potent scavengers of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals with half-maximal scavenging concentration (SC50) values lower than that of the positive control, resveratrol. The presence of hydroxyl substituents on the aromatic rings also proved essential to the cytotoxicity of the compounds. The binding constants (Kb) obtained using fluorescence spectroscopy ranged from 0.37 to 3.07×105Lmol-1, and were strongly influenced by the structure and hydroxylation degree. Schiff bases 3 and 8 showed promising cytotoxic activity, with half-maximal growth inhibitory (GI50) values in the same order of magnitude as those exhibited by the reference drug, doxorubicin against various cell lines. Interestingly, these compounds also showed the highest Kb, suggesting that the cytotoxic activity could be related to their interaction with the DNA of the tumor cells. The results of this study highlighted some Schiff bases as potential lead compounds for the design of new free radical scavengers and anticancer agents.

The interaction of small molecules with DNA has been quite important, since this biomolecule is currently the major target for a wide range of drugs in clinical use or advanced clinical research phase. Thus, the present work aimed to assess the interaction process between the bioactive compound 11a-N-tosyl-5-carba-pterocarpan, (LQB-223), that presents antitumor activity, with DNA, employing spectroscopic techniques, electrophoresis, viscosity and theoretical studies. Through UV-vis and molecular fluorescence spectroscopy, it was possible to infer that the preferential quenching mechanism was static, characterized by non-fluorescent supramolecular complex formation between the LQB-223 and DNA. The binding constant was 1.94∙103Lmol-1 (30°C) and, according to the thermodynamic parameters, the main forces involved in the interaction process are hydrophobic. Potassium iodide assay, competition with ethidium bromide, fluorescence contact energy transfer and melting temperature profile of DNA were employed to evaluate the binding mode. Except for KI assay, all results obtained indicated minor groove as the preferential binding mode of LQB-223 to DNA. These observations were supported by ionic strength assay, viscosity and molecular dynamics and docking studies. Finally, electrophoresis analysis demonstrated that the interaction does not promote DNA fragmentation, but it leads to variation in the migration profile after increasing the ligand concentration.

Background Group B streptococcus (GBS) is the main bacteria that infects pregnant women and can cause abortion and chorioamnionitis. The impact of GBS effects on human trophoblast cells remains largely elusive, and actions toward anti-inflammatory strategies in pregnancy are needed. A potent anti-inflammatory molecule, uvaol is a triterpene from olive oil and its functions in trophoblasts are unknown. We aimed to analyze biomechanical and functional effects of inactivated GBS in trophoblast cells, with the addition of uvaol to test potential benefits. Methods HTR-8/SVneo cells were treated with uvaol and incubated with inactivated GBS. Cell viability and death were analyzed. Cellular elasticity and topography were accessed by atomic force microscopy. Nitrite production was evaluated by Griess reaction. Nuclear translocation of NFkB p65 was detected by immunofluorescence and Th1/Th2 cytokines by bead-based multiplex assay. Results GBS at 10 8 CFU increased cell death, which was partially prevented by uvaol. Cell stiffness, cytoskeleton organization and morphology were changed by GBS, and uvaol partially restored these alterations. Nuclear translocation of NFkB p65 began 15 min after GBS incubation and uvaol inhibited this process. GBS decreased IL-4 secretion and increased IL-1β, IFN-γ and IL-2, whereas uvaol reverted this. Conclusions The increased inflammation and cell death caused by GBS correlated with biomechanical and cytoskeleton changes found in trophoblast cells, while uvaol was effective its protective role. General significance Uvaol is a natural anti-inflammatory product efficient against GBS-induced inflammation and it has potential to be acquired through diet in order to prevent GBS deleterious effects in pregnancy.

Tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC) interactions with the allergenic milk protein casein (CAS) were here evaluated simulating food conditions. The antibiotics assessed interact with CAS through static quenching and form non-fluorescent complexes. At 30 °C, the binding constant (Kb) varied from 0.05 to 1.23 × 106 M−1. Tetracycline interacts with CAS preferably through electrostatic forces, while oxytetracycline and chlortetracycline interactions occur by hydrogen bonds and van der Waals forces. The interaction process is spontaneous, and the magnitude of interaction based on Kb values, followed the order: TC S. aureus, demonstrated that the interaction process possibly alters the biological properties of antibiotics and the own protein, in the food conditions. Communicated by Ramaswamy H. Sarma

Background: Considering the need for the development of new antitumor drugs, associated with the great antitumor potential of thiophene and thiosemicarbazonic derivatives, in this work we promote molecular hybridization approach to synthesize new compounds with increased anticancer activity. Objective: Investigate the antitumor activity and their likely mechanisms of action of a series of N-substituted 2-(5-nitro-thiophene)-thiosemicarbazone derivatives. Methods: Methods were performed in vitro (cytotoxicity, cell cycle progression, morphological analysis, mitochondrial membrane potential evaluation and topoisomerase assay), spectroscopic (DNA interaction studies), and in silico studies (docking and molecular modelling). Results: Most of the compounds presented significant inhibitory activity; the NCIH-292 cell line was the most resistant, and the HL-60 cell line was the most sensitive. The most promising compound was LNN-05 with IC50 values ranging from 0.5 to 1.9 µg.mL-1. The in vitro studies revealed that LNN-05 was able to depolarize (dose-dependently) the mitochondrial membrane, induceG1 phase cell cycle arrest noticeably, promote morphological cell changes associated with apoptosis in chronic human myelocytic leukaemia (K-562) cells, and presented no topoisomerase II inhibition. Spectroscopic UV-vis and molecular fluorescence studies showed that LNN compounds interact with ctDNA forming supramolecular complexes. Intercalation between nitrogenous bases was revealed through KI quenching and competitive ethidium bromide assays. Docking and Molecular Dynamics suggested that 5-nitro-thiophene-thiosemicarbazone compounds interact against the larger DNA groove, and corroborating the spectroscopic results, may assume an intercalating interaction mode. Conclusion: Our findings highlight 5-nitro-thiophene-thiosemicarbazone derivatives, especially LNN-05, as a promising new class of compounds for further studies to provide new anticancer therapies.

Due to the modernization of the agro-industrial sector, compounds with different toxicity and effects on human health and animal have been used and consequently affecting the environment. Among them, tetracycline (TC) stands out as one of the antibiotics most commonly used worldwide. This study evaluated the TC interaction with different fractions of peat in natura and humic substances, humic acid, fulvic acid, and humin. The different fractions of the organic matter were characterized by organic matter content, elemental analysis, spectroscopic analysis (E4/E6), and nuclear magnetic resonance of carbon 13 (NMR 13C), and the interaction between TC and different fractions of organic matter was made by fluorescence spectrometry. We used the tangential ultra-filtration system for determining the complexation capability of humic substances (HSs), fulvic acids (FA), humic acids (HA), and humin (HUM) from peat with TC. Finally, we evaluated sorption kinetic experiments between TC and peat in natura. The peat samples, humic substances, FAs, HAs, and HUM were characterized by organic matter (OM), atomic ratio (H/C and C/O) calculated from elemental analysis data, functional groups quantified by NMR 13C data, and E4/E6 ratio, and the results show significant differences in the structural characteristics of the fractions of OM influenced by the type of microorganisms and environmental factors associated with this decomposition. Data analysis revealed the strongest interaction between HUM and TC (59.19 mg g−1), followed by interaction between HS and TC (43.36 mg g−1 HS). In the sorption studies, these conditions showed the best model to describe the system under consideration using the Freundlich model. The results showed that the different fractions of the OM extracted from peat show different contributions that affect the bioavailability of contaminants to the environment.

Phytic acid (PA) is the main way to store phosphorus in plants, representing about 60–82 % of the total content of phosphorus. The PA determination is still an analytical dare due to low chemical reactivity of this compound. The present work developed a simple and sensitive spectrophotometric method for phytic acid determination on a basis of a colored complex formation between glyoxal bis(2-hydroxianiline) (GBHA) and calcium ions in an alkaline medium (pH 12.5), inhibited by phytic acid presence. The selectivity of the method was evaluated for 15 possible interferences among anions and cations. The main figures of merit from the method in aqueous solution and optimized conditions presented a linear range from 1.0 to 12.5 mg L−1 (n = 8) for analytical curve A = −0.037C PA + 0.72 (r = 0.9981), limit of detection (LOD) equivalent to 0.33 mg L−1, and relative standard deviation (RSD) less than 2.7 %. The proposed method was applied to determine phytic acid in different grain bran/flour samples, the results when compared with reference procedure (Wade method) had no significant difference (significant level of 95 %). Additionally, to explore more applications, the proposed method was employed to determine phytic acid concentration in cream for skin whitening, with recovering of more than 86 %. Therefore, according to the results, the method was versatile with good precision, accuracy, and detection limit similar or better than other works described in the literature.

Propolis e uma mistura complexa de substâncias colhidas por abelhas presentes em exsudados de plantas, cera e polen. O objetivo deste trabalho foi o desenvolvimento e validacao de um metodo analitico para determinacao de micronutrientes em amostras de propoles in natura empregando HR–CS FAAS apos digestao assistida por radiacao micro-ondas. A exatidao do metodo foi demonstrada atraves do uso de material de referencia certificado, ensaio de recuperacao e comparacao dos resultados obtidos com ICP OES. O teste t apresentou concordância a um nivel de 95% para os resultados com material de referencia certificado. O procedimento otimizado propiciou recuperacao na faixa de 86 a 110% dos analitos. O procedimento analitico otimizado foi aplicado em 48 amostras coletadas no estado da Bahia (Brasil).

Biophysical, theoretical and biological in vitro studies were carried out to evaluate the interaction of the main allergen protein of egg white (ovalbumin, OVA) with sulphonamides (SA): sulphathiazole (S1), sulfaquinoxaline (S2), sulfadimethoxine (S3) and sulfamethazine (S4). The binding constants for the OVA-SA supramolecular complexes ranged from 1.20 to 30.66 × 105 M−1, observing the following order of affinity: S1 > S2 > S4 > S3. The preferential forces in the stabilization of the OVA complexes with S2 and S3 were hydrogen bonds and Van der Waals forces, whereas for OVA-S1 and OVA S4, were electrostatic interactions. Interaction process led to a change in the native structure of the protein, which may potentiate its natural allergenicity. Cations Ca(II), Mg(II) and Fe(III) favor the interaction of OVA with S1 and S2. The theoretical studies performed were consistent with the spectroscopic data. Finally, it was found that the interaction process for sulfonamides evaluated with OVA change the inhibition activity profile these antibiotics against strains of Escherichia coli ATCC 25922 and Bacillus megaterium APFSG3isox, but not the minimal inhibitory concentration values.

In this paper, a flow-batch analysis (FBA) system, hydride generation (HG), and atomic fluorescence spectrometry (AFS) are coupled for the first time to develop a fast and sensitive FBA–HG–AFS method for automated inorganic antimony speciation in waters, whether from the sea, mineral water, tap water, or lakes. Unlike previous automated flow methods that use confluent fluids and complex devices, the main advantage of the proposed FBA-HG-AFS method is an innovative use of a simple laboratory made flow-batch chamber to simultaneously perform mixing, homogenization, reactions, antimony hydride formation, and gas–liquid separation. The FBA-HG-AFS method was optimized using two–level full factorial and Box–Behnken designs, and validated on the basis of real repeated measurements and analysis of variance, yielding a satisfactory working range (100–2000 ng L−1), precision (RSD = 4%), sensitivity, and limit of detection (6 ng L−1) for the water samples analyzed. Accuracy was evaluated by recovery tests and analysis of a standard reference material (SRM 1643e) of trace elements in water (NIST, USA), resulting in recovery rates of from 90 to 114%, and relative error = 0.7%. The high sampling throughput (54 speciations h−1), together with low waste generation, low costs, low reagent and sample consumption make this FBA-HG-AFS method an interesting proposal for fast large-scale analysis in routine laboratoy according to the principles of green analytical chemistry.

The cytotoxic activity of the pimarane diterpene annonalide (1) and nine of its semisynthetic derivatives (2–10) was investigated against the human tumor cell lines HL-60 (leukemia), PC-3 (prostate adenocarcinoma), HepG2 (hepatocellular carcinoma), SF-295 (glioblastoma) and HCT-116 (colon cancer), and normal mouse fibroblast (L929) cells. The preparation of 2–10 involved derivatization of the side chain of 1 at C-13. Except for 2, all derivatives are being reported for the first time. Most of the tested compounds presented IC50s below 4.0 μM, being considered potential antitumor agents. The structures of all new compounds were elucidated by spectroscopic analyses including 2D NMR and HRMS. Additionally, the interaction of annonalide (1) with ctDNA was evaluated using spectroscopic techniques, and the formation of a supramolecular complex with the macromolecule was confirmed. Competition assays with fluorescent probes (Hoechst and ethidium bromide) and theoretical studies confirmed that 1 interacts preferentially via DNA intercalation with stoichiometric ratio of 1:1 (1:ctDNA). The ΔG value was calculated as −28.24 kJ mol−1, and indicated that the interaction process occurs spontaneously. Docking studies revealed that van der Walls is the most important interaction in 1-DNA and EB-DNA complexes, and that both ligands (1 and EB) interact with the same DNA residues (DA6, DA17 and DT19).

Made available in DSpace on 2018-12-11T17:13:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The increase in demand for food due to the rapid population growth in recent years has raised the use of fertilizers, particularly phosphate salts. This fact has contributed to the excess amount of phosphorus species in aquatic systems. This is due to the leaching of these species present in the fertilizers applied to the soil to aquatic environments and may lead to eutrophication in these environments. Substances capable of interacting with the phosphate in the aquatic environment are promising for the reduction on the environmental impact. The humin, an insoluble fraction of humic material, has potential for phosphate retention, behaving like a chelating resin. Thus, the purpose of this research was to study the interaction between humin and phosphate. The equilibrium time between humin and phosphate was 15 min, where hydrogenionic potential (pH) 4.0 was the most effective in the interaction process. In this pH, the humin retained 33% of phosphate added. The complexing capacity of the humin-phosphate system was 11.53 mg g−1. The adsorption studies indicated that the system follows a kinetic pseudo-second-order model. The Freundlich model was the most suitable to describe the phosphate adsorption process in humin. To evaluate the humin application in real systems, humin was added to the domestic wastewater. Sixteen percent of the total phosphate was adsorbed by the humin. Based on these results, humin has the potential to phosphate retention in domestic wastewater and could be used as a chelating resin minimizing environmental impact. Federal University of São Carlos (UFSCar) Post-graduate Program in Chemistry and Biotechnology NCEX/PPGQB/UFAL at the Federal University of Alagoas (UFAL), CP 61 Department of Analytical Chemistry Institute of Chemistry São Paulo State University (UNESP), CP 355 Post-graduate Program in Biotechnology and Environmental Monitoring PPGBMA at the Federal University of São Carlos (UFSCar) Department of Analytical Chemistry Institute of Chemistry São Paulo State University (UNESP), CP 355 CNPq: 478361/2013-0

Quantitative interaction of twelve β-carboline derivatives with calf thymus deoxyribonucleic acid (ctDNA) using spectroscopic techniques was evaluated. The values of the binding constants (Kb) obtained for the complexes formed with the ctDNA ranged from 3.30 × 102 to 1.82 × 106 mol L−1, being the β-carbolines with the N,N-dimethylaminophenyl group at position 1 the ones which presented the highest Kb values. The binding mode between the β-carbolines evaluated and ctDNA was proposed from the KI assay, competition with ethidium bromide, and DNA thermal denaturation profile (Tm), where it was possible to infer that the evaluated alkaloids interact with ctDNA preferably via intercalation. Additionally, the correlation of Kb values obtained with the IC50 of seven human cancer cell lines was carried out. From this study, it was possible to observe a linear relation among most of the evaluated derivatives, obtaining r2 values from 0.5360 to 0.9600. In addition, in silico molecular docking was performed to corroborate the experimental results.

Propolis is a complex mixture of substances collected by honeybees from buds or exudates of plants, beeswax, and other constituents, as pollen and sugars. The main purpose of this study was to evaluate two digestion procedures for determination of major, minor, and trace elements (Ba, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn) in natura propolis samples by inductively coupled plasma optical emission spectrometry (ICP OES). The first procedure studied was an open-vessel digestion using HNO3 + H2SO4 + H2O2 in a heating block and the second one was a microwave-assisted concentrated acid digestion using HNO3 + H2O2. Both digestion procedures led to similar results and quantitative recoveries. The residual carbon contents (RCCs) for propolis sample digests were 0.269 ± 0.012 % when using the first procedure with conventional heating and 0.458 ± 0.023 % by microwave-assisted closed vessel digestion, demonstrating high efficiency of both procedures. Accuracy of the results was demonstrated using a certified reference material and by comparison with a recommended official method. The t test (unpaired) at 95 % confidence level showed that there was no significant difference between determined and certified values of all analytes under investigation, except Ca concentration employing conventional procedure. The optimized microwave-assisted digestion procedure led to recoveries around 89–103 % and precision better than 5 % for most samples. The second procedure was faster, safer, and more accurate than the one based on conductive heating. Additionally, principal component analysis (PCA) was applied for checking if there was correlation between inorganic composition and source of propolis samples collected around Bahia State in the Northeast of Brazil.

Submitted by Bruna Fernandes de farias (bruna.fernandes_farias@yahoo.com.br) on 2010-12-22T12:37:33Z No. of bitstreams: 1 2009_OliveiraSantosSantos.pdf.pdf: 234611 bytes, checksum: 82b656f0055b84584948aaaeaebb0408 (MD5) Approved for entry into archive by Claudia Araujo(caraujo@inmetro.gov.br) on 2011-03-31T20:59:48Z (GMT) No. of bitstreams: 1 2009_OliveiraSantosSantos.pdf.pdf: 234611 bytes, checksum: 82b656f0055b84584948aaaeaebb0408 (MD5) Made available in DSpace on 2011-03-31T20:59:48Z (GMT). No. of bitstreams: 1 2009_OliveiraSantosSantos.pdf.pdf: 234611 bytes, checksum: 82b656f0055b84584948aaaeaebb0408 (MD5) Previous issue date: 2009 Um procedimento espectrofotométrico de análise em fluxo foi desenvolvido para determinação de Captopril (CPT) e N-acetil-L-cisteína (NAC) em formulações farmacêuticas baseado na reação com radical iminoquinona produzido pela oxidação de N,N-dimetil-p-fenilenodiamina (DMPD) em meio ácido. A ordem de adição de reagentes foi avaliada e os parâmetros analíticos foram otimizados. As faixas lineares de concentração foram de 2,5-90 e de 5,0-50 mg L-1 para CPT e NAC, respectivamente. Os limites de detecção (3σ) foram calculados em 0,22 e 1,8 mg L-1 e desvios padrão relativos (N = 10) foram inferiores que 1,0 e 2,1% para CPT e NAC, respectivamente. O procedimento foi empregado para a determinação de CPT e NAC em diversas formulações farmacêuticas e os resultados concordaram com os obtidos pelos métodos de referência para 95% de confiabilidade aplicando teste-t pareado. ____________________________________________________________________________________. ABSTRACT - A spectrophotometric flow analysis procedure to determine Captopril (CPT) and N-acetyl-L-cysteine (NAC) in pharmaceutical formulations was developed based on the reaction with iminoquinone radical produced from the N,N-dimethyl-p-phenilenediamene (DMPD) oxidation in acid medium. The reagents addition order was evaluated and analytical parameters were optimized. The linear concentrations ranges were 2.5-90 and 5.0-50 mg L-1 for CPT and NAC, respectively. Limits of detection (3σ) were calculated at 0.22 and 1.8 mg L-1 and the relative standard deviation (N = 10) were lower than 1.0 and 2.1% for CPT and NAC, respectively. The procedure was employed for CPT and NAC determination in diverse pharmaceutical formulations and by applying paired t-test the results were in agreement with those obtained by reference methods for 95% confidence level. 7 p. : il.