Helena Becker

Brazilian fruit pulps as functional foods and additives: Evaluation of bioactive compounds

Eight tropical fruit pulps from Brazil were simultaneously characterised in terms of their antioxidant and antimicrobial properties. Antioxidant activity was screened by DPPH radical scavenging activity (126-3987 mg TE/100g DW) and ferric reduction activity power (368-20819 mg AAE/100g DW), and complemented with total phenolic content (329-12466 mg GAE/100g DW) and total flavonoid content measurements (46-672 mg EE /100g DW), whereas antimicrobial activity was tested against the most frequently found food pathogens. Acerola and açaí presented the highest values for the antioxidant-related measurements. Direct correlations between these measurements could be observed for some of the fruits. Tamarind exhibited the broadest antimicrobial potential, having revealed growth inhibition of Pseudomonas aeruginosa. Escherichia coli, Listeria monocytogenes, Salmonella sp. and Staphylococcus aureus. Açaí and tamarind extracts presented an inverse relationship between antibacterial and antioxidant activities, and therefore, the antibacterial activity cannot be attributed (only) to phenolic compounds.

The influence of castanhão reservoir on nutrient and suspended matter transport during rainy season in the ephemeral Jaguaribe river (CE, Brazil)

Measurements of nutrient and suspended matter concentrations and loads entering and leaving the Castanhão reservoir during the rainy season were carried out to assess the influence of this large reservoir on land-sea fluvial transport in the ephemeral Jaguaribe river basin. Spatial variation indicated statistically significant attenuation of concentrations only for total phosphorous and suspended matter across the reservoir. Strong retention of nutrients and suspended matter loads by the reservoir was observed with average trapping efficiency of 89% for dissolved silicon, 98% of soluble reactive phosphorus, 71% for ammonium, 87% for total nitrogen, 98% for total phosphorus and 97% for suspended matter compared to the reservoir inflow. The dam operational procedure defined by the ephemeral conditions of the river reduced water releases compared to reservoir inflow and induced strong retention of nutrient and suspended matter loads within the reservoir when fluvial transfer occurs in this semiarid watershed.

Influence of river discharge on phytoplankton structure and nutrient concentrations in four tropical semiarid estuaries

Neste estudo foram avaliados os efeitos do aumento da vazao fluvial sobre o fitoplâncton e os nutrientes em quatro estuarios do Nordeste do Brasil. Para isso, foram coletadas amostras durante um periodo de forte deficit hidrologico (Nov/2010, periodo seco), e durante um periodo chuvoso (maio/2011). Dois estuarios estao localizados em areas urbanas (Ceara - CE e Coco - CO) e dois tem forte deficit de agua doce (Pacoti - PAC e Priangi - PIR). Os efeitos do aumento da descarga fluvial foram diferentes entre os que recebem descargas antropicas (CO, CE e PIR) e aquele menos impactado (PAC). No CO e CE, o fluxo fluvial no periodo chuvoso diluiu os nutrientes e controlou as floracoes fitoplanctonicas. No PIR, o fosforo e o nitrogenio inorgânico decresceram neste periodo. Foi observado um aumento de todos os nutrientes no PAC, e de NT no PIR, seguidos de um aumento do fitoplâncton. No periodo chuvoso, especies dulcicolas de ambientes eutroficos dominaram nos estuarios. No periodo seco, observaram-se floracoes de Cryptomonas/Rhodomonas (CE) e Synechocystis aquatilis (CO). No periodo seco, sob a condicao de hipersalinidade, predominaram especies marinhas no PAC e PIR. A Analise de Correspondencia Canonica sugeriu a salinidade, a silica e o NT como os principais responsaveis pela variacao do fitoplâncton.

Chitosan/mangiferin particles for Cr(VI) reduction and removal

In this work, chitosan/mangiferin particles (CMP) were prepared by spray-drying technique and characterized by SEM, DLS, FTIR, HPLC-UV and adsorption studies to investigate a possible application as a preventive material in cases of human and animal contamination with Cr(VI). CMP presented sizes ranging from nano to micrometers. Chitosan and mangiferin (MA) presence in the powder was confirmed by FTIR and MA quantification (136 μg/mg) was performed using a calibration curve prepared by HPLC-UV. Adsorption capacity of Cr(VI) onto CMP was compared with chitosan and investigated in a batch system by considering the effects of various parameters like contact time, initial concentration of adsorbent and pH. Cr(VI) removal is pH dependent and it was found to be maximum at pH 5.0. The results showed that CMP has a potential application as a preventive material in cases of human or animal contamination with Cr(VI).

Direct electrochemical analysis of dexamethasone endocrine disruptor in raw natural waters

This paper describes an electroanalytical methodology using square-wave adsorptive voltammetry, which has been successfully applied for the direct determination of dexamethasone residues in raw natural waters used for the public supply of the Ceara State, Brazil. The obtained detection limits ranged from 7.47 × 10-9 to 1.80 × 10-8 mol L-1 for the three matrices of raw natural waters evaluated. High percentages of average recovery (98.86% ± 0.72), repeatability (0.32% ± 0.05) and reproducibility (0.91% ± 0.20) were obtained in these samples, reaffirming the sensitivity of the procedure. Energy of the LUMO orbitals and Mulliken’s atomic charges were calculated using the functional BLYP/DNP. The theoretical results allied to the diagnostic criteria of the square-wave voltammetry indicate that the dexamethasone redox mechanism is associated to the quasi-reversible and irreversible reduction process of the ketone groups located at C-20 and C-3, respectively.

Analytical determination of nimesulide and ofloxacin in pharmaceutical preparations using square-wave voltammetry

The electrochemical behaviour and analytical detection procedure for nimesulide (NIM) and ofloxacin (OFX) and their assay in commercial formulations were evaluated using square-wave voltammetry (SWV) combined with a hanging mercury drop electrode (HMDE). All experimental and voltammetric conditions were previously optimized to obtain the best analytical signal in terms of intensities and profile of the reduction peaks. For NIM, the peak currents were related to the one-electron reduction of a nitro group to a stable radical anion, which is followed by a one-electron transfer and a protonation step with a consequent formation of a nitrosoanion. The voltammetric results indicated that the mechanism of OFX involved the transfer of two electrons and two protons in a totally irreversible reduction related to the conversion of a ketone group to an alcohol group. Analytical parameters such as linearity range, equations of the analytical curves, correlation coefficients, detection and quantification limits, recovery efficiency, and relative standard deviation for repeatability and reproducibility experiments were compared to similar results obtained by the use of UV-Vis spectrophotometry, and the results showed that the voltammetric procedure using HMDE is suitable to determine pharmaceutical compounds in complex samples. The applicability of the proposed procedure was tested on pharmaceutical formulations of NIM and OFX by observing the stability, specificity, recovery and precision of the procedure in tablets, oral solution and ophthalmic solution.

Adsorption of Safranin on Pseudostem Banana Fibers

Adsorption assays indicated that the pseudostem banana fibers are an efficient sorbent for the removal of safranin from aqueous solution being dependent on pH, dye concentration, and temperature. Kinetics and thermodynamic studies indicated Sips isotherm as the most suitable model to describe the studied adsorption process, which occurs through a pseudo second-order process. The thermodynamic parameters indicated that the sorption of safranin dye onto pseudostem banana fiber is spontaneous (ΔGads ≅ –30 kJ mol−1) and exothermic (ΔHads ≅ –17 kJ mol−1).

BIOSSENSOR ELETROQUÍMICO BASEADO NA ENZIMA TIROSINASE PARA A DETERMINAÇÃO DE FENOL EM EFLUENTES

This work describes the development of a biosensor based on the tyrosinase enzyme (Tyr) for the determination of phenol (PHEN) in laboratory effluent samples derived from ammoniacal nitrogen analysis of the water samples from the Muquem dam in the city of Carius, CE, using square-wave voltammetry (SWV). The electrode modification consisted of the immobilization of gold nanoparticles, multi-walled carbon nanotubes, cobalt phthalocyanine, and Tyr on a glassy carbon electrode. The electrolyte, pH, enzyme quantity, and voltammetric parameters were optimized to detect PHEN. The analytical curves presented a linear range from 4.97 × 10-6 mol L-1 to 6.10 × 10-5 mol L-1, and the detection limit (DL) and quantitation limit (QL) values were 4.81 × 10-6 mol L-1 and 4.97 × 10-6mol L-1, respectively. The repetition of measurements with the same biosensor and repetition for three other prepared biosensors exhibited a relative standard deviation (RSD) of 5.50 and 1.75%, respectively. The percentage recovery of PHEN in effluent samples varied from 86.40 to 105.04%. The stability of the biosensor was evaluated (at 21 days) with satisfactory results, showing 97.86% of the initial response. Moreover, the DL and recovery percentages agreed with the established values from CONAMA and ABNT, respectively. Thus, the electrode configuration developed seems a promising tool in the detection and quantification of PHEN in complex samples.

The influence of the structural features of lignin-based polyurethane coatings on ammonium sulfate release: kinetics and thermodynamics of the process

The influence of the properties of lignin-based polyurethane (PU) coatings on the release behavior of ammonium sulfate was assessed through complete physicochemical, structural, and morphological characterization. The influence of the release medium was evaluated as well. The higher the amount of lignin in the coatings was, the lower the pore diameter and swelling degree and the higher crosslinking were. The hydrophobicity of coatings was not significantly changed by increasing the lignin content. However, the opposite behavior was observed for their biodegradability. The results of the nutrient release experiments showed that the two formulations of lignin-based PUs had very similar behavior in terms of release rates of NH4+ and SO42− in both release media, despite their different properties. However, there was a difference between their release rate constants obtained by using three different kinetic models. In addition, both PU coatings released a higher amount of SO42− than NH4+ in both media. The thermodynamic data suggest that dissolution and release processes for SO42− are more spontaneous than that for NH4+. Nevertheless, both coatings behaved in accordance with CEN standards for CRF systems, representing a potential technique for agricultural applications.

Application of the QuEChERS method for the determination of organochlorine pesticide residues in Brazilian fruit pulps by GC-ECD

ABSTRACT The Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method was applied to the extraction of 14 organochlorine pesticides (OCPs) residues from commercial fruit pulps available in supermarkets in Fortaleza, Northeastern Brazil. The analyses were carried out by gas chromatography (GC), coupled to an electron-capture detector (ECD), and were confirmed by GC-tandem mass spectrometry (MS). The parameters of the analytical method, such as accuracy, precision, linear range, limits of detection and quantification, were determined for each pesticide. The results showed good linearity (R2 ≥ 0.9916) and the overall average recoveries were considered satisfactory obtaining values between 69 and 110%, RSD of 2–15 %, except for hexachlorobenzene (HCB) in açai, acerola and guava pulp samples. The OCPs were detected in guava (α–HCH; lindane) and soursop (α, β–HCH isomers) samples. The QuEChERS method and GC–ECD were successfully used to analyze OCPs in commercially available Brazilian fruit pulps and can be applied in routine analytical laboratories.