Papers by María Fernanda Silva
Food Chemistry, 2016
An analytical method has been developed to determine seleno-amino acids in proteins extracted fro... more An analytical method has been developed to determine seleno-amino acids in proteins extracted from extra virgin olive oils (EVOOs). Different aqueous/organic solvents were tested to isolate proteins, an acetone:n-hexane combination being the best protein precipitant. In a first dimension chromatography, extracted proteins were analysed by size exclusion chromatography (SEC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) to identify S and Se associations as proteins marker. Two fractions of 66kDa (A) and 443kDa (B) were identified. These fractions were submitted to microwave-assisted acid hydrolysis (MAAH) to release seleno-amino acids. In a second dimension chromatography seleno-amino acids were determined by reversed-phase chromatography (RPC) coupled to ICP-MS. Seleno-methylselenocysteine was determined with values ranging from 1.03-2.03±0.2μgkg(-1) and selenocysteine at a concentration of 1.47±0.1μgkg(-1). Variations of protein and seleno-amino acid concentrations were observed between EVOO varieties, contributing to EVOO cultivar differentiation.
Sustainable Chemistry and Pharmacy
Food Chemistry, 2022
Basil is an edible, aromatic plant, which makes the study of the ecotoxicity of metals in plant m... more Basil is an edible, aromatic plant, which makes the study of the ecotoxicity of metals in plant metabolism relevant. Given the above, the objective of this study was to evaluate the effects of metals, aluminum, lead, and cadmium, in the synthesis of phenolic compounds and in the dry mass of basil plants (O. basilicum L.) grown in a hydroponic system. The plants were subjected to four different concentrations of cadmium (0.2, 0.6, 1.2, and 1.8 mmol L-1), lead and aluminum (0.04, 0.08, 0.12, and 0.16 mmol L-1), and compared with the control. After desiccation of the plant material, the total dry mass was obtained and then, hydroethanolic extracts (43% distilled water and 57% ethanol) were made for biochemical analyzes, which consisted of the determination of caffeic acid (CA) and rosmarinic acid (RA) by high performance liquid chromatography analysis with a diode detector (HPLC-DAD); total phenolics (TP) and total flavonoids (TF) by spectrophotometry. The data were submitted to analysis of variance and multivariate analysis (principal component analysis-PCA and hierarchical cluster analysis-HCA) was applied for data association. The phenolic compounds showed a high positive correlation with each other, and the total dry mass showed low and negative correlations with the analyzed variables. The results showed that the metals aluminum, lead, and cadmium promoted a stress condition in basil plants, which resulted in the reduction of the dry matter mass and an increase in the synthesis of phenolic compounds, according to the type and concentration of the metal.
Botrytis cinerea is a ubiquitous fungus causing gray mold, the main postharvest disease in fruit,... more Botrytis cinerea is a ubiquitous fungus causing gray mold, the main postharvest disease in fruit, which implies important economic losses in agriculture. With growing concern over health and environmental effects of pesticides, the search for eco-friendly alternatives is a clear priority. Plant extracts represent a rich source of biocompounds with attractive antimicrobial properties. In the last decade, Natural Deep Eutectic Solvents (NADES) has emerged as an auspicious green extraction media to achieve bioextract for a sustainable postharvest control. In the present study, a novel L. cuneifolia NADES-based bioextract was evaluated against B. cinerea. To this purpose, a NADES composed by lactic acid, glucose and water (LGH) was used as extracting agent and compared with traditional solvents in terms of antioxidant capacity and total phenolic content. Furthermore, the bioextract antifungal activity was tested in vitro and also in vivo on artificially inoculated grapes, in order to obtain preliminary data about the efficacy on gray mold development. The antimicrobial activity of the bioextract was assessed using agar diffusion method against B. cinerea, inhibition of 92% was achieved with the bioextract at 2%. Notably, L. cuneifolia bioextract showed an excellent performance for gray mold control on grapes, supporting their potential as alternative green fungicide. Keywords natural deep eutectic solvents • biocompounds • antimicrobial activity • medicinal plant • postharvest control J. Boiteux et al.
Comprehensive Foodomics, 2021
Analytical and Bioanalytical Chemistry, 2021
Current trends in analytical chemistry encourage the use of innocuous solvents to develop modern ... more Current trends in analytical chemistry encourage the use of innocuous solvents to develop modern methods aligned with green chemistry. In this sense, natural deep eutectic solvents (NADESs) have emerged as a novel generation of green solvents which can be employed in sample treatments as an alternative to the toxic organic solvents commonly used so far. In this work, a new extraction method employs dispersive liquid-liquid microextraction based on a solid floating organic droplet (DLLME-SFO), by using a mixture composed of a less dense than water extraction solvent, 1-dodecanol, and a novel dispersive solvent, NADES. The methodology was proposed to extract and preconcentrate some pesticide residues (fipronil, fipronil-sulfide, fipronil-sulfone, and boscalid) from environmental water and white wine samples before analysis by liquid-chromatography coupled to ultraviolet detection (HPLC-UV). Limits of quantification (LOQs) lower than 4.5 μg L−1, recoveries above 80%, and precision, expressed as RSD, below 15% were achieved in both samples showing that the proposed method is a powerful, efficient, and green alternative for the determination of these compounds and, therefore, demonstrating a new application for NADES in sample preparation. In addition, the DLLME-SFOD-HPLC-UV method was evaluated and compared with other reported approaches using the Analytical GREEnness metric approach, which highlighted the greenness of the proposed method.
Microchemical Journal, 2020
In the present work, a method based on the Ultrasound-dispersive liquid-liquid microextraction (U... more In the present work, a method based on the Ultrasound-dispersive liquid-liquid microextraction (US-DLLME) for the preconcentration of melatonin in Brazilian and Argentinian wine samples prior to the determination by reverse phase high performance liquid chromatography with diode array detector HPLC-DAD was developed. Sample prep optimization was carried out in two stages. First, a full factorial design was executed to evaluate the variables significance. The second step consisted of significant variables optimization (pH, extraction volume, sonication time, centrifugation time) using a Doehlert matrix to determine the critical values. Optimal US-DLLME extraction conditions were as follows: pH of 4.5, sonication time of 6.8 min, centrifugation time of 2.5 min, extractor volume of 250 µL and 5.0 mL of sample. The organic phase was retrieved with a microsyringe to a glass tube, dried and diluted with the mobile phase prior injection. The method presented a limit of detection (LOD) of 0.23 μg L −1 and a limit of quantification (LOQ) of 0.70 μg L −1. The precision expressed as relative standard deviation (R.S.D.) was 0.8% and 1.9% at 10.0 and 1.0 μg L −1 , respectively. Accuracy was confirmed by comparison of the results found by the proposed methods with an alternative method, and spike tests with recuperations ranging from 92 to 103%. The analyzed samples showed concentrations varying from 2.2 to 5.0 μg L −1 .
Microchemical Journal, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Phyton, 2017
Efecto de compuestos fenólicos presentes en extractos de plantas argentinas en el crecimiento mic... more Efecto de compuestos fenólicos presentes en extractos de plantas argentinas en el crecimiento miceliar del fitopatógeno Botrytis cinerea Pers.
RSC Advances, 2019
Electrochemical reduction of CO2 on paper-derived carbon electrodes modified with metallic nanopa... more Electrochemical reduction of CO2 on paper-derived carbon electrodes modified with metallic nanoparticles.
Microchemical Journal, 2018
A theoretical and experimental study was performed on natural deep eutectic solvents (NADES) form... more A theoretical and experimental study was performed on natural deep eutectic solvents (NADES) formed by lactic acid-glucose (LGH), citric acid-fructose (CFH), and citric acidglucose (CGH). The presence of nuclear Overhauser effect (NOE) in the proton nuclear magnetic resonance (1 H NMR) spectra of the NADES was studied. The spatial proximity between the NADES components was experimentally confirmed by the detection of multiple NOE effects in the dilutions analyzed. LGH showed the best outcome by partially maintaining theirits supramolecular structure throughout the dilutions. In order to rationalize the intermolecular interactions generated among the components, a theoretical study was performed using a density functional theory (DFT) computational method. A simplified dimeric model of the NADES was selected in order to achieve a rapid screening of the system searching for interactions between their constituents. In agreement with the experimental evidence, the calculations allowed to confirm the spatial proximity, by finding at least two hydrogen bonds between the components of every NADES.
ELECTROPHORESIS, 2017
A novel methodology is presented for the enhanced electrochemical detection of oleuropein in comp... more A novel methodology is presented for the enhanced electrochemical detection of oleuropein in complex plant matrices by Graphene Oxide Pencil Grahite Electrode (GOPGE) in combination with a buffer modified with a Natural Deep Eutectic Solvent, containing 10% (v/v) of Lactic acid, Glucose and H 2 O (LGH). The electrochemical behavior of oleuropein in the modified-working buffer was examined using differential pulse voltammetry. The combination of both modifications, NADES modified buffer and nanomaterial modified electrode, LGH-GOPGE, resulted on a signal enhancement of 5.3 times higher than the bare electrode with unmodified buffer. A calibration curve of oleuropein was performed between 0.10 to 37 M and a good linearity was obtained with a correlation coefficient of 0.989. Detection and quantification limits of the method were obtained as 30 and 102 nM, respectively. In addition, precision studies indicated that the voltammetric method was sufficiently repeatable, %RSD 0.01 and 3.16 (n = 5) for potential and intensity, respectively. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract prepared by ultrasound-assisted extraction. The results obtained with the proposed electrochemical sensor were compared with Capillary Zone Electrophoresis analysis with satisfactory results.
Plant physiology and biochemistry : PPB, Jan 8, 2017
Soluble carbohydrates distribution depends on plant physiology and, among other important factors... more Soluble carbohydrates distribution depends on plant physiology and, among other important factors, determines fruit yield and quality. In plant biology, the analysis of sugars is useful for many purposes, including metabolic studies. Capillary electrophoresis (CE) proved to be a powerful green separation technique with minimal sample preparation, even in complex plant tissues, that can provide high-resolution efficiency. Matrix effect refers to alterations in the analytical response caused by components of a sample other than the analyte of interest. Thus, the assessment and reduction of the matrix factor is fundamental for metabolic studies in different matrices. The present study evaluated the source and levels of matrix effects in the determination of most abundant sugars in grapevine tissues (mature and young leaves, berries and roots) at two phenological growth stages. Sucrose was the sugar that showed the least matrix effects, while fructose was the most affected analyte. Base...
Analytica Chimica Acta, 2016
New trends in analytical chemistry encourage the development of smart techniques and methods alig... more New trends in analytical chemistry encourage the development of smart techniques and methods aligned with Green Chemistry. In this sense, Natural Deep Eutectic Solvents represents an excellent opportunity as a new generation of green solvents. In this work a new application for them has been proposed and demonstrated. These solvents were synthesized by combinations of inexpensive and natural components like, Glucose, Fructose, Citric acid and Lactic acid. The different natural solvents were easily prepared and added to buffer solution in different concentrations, allowing the enhancement of electrochemical detection of an important representative antioxidant like quercetin (QR) with improved signal up to 380%. QR is a ubiquitous flavonoid widespread in plants and food of plant origin. The proposed method using phosphate buffer with a eutectic mixture of Citric acid, Glucose and water in combination with carbon screen printed electrodes exhibited a good analytical performance. Detection and quantification limits were of 7.97 and 26.3 nM respectively; and repeatability with %RSDs of 1.41 and 7.49 for peak potential and intensity respectively. In addition, it has proved to be faster, greener and cheaper than other sensors and chromatographic methods available with the additional advantage of being completely portable. Furthermore, the obtained results demonstrated that the proposed method is able for the determination of QR in complex food samples.
TrAC Trends in Analytical Chemistry, 2016
Highlights NADES offer excellent skills as green solvents for their use at different steps of a... more Highlights NADES offer excellent skills as green solvents for their use at different steps of any analytical method NADES have the advantages of low vapour pressure, nonvolatility, low toxicity, nonflammability, good thermal stability, wide liquid range, good biodegradability and ability to be reutilized. The possible combinations of starting materials provides a powerful tool to achieve tailor made solvents Preparation, chemical structure, analytical applications as well as future perspectives are discussed
Microchimica Acta, 2015
Single-walled carbon nanotubes (SWCNT), multiwalled carbon nanotubes (MWCNT) and graphene have be... more Single-walled carbon nanotubes (SWCNT), multiwalled carbon nanotubes (MWCNT) and graphene have been tested as carbon allotropes for the modification of carbon screen-printed electrodes (CSPEs) to simultaneously determine melatonin (MT) and serotonin (5-HT). Two groups of CSPEs, both 4 mm in diameter, were explored: The first includes commercial SWCNT, MWCNT and graphene, the second includes SWCNT, MWCNT, graphene oxide nanoribbons and reduced nanoribbons that were drop casted on the electrodes. The carbon nanomaterials enhanced the electroactive area in the following order: CSPE <MWCNTs <SWCNTs <graphene. This allowed the simultaneous determination of 5-HT and MT at the working potentials of + 50 mV and +390 mV (vs. Ag), respectively. The use of carbon nanomaterials, in particular of graphene oxide nanoribbons on CSPEs, represents an excellent and disposable tool for sensing the two target molecules in even small sample volumes. Figures of merit for MT and 5-HT include (a) detection limit of 1.1 and 0.4 μM for MT and 5-HT, respectively; (b) an inter-electrode reproducibility with RSD ≤ 8 %; (c) 120 s response time, and (d) recoveries (in case of spiked samples) ranging from 94 to 103 % (with an RSD < 1 %). Keywords Screen-printed electrode. Carbon nanomaterials. Single and multi-walled carbon nanotubes. Graphene. Graphene nanoribbons. Melatonin. Serotonin
Microchemical Journal, 2015
In this study, a simple and solvent-free method using headspace solid-phase microextraction (SPME... more In this study, a simple and solvent-free method using headspace solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) was developed for determination of the volatile compounds from fresh flowers and nectar of male sterile and fertile lines of Allium cepa L. The SPME parameters were studied; the optimum conditions of 85 μm carboxen/polydimethylsiloxane (CAR/PDMS), extraction temperature of 30°C and extraction time of 30 min were obtained. The analytical method was applied to characterize different onion lines according to the chemical composition of the volatile fraction of nectar and flowers. On the other hand, it was determined which odor components contribute to the pollination of onions lines and relate the content of specific analytes with foraging behavior and seed production. More than 90 compounds were identified. The samples studied showed differences in the volatile profiles of flowers and nectar among the different lines. The results demonstrated that headspace SPME-GCMS is a simple, rapid and solvent-free method suitable for analysis of volatile compounds emitted from onion plants. Furthermore, a great difference was found for the number of bee visits and seed yield among the onion lines analyzed. This study demonstrates that the combination of chemical information and statistical analysis is able to differentiate onion male sterile lines from fertile lines, as well as among male sterile lines. Repellent compounds, such as dioxolanes, piperidines and organosulfurs may contribute negatively to pollination, since the higher content of these analytes, the less bee visits and seed production yield.
Uploads
Papers by María Fernanda Silva