This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The availability of fast and non-expensive analytical methods for the determination of widespread... more The availability of fast and non-expensive analytical methods for the determination of widespread interest analytes such as glucose is an object of large relevance; this is so not only in the field of analytical chemistry, but also in medicinal and in food chemistry. In this context, electrochemical biosensors have been proposed in different arrangements, according to the mode of electron transfer between the bioreceptor and the electrode. An efficient immobilization of an enzyme on the electrode surface is essential to assure satisfactory analytical performances of the biosensor in terms of sensitivity, limit of detection, selectivity, and linear range of employment. Here, we report the use of a thiophene monomer, (2,5-di(2-thienyl)thieno [3,2-b]thiophene (dTT-bT), as a precursor of an electrogenerated conducting film to immobilize the glucose oxidase (GOx) enzyme on Pt, glassy carbon (GC), and Au electrode surfaces. In addition, the polymer film electrochemically synthetized on a ...
Despite unifloral honeys from Sardinia, Italy, being appreciated worldwide for their peculiar org... more Despite unifloral honeys from Sardinia, Italy, being appreciated worldwide for their peculiar organoleptic features, their elemental signature has only partly been investigated. Hence, the principal aim of this study was to measure the concentration of trace and toxic elements (i.e., Ag, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Sn, Sr, Te, Tl, V, and Zn) in four unifloral honeys produced in Sardinia. For this purpose, an original ICP-MS method was developed, fully validated, and applied on unifloral honeys from asphodel, eucalyptus, strawberry tree, and thistle. Particular attention was paid to the method’s development: factorial design was applied for the optimization of the acid microwave digestion, whereas the instrumental parameters were tuned to minimize the polyatomic interferences. Most of the analytes’ concentration ranged between the relevant LoDs and few mg kg−1, while toxic elements were present in negligible amounts. The elemental signatures of asp...
We evaluate the influence of the use of different titania precursors, calcination rate, and ligan... more We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(O i Pr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and
5-(hydroxymethyl)furan-2-carbaldehyde, better known as hydroxymethylfurfural (HMF), is a well-kno... more 5-(hydroxymethyl)furan-2-carbaldehyde, better known as hydroxymethylfurfural (HMF), is a well-known freshness parameter of honey: although mostly absent in fresh samples, its concentration tends to increase naturally with aging. However, high quantities of HMF are also found in fresh but adulterated samples or honey subjected to thermal or photochemical stresses. In addition, HMF deserves further consideration due to its potential toxic effects on human health. The processes at the origin of HMF formation in honey and in other foods, containing saccharides and proteins—mainly non-enzymatic browning reactions—can also produce other furanic compounds. Among others, 2-furaldehyde (2F) and 2-furoic acid (2FA) are the most abundant in honey, but also their isomers (i.e., 3-furaldehyde, 3F, and 3-furoic acid, 3FA) have been found in it, although in small quantities. A preliminary characterization of HMF, 2F, 2FA, 3F, and 3FA by cyclic voltammetry (CV) led to hypothesizing the possibility ...
We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated ... more We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance but different electronic properties. As a result, the reactivity of the two series of complexes follows very different routes. In particular, the new complexes behave differently towards protonation reactions, differences given by substituents and ancillary ligands, added to the presence of several nucleophilic centers. Reaction of complex [Pt(bpy6OMe-H)(PPh3)Me)] with [H3O⋅18-crown-6][BF4] results in a retro-rollover reaction whose final product is the cationic adduct [Pt(bpy6OMe)(PPh3)Me)]+. Surprisingly, only the isomer with the cis-PPh3-OMe geometry is formed; in spite of an expected instability due to steric hindrance, Density-Functional theory (DFT...
Enzyme-based amperometric biosensors are proving to be important analytical tools in several fiel... more Enzyme-based amperometric biosensors are proving to be important analytical tools in several fields such as food, environmental and, in recent years, the biomedical one. This work describes the use of 4,7-bis(5-(pyridin-2-yl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TBT) in the development of a tyrosinase-based biosensor for epinephrine detection. The modifying agent was obtained as a film by electrochemical oxidation of TBT on a gold disk electrode. Electrochemical characterization and scanning electrode microscopy (SEM) images suggest the formation of a conducting film on the electrode surface. Tyrosinase from mushroom was then immobilized by a mixed technique of adsorption and cross-linking. Glutaraldehyde was used as a coupling agent. The obtained device shows a very good linear response (0.1-50 μM) with a LoD value of 0.06 μM and a LoQ of 0.09 μM. Moreover, good selectivity towards some typical interferents (namely, ascorbic acid, tryptophan, uric acid and L-cysteine) and satisfactory recoveries have been observed.
The lack of interest in the determination of toxic elements in liquids for electronic cigarettes ... more The lack of interest in the determination of toxic elements in liquids for electronic cigarettes (e-liquids) has so far been reflected in the scarce number of accurate and validated analytical methods devoted to this aim. Since the strong matrix effects observed for e-liquids constitute an exciting analytical challenge, the main goal of this study was to develop and validate an ICP-MS method aimed to quantify 23 elements in 37 e-liquids of different flavors. Great attention has been paid to the critical phases of sample pre-treatment, as well as to the optimization of the ICP-MS conditions for each element and of the quantification. All samples exhibited a very low amount of the elements under investigation. Indeed, the sum of their average concentration was of ca. 0.6 mg kg−1. Toxic elements were always below a few tens of a μg per kg−1 and, very often, their amount was below the relevant quantification limits. Tobacco and tonic flavors showed the highest and the lowest concentrati...
Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reactio... more Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C–H bond is regioselectively activated, affording an uncommon cyclometalated complex, called “rollover cyclometalated complex”. The key of the process is the internal rotation of the ligand, which occurs before the C–H bond activation and releases from coordination a donor atom. The new “rollover” ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C–H bond is usually in a symmetric positi...
The amount of specific trace elements like selenium (Se) may be of health concern for humans if c... more The amount of specific trace elements like selenium (Se) may be of health concern for humans if contained in too high (or low) quantities in staple foods like rice. Among the attempts aimed to optimize the Se concentration in rice, only few studies have been focused on the use of irrigation methods other than continuous flooding. Since intermittent irriguous methods, like sprinkler and saturation, have found to be effective in modifying the bioaccumulation of arsenic and cadmium in rice kernels, the main goal of this study is to measure the amount of the total Se contained in grains of 26 rice genotypes cultivated for two consecutive agrarian vintages in the same open field and with the same water, but differently irrigated with continuous flooding, sprinkler or saturation. To do this, an original and validated ICP-MS method has been developed. The validation parameters accounted for a high sensitivity and accuracy. Sprinkler irrigation is able to reduce in the average of 90% the am...
Structure-related biological activities of flavanones are still considered largely unexplored. Si... more Structure-related biological activities of flavanones are still considered largely unexplored. Since they exhibit various medicinal activities, it is intriguing to enter deeper into their chemical structures, electronic transitions or interactions with some biomolecules in order to find properties that allow us to better understand their effects. Little information is available on biological activity of flavanone and its monohydroxy derivatives in relation to their physicochemical properties as spectral profiles, existence of protonated/deprotonated species under pH changes or interaction with Calf Thymus DNA. We devoted this work to research demonstrating differences in the physicochemical properties of the four flavanones: flavanone, 2′-hydroxyflavanone, 6-hydroxyflavanone and 7-hydroxyflavanone and linking them to their biological activity. Potentiometric titration, UV–Vis spectroscopy were used to investigate influence of pH on acid–base and spectral profiles and to propose the ...
Traditional Filuferru is an ancient spirit from Sardinia, Italy, usually obtained from the distil... more Traditional Filuferru is an ancient spirit from Sardinia, Italy, usually obtained from the distillation of wine or grape marc. In this contribution, the results of the first chemical characterization of a wide number of craft Filuferru samples has been accomplished in terms of evaluation of the alcoholic strength, qualitative and quantitative GC-MS analysis of the volatile composition of the distillate, and its trace element composition by means a ICP-MS method. Both instrumental methods have been validated and applied on 21 craft samples of Filuferru, whereas one sample of commercial distillate has been analyzed for comparison purposes. Alcoholic strength ranged between 41.0 and 62.4% (v/v). Sixty volatile compounds were identified and ten of them have been quantified. Analogies and differences with Grappa (i.e. the Italian distilled spirit most close to Filuferru) have been highlighted in the qualitative and quantitative profile of this matrix. Often meaningful amounts of acetalde...
Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last... more Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last decades, significant attention for its cultivation has risen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass contains also high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e. the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for Guayule shrub, in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins can possess significant biological properties (e.g, antibacterial and anticancer activities), in close analogy with those shown by sesq...
Enzyme-based sensors have emerged as important analytical tools with application in diverse field... more Enzyme-based sensors have emerged as important analytical tools with application in diverse fields, and biosensors for the detection of glucose using the enzyme glucose oxidase have been widely investigated. In this work, the preparation of biosensors by electrochemical polymerization of (poly)thiophenes, namely 2,2'-bithiophene (2,2'-BT) and 4,4'-bis(2-methyl-3-butyn-2-ol)-2,2'-bithiophene (4,4'-bBT), followed by immobilization of glucose oxidase on the films, is described. N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide metho--toluenesulfonate (CMC) was used as a condensing agent, and -benzoquinone (BQ) was used as a redox mediator in solution. The glucose oxidase electrodes with films of 2,2'-BT and 4,4'-bBT were then tested for their ability in detecting glucose from synthetic and real samples (pear, apricot, and peach fruit juices).
Fisetin (3,3',4',7-tetrahydroxyflavone) metal chelates are of interest as this plant poly... more Fisetin (3,3',4',7-tetrahydroxyflavone) metal chelates are of interest as this plant polyphenol has revealed broad prospects for its use as natural medicine in the treatment of various diseases. Metal interactions may change or enhance fisetin biological properties so understanding fisetin metal chelation is important for its application not only in medicine but also as a food additive in nutritional supplements. This work was aimed to determine and characterize copper complexes formed in different pH range at applying various metal/ligand ratios. Fisetin and Cu(II)-fisetin complexes were characterized by potentiometric titrations, UV-Vis (Ultraviolet-visible spectroscopy), EPR, ESI-MS, FTIR and cyclic voltammetry. Their effects on DNA were investigated by using circular dichroism, spectrofluorimetry and gel electrophoresis methods. The copper complex with the ratio of Cu(II)/fisetin 1/2 exhibited significant DNA cleavage activity, followed by complete degradation of DNA. Th...
Saccharides are functional constituents of milk. Although d-lactose represents almost the totalit... more Saccharides are functional constituents of milk. Although d-lactose represents almost the totality of the saccharides in the milk, minor species, like d-glucose, d-galactose, myo-inositol and, as a result of severe thermal treatments, monosaccharides like d-tagatose, are also detectable. Although chromatography has been the main analytical approach used for accomplishing this task, quite surprisingly a validated gas chromatographic method aimed at the simultaneous determination of these compounds is still needed. Hence, our contribution is devoted to fill this gap. After the optimization of clean-up and derivatization (conversion of saccharides in their trimethyl silyl ethers) steps, the adoption of a highly cross-linked silphenylene stationary phase permitted to obtain high resolution and a fast chromatographic run. Validation was accomplished in terms of limit of detection, limit of quantification, linearity, precision, and trueness. The accuracy of the method was successfully tested on a number of partially skimmed milk samples. Excellent limits of detection for all analytes make this method eligible, also with respect to a gas chromatographic/mass spectrometry approach, for routine analysis and quality control in the dairy industries.
Honey is one of the most renowned natural foods. Its composition is extremely variable, depending... more Honey is one of the most renowned natural foods. Its composition is extremely variable, depending on its botanical and geographical origins, and the abundant presence of functional compounds has contributed to the increased worldwide interest is this foodstuff. In particular, great attention has been paid by the scientific community towards classes of compounds like phenolic compounds, due to their capability to act as markers of unifloral honey origin. In this contribution the most recent progress in the assessment of new analytical procedures aimed at the definition of the qualitative and quantitative profile of phenolic compounds of honey have been highlighted. A special emphasis has been placed on the innovative aspects concerning the extraction procedures, along with the most recent strategies proposed for the analysis of phenolic compounds. Moreover, the centrality of validation procedures has been claimed and extensively discussed in order to ensure the fitness-for-purpose of the proposed analytical methods. In addition, the exploitation of the phenolic profile as a tool for the classification of the botanical and geographical origin has been described, pointing out the usefulness of chemometrics in the interpretation of data sets originating from the analysis of polyphenols. Finally, recent results in concerning the evaluation of the antioxidant properties of unifloral honeys and the development of new analytical approaches aimed at measuring this parameter have been reviewed.
The electrochemical properties of the liposoluble vitamin K1 adsorbed on bare and lipid coated gl... more The electrochemical properties of the liposoluble vitamin K1 adsorbed on bare and lipid coated glassy carbon electrodes (GCEs) were studied in unbuffered and well buffered aqueous media. The reduction products of vitamin K1 were characterized by employing cyclic voltammetry and the in situ UV-visible spectroelectrochemical technique. The radical species of vitamin K1 cannot be observed at the bare GCEs in well buffered media. The formation of the anion radical of vitamin K1 was observed in unbuffered solutions above pH 5.9 or at the lipid coated GCE in a well-buffered solution. UV-visible absorption bands of neutral vitamin K1 were observed at 260 nm and 330 nm, and a band corresponding to the anion radical species was observed at 450 nm. The derivative cyclic voltabsorptometric (DCVA) curves obtained for electrochemical reduction of vitamin K1 confirmed the presence of both neutral and anion radical species. The anion radical of vitamin K1 formed at the hydrophobic conditions with phosphatidylcholine (PC) lipid coated electrode was stable enough to be observed in the spectroelectrochemical experiments.
A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically poly... more A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically polymerized to give the corresponding metal-containing conducting polymer on gold and glassy carbon electrodes. The polymerization of the Ru(II) complex was allowed by a terthiophene functionalization on one of the two terpy coordinating fragments, whereas the presence of -COOH substituents on the second terpy ligand enabled the film to immobilize a tyrosinase enzyme by cross-linking with glutaraldehyde. Then, the Ru(terpy) conducting polymer worked as a transducer as well as an immobilizing agent in the design of amperometric biosensors for the determination of epinephrine. The electrochemical behavior of enzymatic sensors containing Ru(terpy)-based conducting polymers was investigated by differential pulse voltammetry and chronoamperometry. Analytical performances and kinetic parameters were calculated, suggesting a potential application of the reported biosensors in the determination of e...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The availability of fast and non-expensive analytical methods for the determination of widespread... more The availability of fast and non-expensive analytical methods for the determination of widespread interest analytes such as glucose is an object of large relevance; this is so not only in the field of analytical chemistry, but also in medicinal and in food chemistry. In this context, electrochemical biosensors have been proposed in different arrangements, according to the mode of electron transfer between the bioreceptor and the electrode. An efficient immobilization of an enzyme on the electrode surface is essential to assure satisfactory analytical performances of the biosensor in terms of sensitivity, limit of detection, selectivity, and linear range of employment. Here, we report the use of a thiophene monomer, (2,5-di(2-thienyl)thieno [3,2-b]thiophene (dTT-bT), as a precursor of an electrogenerated conducting film to immobilize the glucose oxidase (GOx) enzyme on Pt, glassy carbon (GC), and Au electrode surfaces. In addition, the polymer film electrochemically synthetized on a ...
Despite unifloral honeys from Sardinia, Italy, being appreciated worldwide for their peculiar org... more Despite unifloral honeys from Sardinia, Italy, being appreciated worldwide for their peculiar organoleptic features, their elemental signature has only partly been investigated. Hence, the principal aim of this study was to measure the concentration of trace and toxic elements (i.e., Ag, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Sn, Sr, Te, Tl, V, and Zn) in four unifloral honeys produced in Sardinia. For this purpose, an original ICP-MS method was developed, fully validated, and applied on unifloral honeys from asphodel, eucalyptus, strawberry tree, and thistle. Particular attention was paid to the method’s development: factorial design was applied for the optimization of the acid microwave digestion, whereas the instrumental parameters were tuned to minimize the polyatomic interferences. Most of the analytes’ concentration ranged between the relevant LoDs and few mg kg−1, while toxic elements were present in negligible amounts. The elemental signatures of asp...
We evaluate the influence of the use of different titania precursors, calcination rate, and ligan... more We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(O i Pr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and
5-(hydroxymethyl)furan-2-carbaldehyde, better known as hydroxymethylfurfural (HMF), is a well-kno... more 5-(hydroxymethyl)furan-2-carbaldehyde, better known as hydroxymethylfurfural (HMF), is a well-known freshness parameter of honey: although mostly absent in fresh samples, its concentration tends to increase naturally with aging. However, high quantities of HMF are also found in fresh but adulterated samples or honey subjected to thermal or photochemical stresses. In addition, HMF deserves further consideration due to its potential toxic effects on human health. The processes at the origin of HMF formation in honey and in other foods, containing saccharides and proteins—mainly non-enzymatic browning reactions—can also produce other furanic compounds. Among others, 2-furaldehyde (2F) and 2-furoic acid (2FA) are the most abundant in honey, but also their isomers (i.e., 3-furaldehyde, 3F, and 3-furoic acid, 3FA) have been found in it, although in small quantities. A preliminary characterization of HMF, 2F, 2FA, 3F, and 3FA by cyclic voltammetry (CV) led to hypothesizing the possibility ...
We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated ... more We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance but different electronic properties. As a result, the reactivity of the two series of complexes follows very different routes. In particular, the new complexes behave differently towards protonation reactions, differences given by substituents and ancillary ligands, added to the presence of several nucleophilic centers. Reaction of complex [Pt(bpy6OMe-H)(PPh3)Me)] with [H3O⋅18-crown-6][BF4] results in a retro-rollover reaction whose final product is the cationic adduct [Pt(bpy6OMe)(PPh3)Me)]+. Surprisingly, only the isomer with the cis-PPh3-OMe geometry is formed; in spite of an expected instability due to steric hindrance, Density-Functional theory (DFT...
Enzyme-based amperometric biosensors are proving to be important analytical tools in several fiel... more Enzyme-based amperometric biosensors are proving to be important analytical tools in several fields such as food, environmental and, in recent years, the biomedical one. This work describes the use of 4,7-bis(5-(pyridin-2-yl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TBT) in the development of a tyrosinase-based biosensor for epinephrine detection. The modifying agent was obtained as a film by electrochemical oxidation of TBT on a gold disk electrode. Electrochemical characterization and scanning electrode microscopy (SEM) images suggest the formation of a conducting film on the electrode surface. Tyrosinase from mushroom was then immobilized by a mixed technique of adsorption and cross-linking. Glutaraldehyde was used as a coupling agent. The obtained device shows a very good linear response (0.1-50 μM) with a LoD value of 0.06 μM and a LoQ of 0.09 μM. Moreover, good selectivity towards some typical interferents (namely, ascorbic acid, tryptophan, uric acid and L-cysteine) and satisfactory recoveries have been observed.
The lack of interest in the determination of toxic elements in liquids for electronic cigarettes ... more The lack of interest in the determination of toxic elements in liquids for electronic cigarettes (e-liquids) has so far been reflected in the scarce number of accurate and validated analytical methods devoted to this aim. Since the strong matrix effects observed for e-liquids constitute an exciting analytical challenge, the main goal of this study was to develop and validate an ICP-MS method aimed to quantify 23 elements in 37 e-liquids of different flavors. Great attention has been paid to the critical phases of sample pre-treatment, as well as to the optimization of the ICP-MS conditions for each element and of the quantification. All samples exhibited a very low amount of the elements under investigation. Indeed, the sum of their average concentration was of ca. 0.6 mg kg−1. Toxic elements were always below a few tens of a μg per kg−1 and, very often, their amount was below the relevant quantification limits. Tobacco and tonic flavors showed the highest and the lowest concentrati...
Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reactio... more Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C–H bond is regioselectively activated, affording an uncommon cyclometalated complex, called “rollover cyclometalated complex”. The key of the process is the internal rotation of the ligand, which occurs before the C–H bond activation and releases from coordination a donor atom. The new “rollover” ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C–H bond is usually in a symmetric positi...
The amount of specific trace elements like selenium (Se) may be of health concern for humans if c... more The amount of specific trace elements like selenium (Se) may be of health concern for humans if contained in too high (or low) quantities in staple foods like rice. Among the attempts aimed to optimize the Se concentration in rice, only few studies have been focused on the use of irrigation methods other than continuous flooding. Since intermittent irriguous methods, like sprinkler and saturation, have found to be effective in modifying the bioaccumulation of arsenic and cadmium in rice kernels, the main goal of this study is to measure the amount of the total Se contained in grains of 26 rice genotypes cultivated for two consecutive agrarian vintages in the same open field and with the same water, but differently irrigated with continuous flooding, sprinkler or saturation. To do this, an original and validated ICP-MS method has been developed. The validation parameters accounted for a high sensitivity and accuracy. Sprinkler irrigation is able to reduce in the average of 90% the am...
Structure-related biological activities of flavanones are still considered largely unexplored. Si... more Structure-related biological activities of flavanones are still considered largely unexplored. Since they exhibit various medicinal activities, it is intriguing to enter deeper into their chemical structures, electronic transitions or interactions with some biomolecules in order to find properties that allow us to better understand their effects. Little information is available on biological activity of flavanone and its monohydroxy derivatives in relation to their physicochemical properties as spectral profiles, existence of protonated/deprotonated species under pH changes or interaction with Calf Thymus DNA. We devoted this work to research demonstrating differences in the physicochemical properties of the four flavanones: flavanone, 2′-hydroxyflavanone, 6-hydroxyflavanone and 7-hydroxyflavanone and linking them to their biological activity. Potentiometric titration, UV–Vis spectroscopy were used to investigate influence of pH on acid–base and spectral profiles and to propose the ...
Traditional Filuferru is an ancient spirit from Sardinia, Italy, usually obtained from the distil... more Traditional Filuferru is an ancient spirit from Sardinia, Italy, usually obtained from the distillation of wine or grape marc. In this contribution, the results of the first chemical characterization of a wide number of craft Filuferru samples has been accomplished in terms of evaluation of the alcoholic strength, qualitative and quantitative GC-MS analysis of the volatile composition of the distillate, and its trace element composition by means a ICP-MS method. Both instrumental methods have been validated and applied on 21 craft samples of Filuferru, whereas one sample of commercial distillate has been analyzed for comparison purposes. Alcoholic strength ranged between 41.0 and 62.4% (v/v). Sixty volatile compounds were identified and ten of them have been quantified. Analogies and differences with Grappa (i.e. the Italian distilled spirit most close to Filuferru) have been highlighted in the qualitative and quantitative profile of this matrix. Often meaningful amounts of acetalde...
Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last... more Guayule (Parthenium argentatum Gray) is a shrub native of the arid regions of Mexico. In the last decades, significant attention for its cultivation has risen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass contains also high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e. the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for Guayule shrub, in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins can possess significant biological properties (e.g, antibacterial and anticancer activities), in close analogy with those shown by sesq...
Enzyme-based sensors have emerged as important analytical tools with application in diverse field... more Enzyme-based sensors have emerged as important analytical tools with application in diverse fields, and biosensors for the detection of glucose using the enzyme glucose oxidase have been widely investigated. In this work, the preparation of biosensors by electrochemical polymerization of (poly)thiophenes, namely 2,2'-bithiophene (2,2'-BT) and 4,4'-bis(2-methyl-3-butyn-2-ol)-2,2'-bithiophene (4,4'-bBT), followed by immobilization of glucose oxidase on the films, is described. N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide metho--toluenesulfonate (CMC) was used as a condensing agent, and -benzoquinone (BQ) was used as a redox mediator in solution. The glucose oxidase electrodes with films of 2,2'-BT and 4,4'-bBT were then tested for their ability in detecting glucose from synthetic and real samples (pear, apricot, and peach fruit juices).
Fisetin (3,3',4',7-tetrahydroxyflavone) metal chelates are of interest as this plant poly... more Fisetin (3,3',4',7-tetrahydroxyflavone) metal chelates are of interest as this plant polyphenol has revealed broad prospects for its use as natural medicine in the treatment of various diseases. Metal interactions may change or enhance fisetin biological properties so understanding fisetin metal chelation is important for its application not only in medicine but also as a food additive in nutritional supplements. This work was aimed to determine and characterize copper complexes formed in different pH range at applying various metal/ligand ratios. Fisetin and Cu(II)-fisetin complexes were characterized by potentiometric titrations, UV-Vis (Ultraviolet-visible spectroscopy), EPR, ESI-MS, FTIR and cyclic voltammetry. Their effects on DNA were investigated by using circular dichroism, spectrofluorimetry and gel electrophoresis methods. The copper complex with the ratio of Cu(II)/fisetin 1/2 exhibited significant DNA cleavage activity, followed by complete degradation of DNA. Th...
Saccharides are functional constituents of milk. Although d-lactose represents almost the totalit... more Saccharides are functional constituents of milk. Although d-lactose represents almost the totality of the saccharides in the milk, minor species, like d-glucose, d-galactose, myo-inositol and, as a result of severe thermal treatments, monosaccharides like d-tagatose, are also detectable. Although chromatography has been the main analytical approach used for accomplishing this task, quite surprisingly a validated gas chromatographic method aimed at the simultaneous determination of these compounds is still needed. Hence, our contribution is devoted to fill this gap. After the optimization of clean-up and derivatization (conversion of saccharides in their trimethyl silyl ethers) steps, the adoption of a highly cross-linked silphenylene stationary phase permitted to obtain high resolution and a fast chromatographic run. Validation was accomplished in terms of limit of detection, limit of quantification, linearity, precision, and trueness. The accuracy of the method was successfully tested on a number of partially skimmed milk samples. Excellent limits of detection for all analytes make this method eligible, also with respect to a gas chromatographic/mass spectrometry approach, for routine analysis and quality control in the dairy industries.
Honey is one of the most renowned natural foods. Its composition is extremely variable, depending... more Honey is one of the most renowned natural foods. Its composition is extremely variable, depending on its botanical and geographical origins, and the abundant presence of functional compounds has contributed to the increased worldwide interest is this foodstuff. In particular, great attention has been paid by the scientific community towards classes of compounds like phenolic compounds, due to their capability to act as markers of unifloral honey origin. In this contribution the most recent progress in the assessment of new analytical procedures aimed at the definition of the qualitative and quantitative profile of phenolic compounds of honey have been highlighted. A special emphasis has been placed on the innovative aspects concerning the extraction procedures, along with the most recent strategies proposed for the analysis of phenolic compounds. Moreover, the centrality of validation procedures has been claimed and extensively discussed in order to ensure the fitness-for-purpose of the proposed analytical methods. In addition, the exploitation of the phenolic profile as a tool for the classification of the botanical and geographical origin has been described, pointing out the usefulness of chemometrics in the interpretation of data sets originating from the analysis of polyphenols. Finally, recent results in concerning the evaluation of the antioxidant properties of unifloral honeys and the development of new analytical approaches aimed at measuring this parameter have been reviewed.
The electrochemical properties of the liposoluble vitamin K1 adsorbed on bare and lipid coated gl... more The electrochemical properties of the liposoluble vitamin K1 adsorbed on bare and lipid coated glassy carbon electrodes (GCEs) were studied in unbuffered and well buffered aqueous media. The reduction products of vitamin K1 were characterized by employing cyclic voltammetry and the in situ UV-visible spectroelectrochemical technique. The radical species of vitamin K1 cannot be observed at the bare GCEs in well buffered media. The formation of the anion radical of vitamin K1 was observed in unbuffered solutions above pH 5.9 or at the lipid coated GCE in a well-buffered solution. UV-visible absorption bands of neutral vitamin K1 were observed at 260 nm and 330 nm, and a band corresponding to the anion radical species was observed at 450 nm. The derivative cyclic voltabsorptometric (DCVA) curves obtained for electrochemical reduction of vitamin K1 confirmed the presence of both neutral and anion radical species. The anion radical of vitamin K1 formed at the hydrophobic conditions with phosphatidylcholine (PC) lipid coated electrode was stable enough to be observed in the spectroelectrochemical experiments.
A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically poly... more A heteroleptic [Ru(terpy)2]2+ (terpy = 2,2′:6′,2″-terpyridine) complex was electrochemically polymerized to give the corresponding metal-containing conducting polymer on gold and glassy carbon electrodes. The polymerization of the Ru(II) complex was allowed by a terthiophene functionalization on one of the two terpy coordinating fragments, whereas the presence of -COOH substituents on the second terpy ligand enabled the film to immobilize a tyrosinase enzyme by cross-linking with glutaraldehyde. Then, the Ru(terpy) conducting polymer worked as a transducer as well as an immobilizing agent in the design of amperometric biosensors for the determination of epinephrine. The electrochemical behavior of enzymatic sensors containing Ru(terpy)-based conducting polymers was investigated by differential pulse voltammetry and chronoamperometry. Analytical performances and kinetic parameters were calculated, suggesting a potential application of the reported biosensors in the determination of e...
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Papers by Maria Pilo