Luminescent determination of propineb fungicide by using a carbon quantum dots-europium ions system.

We propose a modification of lanthanide-sensitized luminescence (LSL) to increase the selectivity and sensitivity of analytical methods based on this detection. LSL consists in the formation of complexes of lanthanide ions and organic compounds. Then, an intramolecular energy transfer occurs from the excited state of the ligand (organic analyte) to the emitting level of the lanthanide. The utilization of luminescent nanoparticles (carbon quantum dots, CQDs) in LSL systems can enhance their sensitivity and selectivity. CQDs can react with lanthanide ions through their carboxylic groups. These systems can thus be used as time-resolved luminescent probes. Propineb (PPN), a well-known dithiocarbamate fungicide, has been selected as the target analyte to show the advantages of using CQDs in LSL systems. The method proposed is based on the quenching produced by PPN in europium-CQDs luminescence, obtaining a detection limit of 0.03 µg mL-1 PPN and a method detection limit of 3 mg kg-1 in capers (bud and fruit), fulfilling the maximum residue limit in these samples (25 mg kg-1). The results showed that the use of nanoparticles in LSL systems may provide novel and simple analytical methods for the screening of contaminants in the agri-food sector.

Sensitive fluorometric determination of quinclorac residues in rice.

Rice is one of the most important foods in the world due to its high nutritional value and production. Quinclorac, a selective herbicide, is one of the most detected pesticide residues in rice crops according to pesticide monitoring studies. Common methods for the determination of quinclorac in rice are very time-consuming and labour-intensive, so it is important to develop alternative sensitive and simple analytical methods able to detect quinclorac in food samples. Here we propose a fluorometric method for the screening of this herbicide at excitation/emission wavelengths of 238/358 nm/nm, respectively. A modified QuEChERS method was selected for sample treatment due to its simplicity and high recovery yields. The proposed method presents a detection limit of 2.5 ng mL-1 and satisfactory precision. Recovery experiments were performed in different kinds of rice (white and brown) at or below the Maximum Residue Limit established in European Union (5 mg kg-1), obtaining values close to 100%. All these characteristics ensure that the proposed method fulfils the requirements for its application in food control.

Comparative study of the phytochemical and mineral composition of fresh and cooked broccolini.

Broccolini is originated from crossing the regular broccoli with Chinese kale. Consequently, it has similar properties to these vegetables, but other very particular characteristics. Its consumption has increased in the last few years and, consequently, there have been some studies related to its quality parameters and the influence of different cooking methods. Nevertheless, changes on its phenolic composition and mineral content originated by its cooking have not been investigated in-depth so far. Here we report the phytochemical profile of broccolini before and after boiling, steaming, and griddling cooking treatments. The mineral content and phytochemicals were assessed by inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography-mass spectrometry (HPLC-MS), respectively. The main phenolics (mainly hydroxycinnamic acid derivatives from caffeic, coumaric, ferulic and sinapic acids) were quantified. Three oxylipins, three flavonoid glycosides and the glucosinolate glucobrassicin were also identified. ABTS and DPPH assays were also used as screening methods to assess the antioxidant potential of broccolini. A significant loss of the phenolic compounds and a reduction of the antioxidant activity were observed after the three cooking methods. Clear disadvantages were detected when broccolini was boiled, namely high losses of phenolic acids and derivatives (70%). Steaming and griddling also led to a significant loss of phenolics (50%) from fresh broccolini. The mineral content of this vegetable after domestic cooking procedures is also reported for the first time, calculating the contribution of broccolini consumption to official daily recommendations.

Automated on-line liquid-liquid extraction in a multisyringe flow injection analysis manifold for migration studies in food-contact materials: analysis of 4,4´-dihydroxybiphenyl.

Packaging may represent a source of food contamination, as different organic compounds and degradation compounds may migrate from packaging to foodstuff. For fatty foods, rectified olive oil is the common simulant, which implies time-consuming and laborious liquid-liquid extraction (LLE) procedures to isolate the contaminant(s) from the oil. Here we propose a Multisyringe Flow Injection Analysis manifold to automate this sample treatment, using the monomer 4,4´-dihydroxybiphenyl as the contaminant. The LLE procedure, using water as extractant, was fully automated. After the on-line LLE, the resulting extract was pumped through a fluorescence detector, inside which a flow-cell filled with C18 silica gel solid support was placed. The analyte was pre-concentrated on the solid support (in which the analytical signal was directly recorded), so improving the sensitivity of the system. Under optimum conditions, the method detection limit is 0.05 mg kg-1, well within the specific migration limit of 6 mg kg-1. The method developed was compared with the standard CEN test method (off-line LLE and HPLC determination) observing savings in sample and reagents of 90% and a 7-fold increase in sample throughput.

Graphene quantum dots-silver nanoparticles as a novel sensitive and selective luminescence probe for the detection of glyphosate in food samples.

Glyphosate (Gly) is the most widely used herbicide at the moment. It presents a broad spectrum of action, hence its use for many different crops. Regulatory agencies have constantly mentioned the low hazard potential of Gly to mammals. However, the International Agency for Research on Cancer concluded in 2015 that glyphosate is "probably carcinogenic to humans". For this reason, it is important to develop reliable analytical methods to quantify Gly in food samples. Here, we propose an analytical method that makes use of graphene quantum dots (GQDs) and cysteine-capped silver nanoparticles (AgNPs) for the screening of glyphosate, using QuEChERS as sample treatment. Gly quenched the luminescence of GQDs-AgNPs system, achieving an excellent sensitivity (detection limit of 9 ng mL-1) and selectivity. The method developed was applied to different types of pulses (peas and lupins), obtaining recoveries close to 100% and relative standard deviations lower than 4% in all cases. Its simplicity and rapidity make this method an interesting alternative to other existing methodologies for the analysis of this pesticide in food samples.

Automated Photochemically Induced Method for the Quantitation of the Neonicotinoid Thiacloprid in Lettuce.

In this work, we present an automated luminescence sensor for the quantitation of the insecticide thiacloprid, one of the main neonicotinoids, in lettuce samples. A simple and automated manifold was constructed, using multicommutated solenoid valves to handle all solutions. The analyte was online irradiated with UV light to produce a highly fluorescent photoproduct (λexc/λem = 305/370 nm/nm) that was then retained on a solid support placed in the flow cell. In this way, the pre-concentration of the photoproduct was achieved in the detection area, increasing the sensitivity of the analytical method. A method-detection limit of 0.24 mg kg-1 was achieved in real samples, fulfilling the Maximum Residue Limit (MRL) of The European Union for thiacloprid in lettuce (1 mg kg-1). A sample throughput of eight samples per hour was obtained. Recovery experiments were carried out at values close to the MRL, obtaining recovery yields close to 100% and relative standard deviations lower than 5%. Hence, this method would be suitable for routine analyses in quality control, as an alternative to other existing methods.

Multi-targeted potential of Pittosporum senacia Putt.: HPLC-ESI-MSn analysis, in silico docking, DNA protection, antimicrobial, enzyme inhibition, anti-cancer and apoptotic activity.

Pittosporum senacia (PS) Putt. (Pittosporaceae), indigenous to the Mascarene Islands, is a common ingredient in traditional medicines. However, there is currently a dearth of studies to validate some of these traditional claims. Given the broad traditional uses of PS against several diseases, we aimed to provide a comprehensive insight into the biological and chemical profile of P. senacia. The antioxidant, enzyme inhibitory activity, anticancer, and phytochemical composition of the methanolic extract of P. senacia leaf extracts were studied. The possible interaction and binding mode of the most abundant phytochemicals were studied via in silico docking experiments on tyrosinase and α-glucosidase. The mechanism behind the cytotoxic property of P. senacia extract for MDA-MB-231 was also examined using different methods including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability test checking apoptosis-associated genes, and wound healing assays. Twenty-six compounds were identified, of which caffeoylquinic acid derivatives, ferulic acid derivative, cinnamoylquinic acid derivative and two other polyphenols (oleuropeine and isoramnetin glucoside) being abundant, have been tested using in silico studies, against α-glucosidase and tyrosinase. The extract (IC50 = 118.8 µg/ml) exhibited time and dose dependent anti-proliferative effect on human breast cancer cell line, MDA-MB-231. According to the expression profile of apoptosis inhibitors and apoptosis promoters genes, expression of Bax and Bak genes were significantly increased compared to Bcl-2 and Birc5 genes. Based on wound healing analysis, cell migration was inhibited after the application of the plant extract. The present findings suggested that PS might be a good candidate as sources of bioactive compounds for designing functional applications.

Chemical profiling of Centaurea bornmuelleri Hausskn. aerial parts by HPLC-MS/MS and their pharmaceutical effects: From nature to novel perspectives.

Ethnobotanical evidences substantiate the use of several Centaurea species to treat and/or manage several human ailments. In the present study, the phytochemical profile of the ethyl acetate, methanol, and aqueous extracts (prepared by infusion and decoction) of Centaurea bornmuelleri Hausskn. aerial parts was established. The enzyme inhibitory and antioxidant properties were also determined by in vitro bioassays. Methanol extract (38.58 mg gallic acid equivalent/g extract) and ethyl acetate extract (38.83 mg rutin equivalent/g extract) possessed the highest concentration of phenolics and flavonoids, respectively. Aqueous extract prepared following traditional infusion method showed potent DPPH (38.54 mg TE/g extract) and ABTS (57.75 mg TE/g extract) scavenging abilities. The methanol extract (101.46 mg TE/g extract) of C. bornmuelleri exhibited potent reducing activity in the CUPRAC assay while the aqueous extract obtained by infusion was more active in the FRAP assay (69.81 mg TE/g extract). Ethyl acetate extract of C. bornmuelleri inhibited both acetylcholinesterase (1.14 mg galantamine equivalent [GALAE]/g extract), butyrylcholinesterase (0.63 mg GALAE/g extract), tyrosinase (69.84 mg kojic acid equivalent/g extract), amylase (19.90 mg acarbose equivalent [ACAE]/g extract), and glucosidase (33.12 mg ACAE/g extract). The phytochemical profile of C. bornmuelleri has been characterized and the main components quantified in order to provide scientific base to design innovative products including pharmaceuticals, cosmetics or nutraceuticals although further investigation concerning the isolation of the main bioactive compounds would be required.

Phytochemical profile, mineral content, and antioxidant activity of Olea europaea L. cv. Cornezuelo table olives. Influence of in vitro simulated gastrointestinal digestion.

The main goals of this study were to determine the phenolic composition and antioxidant activity of table olives from Olea europaea L. cv. Cornezuelo, as well as the effect caused by a simulated in vitro digestion to evaluate compounds bioavailability. High-performance liquid chromatography with diode-array and mass spectrometry detection (HPLC-DAD-MSn) was used to evaluate the phytochemical profile, whereas conventional spectrophotometric methods (ABTS·+ and DPPH) were used to determine the antioxidant activity. The mineral content was also quantified by inductively coupled plasma - mass spectrometry. Thirty compounds were identified, mainly polyphenols, quantifying the major compounds by HPLC-DAD. After the simulated digestion, the phenolic content suffered an important decrease - more than 50% - reaching losses of up to 75% for oleuropein and comselogoside isomers. This decrease also resulted in a loss of antioxidant activity, observing significant differences for all parameters. However, the analyzed extracts still retained considerable antioxidant potential.

Phenolic profile and antioxidant activity of Jasonia glutinosa herbal tea. Influence of simulated gastrointestinal in vitro digestion.

In order to value J. glutinosa DC (rock tea), we characterised its phenolic profile and antioxidant activity. The study was performed in aqueous extracts before and after a simulated in vitro digestion to obtain data regarding phenolics bioavailability. Methanolic extracts were also analysed for comparison purposes. Phytochemical profiles were determined by high-performance liquid chromatography with mass spectrometric detection, whereas total phenolic content (TPC) and antioxidant assays were performed by conventional spectrophotometric methods. The most abundant compounds were dicaffeoylquinic acids, representing more than 90% of phenolics in tea infusions. Statistically significant differences were observed for all parameters except for TPC in methanol and aqueous extracts. Both phenolics amount and antioxidant activities were lower after the in vitro digestion of the infusions. However, although phenolics were lost during the simulated digestion, rock tea is still a good source of bioactive compounds with potential applications in the pharmaceutical or nutraceutical industries.

Determination of thiacloprid, thiamethoxam and imidacloprid in tea samples by quenching terbium luminescence.

Consumption of herbal teas, infusions and other plant-related products has always been popular due to the related health benefits. However, the safety of these products needs to be assessed, for example monitoring the potential presence of contaminants such as pesticides. In this paper, we report an analytical method for determining three neonicotinoid insecticides - thiacloprid, thiamethoxam, and imidacloprid - that are widely used worldwide. This method is based on quenching by analytes of the luminescence signal of terbium ions. Terbium presents a time-resolved luminescence signal at 256/545 nm/nm, which is quenched by the presence of low concentrations of the selected analytes. Detection limits of 0.1, 0.2 or 0.75 µg ml-1 were obtained for thiamethoxam, thiacloprid and imidacloprid, respectively. Recovery experiments in different teas (green tea, black tea, chamomile, peppermint) were performed at concentrations lower than the maximum residue limits established by the European Union and the Codex Alimentarius for tea samples. In all cases, satisfactory recovery yields were observed, and the results were compared with a chromatographic reference method. The proposed method therefore proved suitable for quantifying these insecticides, fulfilling the current legislation.

Automated fluorimetric sensor for the determination of zearalenone mycotoxin in maize and cereals feedstuff.

Zearalenone (ZEA), a mycotoxin produced by several Fusarium molds, can be found in many cereals and related products. The toxicity of ZEA has been reported for both humans and animals. Therefore, many countries have adopted regulations in foods and feed materials to limit the exposure to this contaminant. In this paper, we propose a multicommutated flow-through optosensor to quantify ZEA in different cereal samples. ZEA was retained and pre-concentrated on C18 silica gel, and the use of the multicommutated flow manifold allowed the automated retention/desorption of ZEA on the solid microbeads by the use of appropriate carrier/eluting solutions, hence increasing the selectivity and sensitivity of the system. The native fluorescence of ZEA was recorded on the solid phase at λexc/λem of 265/465 nm/nm. A QuEChERS procedure was used to carry out the extraction of ZEA from different cereal samples (feedstuff materials). Recovery studies were performed to assess the accuracy of the method, obtaining recovery yields between 93% and 107% in all the analyzed samples. LC-MS was employed as reference method. The quantitation limit of the proposed method was low enough to fulfill the maximum residue levels established by the Commission of the European Communities, thus demonstrating its potential use for the analysis of ZEA in feedstuffs.

Phytochemical profile and antioxidant activity of caper berries (Capparis spinosa L.): Evaluation of the influence of the fermentation process.

In this work, we report the phytochemical profile and antioxidant activity of caper berries (Capparis spinosa L.) before and after a fermentation process. The phytochemical profiles were evaluated by high-performance liquid chromatography with UV and electrospray ionization mass spectrometry detection (HPLC-DAD-ESI-MSn). Twenty-one compounds were characterized, and seven of them quantified. The main component of non-fermented berries was glucocapparin, which was degraded upon the fermentation process. Most of the compounds were quercetin and kaempferol glycosides, epicatechin, and proanthocyanidins. The main differences observed upon the fermentation process were a decrease in epicatechin concentration, the hydrolysis of quercetin glycosides, and the degradation of glucosinolates. Total phenolic and flavonoid contents, as well as the antioxidant activities by the in vitro antioxidant assays DPPH and ABTS+, were determined, observing that the values were slightly higher after the fermentation process.

Evaluation of antioxidant potential, enzyme inhibition activity and phenolic profile of Lathyrus cicera and Lathyrus digitatus: Potential sources of bioactive compounds for the food industry.

The genus Lathyrus has great importance in terms of food and agricultural areas. In this study, the in vitro antioxidant activity (phosphomolybdenum, DPPH, ABTS, FRAP, CUPRAC and metal chelating) and enzyme inhibitory activity evaluation (acetylcholinesterase, butyrylcholinesterase, α-amylase and α-glucosidase) of L. cicera and L. digitatus were investigated, as well as their phytochemical profiles. The screening of the main phytochemical compounds in aerial parts of L. cicera and L. digitatus was carried out by high-performance liquid chromatography with electrospray ionization mass spectrometric detection (HPLC-ESI-MSn), observing that flavonoids represent the highest percentage of identified compounds, with abundance of tri- and tetra-glycosilated flavonoids, including acylated ones, especially in L. cicera. Generally, L. digitatus exhibited stronger antioxidant and enzyme inhibitory activities in correlation with its higher level of phenolics. The high number of phenolic compounds and the results of the antioxidant and enzyme assays suggest that these plants may be further used as sources of bioactive compounds, and for the preparation of new nutraceuticals.

Multi-commutated fluorometric optosensor for the determination of citrinin in rice and red yeast rice supplements.

Citrinin is a toxic secondary metabolite first isolated from Penicillium citrinum, although is also produced by other species of Penicillium and Aspergillus. It has highly toxic, mutagenic, teratogenic and carcinogenic properties and is often found in crops, vegetables and fruit. To our knowledge there is no specific legislation on maximum levels permitted for citrinin, so no official analytical method is currently available for its determination. Our laboratory developed a fluorometric flow-through optosensor using Sephadex SPC-25 as solid support. Multi-commutated flow injection analysis was used for the construction of the manifold and for handling solutions. In this way, we minimised waste generation and human intervention, which are critical aspects when dealing with highly toxic compounds such as citrinin. The optimum excitation/emission wavelengths were set at 330/494 nm; the calibration curve was linear in the concentration range 35-900 ng ml⁻¹. A detection limit of 10.5 ng ml⁻¹ and relative standard deviations (RSDs) lower than 3% were obtained. The developed optosensor was applied to the determination of citrinin in rice and dietary supplements containing red yeast rice.

Separation of a binary mixture of pesticides in fruits using a flow-through optosensor.

A flow-through optosensor is here proposed for the determination of mixtures of two widely used pesticides, carbendazim and o-phenylphenol, in fruits. The pesticides are separated on-line using an additional amount of solid support, C18 silica gel, in the flow-through cell. The resolution is performed due to the different retention/desorption kinetics of the analytes when interacting with the C18 microbeads. Therefore, both separation and determination are integrated in the same cell, considerably simplifying the system. In addition, the use of Sequential Injection Analysis provides a high degree of automation and minimum wastes generation. After the analytes are separated, their native fluorescence is measured, obtaining linearity in the 2.0-30 and 1.1-20 mg kg(-1) ranges for carbendazim and o-phenylphenol. The detection limits are 0.60 and 0.33 mg kg(-1) for carbendazim and o-phenylphenol respectively. The proposed method fulfills the maximum residue limits (MRLs) established in Europe and USA for these pesticides in cherries, pineapple, and mango: 5-10 mg kg(-1). In order to demonstrate the suitability of the method, several samples have been analyzed and the obtained results compared with a chromatographic method.

A novel multi-commutated method for the determination of hydroxytyrosol in enriched foods using mercaptopropionic acid-capped CdTe quantum dots.

Hydroxytyrosol (HXT) has been reported to have beneficial effects for human health, such as antioxidant and antimicrobial properties and an important contribution to the prevention of cardiovascular disease. Hence, exhaustive research is currently being performed to prepare functional foods, such as tomato juice or milk, with HXT. This paper presents a multi-commutated flow method based on the quenching effect that HXT has on the fluorescence of water-soluble mercaptopropionic acid-capped CdTe quantum dots. Under optimal conditions a linear working range was obtained for concentrations between 10 and 250 ng µl⁻¹. In order to demonstrate the suitability of the proposed method for the determination of HXT, HXT-enriched samples were prepared. Using a QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure for extraction, HXT was determined in the prepared functional foods (milk, infant formula, tomato juice and tomato soup). Recoveries of 100% ± 8%, relative standard deviations (RSDs) lower than 5% and high sample throughput of 70 samples per h show the potential of the system for the analysis of HXT in food samples.

Application of quantum dots in clinical and alimentary fields using multicommutated flow injection analysis.

In recent years, the number of scientific papers regarding the use of quantum dots (QDs) has increased almost exponentially, especially emphasizing their use for new applications and describing new approaches. One of the future trends in the development of new methods of analysis is the use of automated methodologies. Among them, Multicommutated Flow Injection Analysis has been here selected in order to show its potentiality in pharmaceutical and food analysis. Using water-soluble CdTe QDs modified by mercaptopropionic acid, a flow system was developed for the determination of ascorbic acid. The system was based on the quenching effect produced by ascorbic acid on the fluorescence of QDs. Under the optimized conditions, the relationship between the fluorescence intensity of the QDs and ascorbic acid concentration was linear in the range of 12-250 µg mL(-1), obtaining a sample throughput of 68 determinations per hour. The proposed method was applied to the determination of ascorbic acid in pharmaceutical formulations, goji capsules and fruit juices. The results obtained were in good agreement with those showed by a reference method, so indicating the utility of the proposed method in the clinical and alimentary fields.

Study of the quenching effect of quinolones over CdTe-quantum dots using sequential injection analysis and multicommutation.

The field of light-emitting nanoparticles has experienced an enormous development over the past two decades. The fluorescence of these nanometer-size crystalline particles, called quantum dots (QDs), can be both quenched and enhanced by different compounds. Since a high percentage of articles related to QDs are focused on theoretical studies, the development of analytical methods with real applications is an important step in order to progressively demonstrate the versatility of these particles. Moreover, taking into account that most of the QDs-based analytical methods are non-automated, the development of automated flow methodologies is still a field that presents an important analytical potential. With this purpose, two automatic methodologies, multicommutated flow injection analysis and sequential injection analysis, have been here applied to the analysis of quinolones in pharmaceutical formulations, making use of the quenching effect caused by the analytes over mercaptopropionic acid-capped CdTe QDs fluorescence. Both methodologies were compared in terms of versatility, sample throughput, sensitivity, etc., and applied to the determination of five quinolones in pharmaceutical preparations available in the Spanish Pharmacopoeia. The detection limits ranged between 26 and 50µmolL(-1), and Relative Standard Deviations lower than 3% were observed in all cases.

Fluorimetric determination of thiabendazole residues in mushrooms using sequential injection analysis.

Thiabendazole is a benzimidazole fungicide of general use that is specifically used to control mushroom diseases, mainly cobweb diseases, which is caused by members of the genus Cladobotryum. Although this compound is legislated and its maximum residue limit established at 60mgkg(-1) by Codex Alimentarius, there is almost a complete absence of analytical methods available for its determination in mushrooms. Here, we propose an automated method, using Sequential Injection Analysis with fluorescence detection (λ(exc)/λ(em)=305/345nm) for the determination of thiabendazole in mushrooms. We have developed a flow-through optosensor using C(18) silica gel as solid support placed in the flow-cell where the determination is performed. This method presents a detection limit of 0.5mgkg(-1), and recovery experiments have been carried out in different kinds of mushrooms at levels below the legislated maximum residue limit, demonstrating that the proposed analytical method fulfils the requirements for its applications in quality control of mushrooms.