Differences and similarities in selenium biopathways in Astragalus, Neptunia (Fabaceae) and Stanleya (Brassicaceae) hyperaccumulators.

BACKGROUND AND AIMS: Selenium hyperaccumulator species are of primary interest for studying the evolution of hyperaccumulation and for use in biofortification because selenium is an essential element in human nutrition. In this study, we aimed to determine whether the distributions of selenium in the three most studied hyperaccumulating taxa (Astragalus bisulcatus, Stanleya pinnata and Neptunia amplexicaulis) are similar or contrasting, in order to infer the underlying physiological mechanisms. METHODS: This study used synchrotron-based micro-X-ray fluorescence (µXRF) techniques to visualize the distribution of selenium and other elements in fresh hydrated plant tissues of A. racemosus, S. pinnata and N. amplexicaulis. KEY RESULTS: Selenium distribution differed widely in the three species: in the leaves of A. racemosus and N. amplexicaulis selenium was mainly concentrated in the pulvini, whereas in S. pinnata it was primarilylocalized in the leaf margins. In the roots and stems of all three species, selenium was absent in xylem cells, whereas it was particularly concentrated in the pith rays of S. pinnata and in the phloem cells of A. racemosus and N. amplexicaulis. CONCLUSIONS: This study shows that Astragalus, Stanleya and Neptunia have different selenium-handling physiologies, with different mechanisms for translocation and storage of excess selenium. Important dissimilarities among the three analysed species suggest that selenium hyperaccumulation has probably evolved multiple times over under similar environmental pressures in the US and Australia.

The Design of Experiment as a Tool to Model Plant Trace-Metal Bioindication Abilities.

Bioindicator plants are species that have the capacity to linearly uptake some elements (metal and metalloids) from the growing substrate, thus reflecting their concentration in the soil. Many factors can influence the uptake of these elements by plants, among which is the simultaneous presence of several metals, a common situation in contaminated or natural soils. A novel approach that can be used to validate the bioindication ability of a species growing on a polymetallic substrate is the design of experiment (DoE) approach. The aim of the present study was to apply the DoE in full factorial mode to model the Cu, Cd, Pb, Zn, and Cr bioindication capacity of Polygonum aviculare, used as the model plant. The results showed that P. aviculare has the ability to bioindicate Cd and Cr with a linear uptake (from 0.35 to 6.66, and 0.1 to 3.4 mg kg-1, respectively) unaffected by the presence of other metals. Conversely, the uptake of Pb, Cu, and Zn is strongly influenced by the presence of all the studied metals, making their concentration in the plant shoot not proportional to that of the soil. In conclusion, these preliminary results confirmed that the DoE can be used to predict the bioindicator abilities of a plant for several elements at the same time and to evaluate the interactions that can be established between variables in the growing medium and in the plant itself. However, more studies including other plant species are needed to confirm the effectiveness of this method.

Production of Antioxidant Molecules in Polygonum aviculare (L.) and Senecio vulgaris (L.) under Metal Stress: A Possible Tool in the Evaluation of Plant Metal Tolerance.

Plants growing on heavy metal (HM)-polluted soils show toxicity symptoms, such as chlorosis and growth reduction, and undergo oxidative stress due to the formation of reactive oxygen species (ROS). Plants overcome oxidative stress by producing a wide range of antioxidant molecules, such as polyphenols and flavonoids. The aim of the present work was to study the accumulation of these molecules in response to increasing concentrations of Cd, Cr, Cu, Ni, Pb and Zn and to assess whether they can be used as a tool in assessing metal-related stress in Polygonum aviculare and Senecio vulgaris. On average, P. aviculare shoots accumulated lower amounts of metals than S. vulgaris shoots. The uptake of all six elements was correlated and proportional to their concentration in the nutrient solution (ρ > 0.9), with the bioaccumulation factor (BAF) being >1 for most of them. The present research demonstrated that 82% of the samples showed a good correlation (|ρ| > 0.5) between the level of polyphenols, flavonoids and antioxidant activity and the metal concentration in plant shoots, confirming that the metal stress level and production of phenolic compounds having antioxidant activity were strictly connected. Nonetheless, the mere quantification of these molecules cannot identify the type of metal that caused the oxidative stress, neither determine the concentration of the stressors. The five tested populations of each species did not show any specific adaptation to the environment of origin.

State-of-the-Art Production Chains for Peas, Beans and Chickpeas-Valorization of Agro-Industrial Residues and Applications of Derived Extracts.

The world is confronted with the depletion of natural resources due to their unsustainable use and the increasing size of populations. In this context, the efficient use of by-products, residues and wastes generated from agro-industrial and food processing opens the perspective for a wide range of benefits. In particular, legume residues are produced yearly in very large amounts and may represent an interesting source of plant proteins that contribute to satisfying the steadily increasing global protein demand. Innovative biorefinery extraction cascades may also enable the recovery of further bioactive molecules and fibers from these insufficiently tapped biomass streams. This review article gives a summary of the potential for the valorization of legume residual streams resulting from agro-industrial processing and more particularly for pea, green bean and chickpea by-products/wastes. Valuable information on the annual production volumes, geographical origin and state-of-the-art technologies for the extraction of proteins, fibers and other bioactive molecules from this source of biomass, is exhaustively listed and discussed. Finally, promising applications, already using the recovered fractions from pea, bean and chickpea residues for the formulation of feed, food, cosmetic and packaging products, are listed and discussed.

Prêt-à-porter nanoYESα and nanoYESß bioluminescent cell biosensors for ultrarapid and sensitive screening of endocrine-disrupting chemicals.

Cell-based assays utilizing reporter gene technology have been widely exploited for biosensing, as they provide useful information about the bioavailability and cell toxicity of target analytes. The long assay time due to gene transcription and translation is one of the main drawbacks of cell biosensors. We report the development of two yeast biosensors stably expressing human estrogen receptors α and ß and employing NanoLuc as the reporter protein to upgrade the widely used yeast estrogen screening (YES) assays. A viability control strain was also developed based on a chimeric green-emitting luciferase, PLG2, expressed for the first time in Saccharomycescerevisiae. Thanks to their brightness, NanoLuc and PLG2 provided excellent sensitivity, enabling the implementation of these biosensors into low-cost smartphone-based devices. The developed biosensors had a rapid (1 h) response and reported on (anti)estrogenic activity via human estrogen receptors α and ß as well as general sample toxicity. Under optimized conditions, we obtained LODs of 7.1 ± 0.4 nM and 0.38 ± 0.08 nM for E2 with nanoYESα and nanoYESß, respectively. As a proof of concept, we analyzed real samples from plants showing significant estrogenic activity or known to contain significant amounts of phytoestrogens. Graphical abstract.

Heavy Metals Bioindication Potential of the Common Weeds Senecio vulgaris L., Polygonum aviculare L. and Poa annua L.

In recent years, heavy metals (HMs) levels in soil and vegetation have increased considerably due to traffic pollution. These pollutants can be taken up from the soil through the root system. The ability of plants to accumulate HMs into their tissues can therefore be used to monitor soil pollution. The aim of this study was to test the ruderal species Senecio vulgaris L., Polygonum aviculare L., and Poa annua L., as possible candidates for biomonitoring Cu, Zn, Cd, Cr, Ni and Pb in multiple environments. The soils analyzed in this work came from three different environments (urban, woodland, and ultramafic), and therefore deeply differed for their metal content, texture, pH, and organic matter (OM) content. All urban soils were characterized by high OM content and presence of anthropogenic metals like Pb, Zn, Cd, and Cu. Woodland soils were sandy and characterized by low metal content and low OM content, and ultramafic soils had high Ni and Cr content. This soil variability affected the bioindication properties of the three studied species, leading to the exclusion of most metals (Zn, Cu, Cr, Cd, and Pb) and one species (P. aviculare) due to the lack of linear relations between metal in soil and metal in plants. Senecio vulgaris and Poa annua, conversely, appeared to be good indicators of Ni in all the soils tested. A high linear correlation between total Ni in soil and Ni concentration in P. annua shoots (R2 = 0.78) was found and similar results were achieved for S. vulgaris (R2 = 0.88).

Exploiting NanoLuc luciferase for smartphone-based bioluminescence cell biosensor for (anti)-inflammatory activity and toxicity.

The availability of smartphones with high-performance digital image sensors and processing power has completely reshaped the landscape of point-of-need analysis. Thanks to the high maturity level of reporter gene technology and the availability of several bioluminescent proteins with improved features, we were able to develop a bioluminescence smartphone-based biosensing platform exploiting the highly sensitive NanoLuc luciferase as reporter. A 3D-printed smartphone-integrated cell biosensor based on genetically engineered Hek293T cells was developed. Quantitative assessment of (anti)-inflammatory activity and toxicity of liquid samples was performed with a simple and rapid add-and-measure procedure. White grape pomace extracts, known to contain several bioactive compounds, were analyzed, confirming the suitability of the smartphone biosensing platform for analysis of untreated complex biological matrices. Such approach could meet the needs of small medium enterprises lacking fully equipped laboratories for first-level safety tests and rapid screening of new bioactive products. Graphical abstract Smartphone-based bioluminescence cell biosensor.

Effects of chitosan on the protein profile of grape cell culture subcellular fractions.

Grapevine is a large source of healthy polyphenols for human diet, and red table-grapes and wines are the main source of stilbenes. These compounds are important both in the plant defence system and for human health. In the present study, Vitis vinifera cv. Barbera cell cultures were treated with 50 µg/mL chitosan and proteomic analyses on soluble and membrane subcellular fractions were performed against suitable controls. Three soluble stilbene synthase protein spots, four stilbene synthase spots in the microsomal fraction and four spots of membrane ATPase subunits were identified, the accumulation of which was modulated in response to chitosan treatment. Present proteomic and immunolocalisation data seem to provide evidence supporting the hypothesis that a stilbene biosynthetic multi-enzyme complex is associated with the intracellular membrane. In addition, proteomic analyses showed a general decrease in the accumulation of proteins belonging to different primary metabolism pathways, both in the soluble and membrane fractions. In particular, energy, sugar and amino acid metabolisms were down-regulated as a consequence of chitosan and acetic acid treatments. These metabolic modifications could lead to a consistent change in the profile and amount of metabolites stored in grape berries, with consequent effects on taste, flavour, organoleptic and nutraceutical properties of derived food products.

New Insights on Primary and Secondary Metabolite Contents of Seven Italian Wild Food Plants with Medicinal Applications: A Comparative Study.

Wild food plants are widely consumed all over the world and many have both nutritional and therapeutic value due to the presence of biologically active compounds. The present research, for the first time, aims to compare primary and secondary metabolite levels among different plant organs (flower, leaf, stem, root, bark) of seven species (Borago officinalis L., Cynodon dactylon (L.) Pers., Foeniculum vulgare Mill., Hypericum perforatum L., Malva sylvestris L., Sambucus nigra L., Urtica dioica L.) collected in three different Italian regions (Liguria, Tuscany, Apulia). Plant organ samples were extracted with water or 95% (v/v) methanol and liquid fractions were analyzed using spectrophotometric assays. The best results were obtained for Hypericum perforatum L. samples, followed by Sambucus nigra L. and Borago officinalis L. As also confirmed via PCA analysis on normalized data, flower and leaf extracts of all species exhibited higher levels of polyphenols (up to 105.7 mg GA eq/gDW), reducing sugars (up to 389.2 mg GLUC eq/gDW), proteins (up to 675.7 mg BSA eq/gDW) and of antioxidant capacity (up to 263.5 mg AA eq/gDW). No differences among the regions of gathering were detected after spectrophotometric assays, which was confirmed via PCA analysis. These data contribute to further validate the traditionally reported healing effects of these species on human health.

Foraging for selenium: a comparison between hyperaccumulator and non-accumulator plant species.

Selenium (Se) hyperaccumulators are a unique group of plants that can accumulate this element in their aerial parts at concentrations exceeding 100 mg kgDW-1. These plants actively search for Se in the soil, a phenomenon known as root foraging, reported to date only by few studies. In this study, the effect of localized Se enrichment, in the form of selenite and selenate, was investigated on the root architecture of two Se-hyperaccumulators (Stanleya pinnata and Astragalus bisulcatus) and two non-accumulators (Brassica juncea and Medicago sativa). Rhizoboxes were divided into two halves: one half was filled with control soil while the other with selenate or selenite (30 mg kgDW-1) spiked soil. Seedling were transferred into the interface of the two soils and allowed to grow for three weeks under controlled light and temperature conditions. Staneya pinnata exhibited equal root density in both halves of the rhizobox when grown in control/control and selenite/control soil treatments. However, in the presence of selenate, S. pinnata developed 76% of the roots towards the selenate-enriched half, indicating an active root foraging. In contrast, A. bisulcatus and the non-accumulators B. juncea and M. sativa did not show any preferential distribution of roots. This study revealed that only S. pinnata showed the ability to detect and forage for Se when provided as selenate. Non-accumulators did not show any morphological or Se-accumulation difference associated with the presence of Se in soil in either form.

Antioxidant and Sensory Properties of Raw and Cooked Pork Meat Burgers Formulated with Extract from Non-Compliant Green Coffee Beans.

The effects of polyphenol-rich extract obtained from non-compliant defatted green coffee beans (dGCBs) on physicochemical and antioxidant properties, as well as on the sensory profile of vacuum-packed pork burgers stored at 4 °C for 14 days and after cooking were assessed. The dGCB extract obtained by means of supercritical water extraction was analyzed for its polyphenol profile, total phenolic content, radical scavenging, and ferric-reducing antioxidant activities (DPPH and FRAP), Fe2+-chelating capacity, and total iron. The most abundant polyphenol component observed in the dGCB extract was chlorogenic acid, and the alkaloid caffeine was also present. This extract showed antioxidant properties. Thereafter, five formulations of pork meat burgers with added NaCl (1%) were prepared; one without the antioxidant (negative control, C) and one with the use of a synthetic antioxidant (0.05% ascorbic acid = positive control, A), while the other three were supplemented with a different amount of dGCB extract (P15 = 0.15%; P30 = 0.30%; P60 = 0.60%). The addition of dGCB extract increased the antioxidant activity of the raw and cooked burgers and reduced the lipid oxidation of the cooked burgers (0.47, 0.21, and 0.20 vs. 1.28 and 0.55 mg MDA eq./Kg, for P15, P30, and P60 vs. C and A, respectively). No negative effects were observed on the meat's color parameters and its stability during refrigerated storage and after cooking, nor on sensory attributes (color and aroma) for the lowest concentration of coffee extract. The results obtained indicate that 0.15% dGCB extract is a promising alternative to commercial synthetic antioxidants to improve the quality of refrigerated pork burgers.

Phytochemicals Recovery from Grape Pomace: Extraction Improvement and Chemometric Study.

In the last 20 years, an increased interest has been shown in the application of different types and combinations of enzymes to obtain phenolic extracts from grape pomace in order to maximize its valorization. Within this framework, the present study aims at improving the recovery of phenolic compounds from Merlot and Garganega pomace and at contributing to the scientific background of enzyme-assisted extraction. Five commercial cellulolytic enzymes were tested in different conditions. Phenolic compound extraction yields were analyzed via a Design of Experiments (DoE) methodology and a second extraction step with acetone was sequentially added. According to DoE, 2% w/w enzyme/substrate ratio was more effective than 1%, allowing a higher total phenol recovery, while the effect of incubation time (2 or 4 h) variation was more enzyme-dependent. Extracts were characterized via spectrophotometric and HPLC-DAD analyses. The results proved that enzymatic and acetone Merlot and Garganega pomace extracts were complex mixtures of compounds. The use of different cellulolytic enzymes led to different extract compositions, as demonstrated using PCA models. The enzyme effects were observed both in water enzymatic and in the subsequent acetone extracts, probably due to their specific grape cell wall degradation and leading to the recovery of different molecule arrays.

Ethnobotanical Review and Dataset Compiling on Wild and Cultivated Plants Traditionally Used as Medicinal Remedies in Italy.

Over the centuries, wild plants have constituted the main food ingredients and traditional medicine in rural communities. In the last decades, thousands of ethnobotanical studies have been conducted, with the aim of documenting the traditional knowledge on wild and cultivated plants both for food and therapeutic purposes. In the present work, 75 published papers related to Italian ethnobotanical knowledge on wild and cultivated plants traditionally used for medical purposes were analyzed and data on 1117 different species organized in the first dataset to target medicinal applications only. For each plant species, the Italian region of use, plant organs, mode of preparation, specific pathological group of application, citation index, and use index were listed. The different therapeutic applications were subdivided into nine main pathological groups according to the targeted human apparatus. Overall, the cited species with highest number of uses were related to the treatment of the digestive system and skin-ears-eyes-hair diseases, followed by diseases of the genito-urinary and respiratory systems. The 13 most relevant species were identified on the basis of their citation and use indexes. The present review on Italian medicinal flora aims to provide valuable information on wild and cultivated species, which are potential sources of plant-based therapeutic remedies, to preserve and reevaluate endangered traditional folk knowledge.

Looking for peptides from rice starch processing by-product: Bioreactor production, anti-tyrosinase and anti-inflammatory activity, and in silico putative taste assessment.

One of the major challenges for the modern society, is the development of a sustainable economy also aiming at the valorization of agro-industrial by-products in conjunction with at a significant reduction of generated residues from farm to retail. In this context, the present study demonstrates a biotechnological approach to yield bioactive peptides from a protein fraction obtained as a by-product of the rice starch production. Enzymatic hydrolysis, with the commercial proteases Alcalase and Protamex, were optimized in bioreactor up to 2 L of volume. The two best digestates, selected with respect to peptide release and extract antioxidant capacity, were further fractionated (cut-offs of 10, 5, and 1 kDa) via cross-flow filtration. Amino acid composition indicated that most of the fractions showed positive nutritional characteristics, but a putative bitter taste. A fraction obtained with Alcalase enzyme (retentate 8 kDa) exerted anti-inflammatory potential, while the smaller molecular weight fractions (retentate 1-5 kDa and permeate < 1 kDa) were more active in tyrosinase inhibition. The latter were further sub-fractionated by size-exclusion chromatography. From the 15 most anti-tyrosinase sub-fractions, 365 peptide sequences were identified via liquid chromatography coupled with high resolution mass spectrometry. The present data support the possible exploitation of bioactive peptide from rice starch by-product as ingredients into food, nutraceutical, pharmaceutical, and cosmetic formulations.

Induction of hormesis in plants by urban trace metal pollution.

Hormesis is a dose-response phenomenon observed in numerous living organisms, caused by low levels of a large number of stressors, among which metal ions. In cities, metal levels are usually below toxicity limits for most plant species, however, it is of primary importance to understand whether urban metal pollution can threaten plant survival, or, conversely, be beneficial by triggering hormesis. The effects of Cd, Cr and Pb urban concentrations were tested in hydroponics on three annual plants, Cardamine hirsuta L., Poa annua L. and Stellaria media (L.) Vill., commonly growing in cities. Results highlighted for the first time that average urban trace metal concentrations do not hinder plant growth but cause instead hormesis, leading to a considerable increase in plant performance (e.g., two to five-fold higher shoot biomass with Cd and Cr). The present findings, show that city habitats are more suitable for plants than previously assumed, and that what is generally considered to be detrimental to plants, such as trace metals, could instead be exactly the plus factor allowing urban plants to thrive.

Phytochemical characterization of raw and cooked traditionally consumed alimurgic plants.

In the past, wild edible alimurgic plants became an important alternative food source when poverty, wars or drought made it difficult to access crops. These plants were considered rich in highly nutritional compounds and also frequently used as food-medicine given their health-promoting properties. With the aim of improving our knowledge on the content of beneficial or detrimental compounds in relation with past local dietary and curative traditions, 12 wild food plant species were collected from two study areas selected for their very different degree of industrialization, urbanization, and conservation of local past traditions among the population: the Bologna province (Northern Italy) and the Middle Agri Valley (Southern Italy). Protein, polyphenol flavonoid and biogenic amine (both free and conjugated) contents and antioxidant activity of raw and boiled wild food plant extracts, and of cooking water were analyzed by means of spectrophotometric and high-performance liquid chromatography methods. The results demonstrated that most of the phenolic compounds were released in the cooking water which also showed the highest antioxidant activity. Seventeen different phenolic compounds were identified, of which the health-related luteolin, luteolin-7-glucoside and rutin were the most abundant (e.g., S. pratensis L. and C. intybus L.). On the other hand, biogenic amines were absent or present at very low levels in cooking water of those very same species (e.g., S. pratensis L., T. officinalis Weber, C. vesicaria subsp. taraxacifolia and C. intybus L.) of which traditionally a decoction is used for therapeutic purposes. Free and conjugated spermidine and spermine were generally the most abundant biogenic amines, while none of the known detrimental monoamines (e.g., histamine) was detected. In conclusion, the present results seem to support past local popular traditions which indicated beneficial medical properties of some wild edible plant, as well as of their cooking water.

Orthogonal paper biosensor for mercury(II) combining bioluminescence and colorimetric smartphone detection.

Mercury contamination in the environment has reached alarming levels. Due to its persistence and bioaccumulation, mercury is one of the most widespread toxic heavy metals found in air, water and food. Thus, it is mandatory to monitor mercury and its compounds, and the availability of sensitive and rapid biosensors is highly valuable. We developed a low-cost biosensor for orthogonal detection of mercury(II) integrating three different biorecognition principles on a three-leaf paper: i) a mercury-specific bioluminescent Escherichia coli bioreporter strain expressing NanoLuc luciferase as reporter protein, ii) a purified ß-galactosidase (ß-gal) enzyme which is irreversibly inhibited by mercury and other metal ions, and iii) an Aliivibrio fischeri bioluminescent strain which is used to quantitatively assess sample toxicity and correct the analytical signal accordingly. Both sensory elements and substrates, Furimazine for the bioluminescent reporter strain and chlorophenol red-ß-D-galactopyranoside for colorimetric detection of ß-gal, were integrated in the paper sensor to provide a stable all-in-one disposable cartridge which can be easily snapped into a smartphone with a clover-shaped 3D printed housing. This is the first integration of bioluminescence and colorimetric detection on a smartphone-paper sensor, providing a readout within 15 and 60 min for the colorimetric and bioluminescent detection respectively. The biosensor was applied to water samples spiked with different concentrations of mercury, interferents and toxic chemicals providing a limit of detection for Hg(II) at the ppb levels.

Enzymatic Digestion of Calf Fleshing Meat By-Products: Antioxidant and Anti-Tyrosinase Activity of Protein Hydrolysates, and Identification of Fatty Acids.

The food waste reduction through an efficient recovery of its valuable building molecules has become an important topic with a positive effect on the economy and the environment. In this work, the revalorization of slaughterhouse calf fleshing meat through its enzymatic hydrolysis is proposed. The proteolytic activity of 11 enzymes was initially screened and the four most efficient enzymes (papain, trypsin, pancreatin, and bromelain) were selected. The molecular profiling of the different protein/peptide fractions by the Linear Trap Quadrupole-OrbiTrap technique showed compositional differences due to the specificity of the enzymes' cleavage sites. In order to find a potential reuse of these hydrolysates, the analysis of antioxidant and, for the first time on fleshing meat hydrolysates, of anti-tyrosinase activities, was performed. Papain-digested samples were those showing the highest inhibition activity of tyrosinase enzyme (55.6%) as well as the highest antioxidant activity (3.52 g TEAC/L). In addition, the composition analysis of the lipid fraction was performed. The mono-unsaturated fatty acids resulted to be the most abundant lipid in all the samples with the exception of pancreatin-treated hydrolysates in which poly-unsaturated fatty acids were predominant. The present results seemed to support a possible valorization of isolated fractions from calf fleshing by-products, as food or feed ingredients, by the implementation of fraction isolation within the meat-processing pipeline.

Extraction and Chemical Characterization of Functional Phenols and Proteins from Coffee (Coffea arabica) By-Products.

Not all the coffee produced goes to the roasting stage, because non-compliant green coffee beans are usually discarded by roasters and the silverskin of the coffee is usually removed and discarded. In the present work, non-compliant green coffee beans and coffee silverskins were fully characterized from a chemical point of view. In addition, enzyme-assisted extraction was applied to recover a fraction rich in proteins and polyphenols, tested for antimicrobial, antityrosinase, and antioxidant activities. Non-compliant green coffee beans showed higher amounts of polyphenols, flavanols, flavonoids, and caffeine than coffee silverskins (which were richer in tannins). The enzymatic extraction of non-compliant coffee green beans produced extracts with a good protein content and with a consistent quantity of polyphenols. The extract showed antioxidant, antityrosinase, and antimicrobial activity, thus representing a promising strategy to recover defective green coffee beans. The antioxidant and antimicrobial activity of coffee silver skins is lower than that of non-compliant coffee green beans extracts, while the antityrosinase activity is comparable.

Stress responses and nickel and zinc accumulation in different accessions of Stellaria media (L.) Vill. in response to solution pH variation in hydroponic culture.

In most non-hyperaccumulating plants, Ni and Zn uptake is negatively correlated with soil pH, however, few studies so far have investigated how pH influences the activity and uptake of Ni and Zn in plants grown in a hydroponic system, which generally allows culture variables to be singularly manipulated. In this study, the non-accumulator Stellaria media (L.) Vill. (Caryophyllaceae) had opposite trends of Ni and Zn uptake along a pH gradient (between 5 and 8 for Zn and between 5 and 6.5 for Ni), when grown in hydroponics. In all treatments, the solution metal concentration was fixed at 0.1 mM Ni or 0.55 mM Zn. Nickel accumulation increased with increasing pH with an average concentration in shoots of 167 µg/gDW at pH 5 and of 250 µg/gDW at pH 6.5. In contrast, Zn accumulation decreased with increasing pH, with an average concentration in shoots varying from 1640 µg/gDW, at pH 5, to 435 µg/gDW at pH 8. Assessment of total polyphenol and flavonoid contents and of antioxidant activity showed that these parameters were positively correlated with Ni or Zn accumulation in S. media shoots, while photosynthetic pigments content and root and shoot biomass were negatively correlated with Ni and Zn accumulation. The study was carried out on five different S. media populations, which did not show differences in relation to the accumulation of metals and synthesis of antioxidant compounds, nonetheless showing a different biomass production under control conditions.