Inhibition Of Peroxidase Activity Research Articles

Reactive oxygen species act as the key signaling molecules mediating light-induced anthocyanin biosynthesis in Eucalyptus

Light plays a pivotal role in regulating anthocyanin biosynthesis in plants, and the early light-responsive signals that initiate anthocyanin biosynthesis remain to be elucidated. In this study, we showed that the anthocyanin biosynthesis in Eucalyptus is hypersensitive to increased light intensity. The combined transcriptomic and metabolomic analyses were conducted on Eucalyptus leaves after moderate (ML; 100 μmol m−2 s−1) and high (HL; 300 μmol m−2 s−1) light intensity treatments. The results identified 1940, 1096, 1173, and 2756 differentially expressed genes at 6, 12, 24, and 36 h after HL treatment, respectively. The metabolomic results revealed the primary anthocyanin types, and other differentially accumulated flavonoids and phenylpropane intermediates that were produced in response to HL, which well aligned with the transcriptome results. Moreover, biochemical analysis showed that HL inhibited peroxidase activity and increased the ROS level in Eucalyptus leaves. ROS depletion through co-application of the antioxidants rutin, uric acid, and melatonin significantly reduced, and even abolished, anthocyanin biosynthesis induced by HL treatment. Additionally, exogenous application of hydrogen peroxide efficiently induced anthocyanin biosynthesis within 24 h, even under ML conditions, suggesting that ROS played a major role in activating anthocyanin biosynthesis. A HL-responsive MYB transcription factor EgrMYB113 was identified to play an important role in regulating anthocyanin biosynthesis by targeting multiple anthocyanin biosynthesis genes. Additionally, the results demonstrated that gibberellic acid and sugar signaling contributed to HL-induced anthocyanin biosynthesis. Conclusively, these results suggested that HL triggers multiple signaling pathways to induce anthocyanin biosynthesis, with ROS acting as indispensable mediators in Eucalyptus.

Effects of Zinc Compounds on the Enzymatic Activities of Lysozyme and Peroxidase and Their Antifungal Activities.

This study aimed to investigate the effects of zinc compounds on the enzymatic activities of lysozyme, peroxidase, and the glucose oxidase-mediated peroxidase (GO-PO) system and their antifungal activities. Four different zinc compounds (zinc chloride, gluconate, lactate, and sulfate) were incubated with hen egg-white lysozyme (HEWL), bovine lactoperoxidase (bLPO), the GO-PO system, and human unstimulated whole saliva in solution and on a hydroxyapatite surface. Enzymatic activities of lysozyme, peroxidase, and the GO-PO system were measured through the hydrolysis of Micrococcus lysodeikticus, oxidation of fluorogenic 2',7'-dichlorofluorescin, and glucose assay, respectively. Interactions between zinc and enzymes were analyzed by surface plasmon resonance (SPR). The minimum inhibitory concentration (MIC) and candidacidal activities of zinc compounds were examined against three Candida albicans strains. Zinc gluconate and sulfate significantly increased the enzymatic activities of salivary lysozyme in the solution assay and of HEWL and salivary lysozyme on the hydroxyapatite surface. However, all examined zinc compounds significantly decreased the enzymatic activities of bLPO and salivary peroxidase in solution and on the surface. SPR analyses revealed binding of zinc to lysozyme and peroxidase, with affinity differing according to the zinc compounds. The MIC of zinc compounds against C. albicans was 1.0-2.4mM. Candidacidal activities were 17.7-38.8% and 23.7-47.0% at 1.0 and 10mM concentrations, respectively. In conclusion, zinc compounds enhanced lysozyme activity but inhibited peroxidase activity. Zinc compounds exhibited concentration-dependent candidacidal activity against C. albicans. Zinc compounds are potential therapeutic agents for oral health, especially for geriatric patients.

Multicolor Hg2+ sensor based on the regulation of peroxidase activity of Fe/Co-MIL-88(NH2) and etching of gold nanobipyramids

The entry of Hg2+ into the human body can lead to serious damage to some organs and it is vital to construct some simple but sensitive Hg2+ assay methods. A multicolor sensor for Hg2+ was constructed depended on the inhibition of peroxidase activity of Fe/Co-MIL-88(NH2) mediated by DNA and color change caused by the etching of gold nanobipyramids (Au NBPs). The enzymatic activity of Fe/Co-MIL-88(NH2) can be inhibited by adsorbing the T-rich oligonucleotide sequence on its surface. Hg2+ can combine with thymine of the T-rich oligonucleotide sequence to constitute T-Hg2+-T complex, and cause the transforming of T-rich oligonucleotide sequence into three-dimensional structure and desorbed from Fe/Co-MIL-88(NH2) surface. Which results in the restoration of the peroxidase activity of Fe/Co-MIL-88(NH2), and then it catalyzes the 3,3′,5,5′-tetramethylbenzidine (TMB) to engender TMB2+, TMB2+ can etch Au NBPs, this accompanied with a peak shift of the UV–vis spectrum and recognizable color changes of the system. Semi-quantitative can be realized using the multicolor changes of the Au NBPs as the reading mode. Furthermore, quantitative sensing can be achieved by measuring the UV–vis peak shift of the system. The linear response range is 1.0 nM–10 µM, and the detection limit (LOD) is 0.28 nM.

Post-harvest melatonin application reduced browning in minimally processed lettuce (Lactuca sativa L.) during low temperature storage

The investigation was carried out to assess the effect of post-harvest dipping of minimally processed fresh cut lettuce with various concentrations (10, 100 and 1000 μmolL-1) of melatonin on shelf-life and sensory quality of lettuce stored at 6±2ºC for 8 days. Melatonin treatment was found effective in maintaining freshness and sensory quality of lettuce during storage. Browning was reduced by 45% and visual quality index increased by 44.10% compared to control in 100 μmol L-1 melatonin treated samples on the 6th day of storage. Maximum total chlorophyll, total phenol and total antioxidants and least activity of browning related enzyme i.e., peroxidase (POD) was observed in 100 μmol L-1 melatonin treated samples during storage. No significant variation was observed between 10 μmol L-1 melatonin treated and control samples. Browning index value had significant negative correlation with total chlorophyll, total phenol and total antioxidants whereas POD activity had significant positive correlation. It can be inferred from the present investigation that post-harvest treatment of 100 μmol L-1 melatonin extended shelf-life of minimally processed lettuce for 6 days by preserving phenols, chlorophyll, antioxidants and inhibiting POD activity.

Enzymatic activity and quality characteristics of melon juice processed by high‐intensity pulsed light

SummaryThe aim of this study was to explore the use of pulsed light (PL) for inactivating peroxidase (POD), polyphenoloxidase (PP0) and pectin methylesterase (PME) in melon juice. The influence of treatments on the optical, physicochemical and rheological properties of the juice was also evaluated. PL fluences between 3.6 and 71.6 J cm−2 caused a significant reduction in POD activity from 13% to 96% respectively. On contrary, PPO and PME activities were slightly or not significantly affected by the treatments. POD inactivation curve was successfully fitted with the first‐order and Weibull‐type models. Samples exposed to 35.8 and 71.6 J cm−2 showed minor changes in pH, titratable acidity and total soluble solids content than non‐treated juice along cold storage. PL treatments also better maintained the original colour of the fresh juice during storage. A slight but significant reduction in the apparent viscosity was observed due to PL exposure. Results indicated that pulsed light could be a useful technique for inhibiting POD activity and preserving the colour of melon juice along cold storage. Other preservation agent(s) in combination would need to be evaluated for better control of enzyme activity.

The Toxicity of Salicylhydroxamic Acid and Its Effect on the Sensitivity of Ustilaginoidea virens to Azoxystrobin and Pyraclostrobin.

Rice false smut (RFS) caused by Ustilaginoidea virens has been one of the most severe rice diseases. Fungicide-based chemical control is a significant measure to control RFS. In the sensitivity determination of quinone outside inhibitor (QoI) fungicide in vitro, salicylhydroxamic acid (SHAM) has been commonly added to artificial culture media in order to inhibit alternative oxidase of phytopathogenic fungi. However, some studies showed that artificial media should not include SHAM due to its toxicity. Whether SHAM should be added in the assay of U. virens sensitivity to QoI fungicide remains unknown. In this study, two appropriate media, potato sucrose agar (PSA) and minimal medium (MM), were selected to test SHAM toxicity and sensitivity of U. virens to azoxystrobin and pyraclostrobin. The mycelial growth and sensitivity to azoxystrobin and pyraclostrobin had no significant difference between on PSA and MM. SHAM could significantly inhibit mycelial growth, conidial germination, peroxidase (POD) and esterase activity of U. virens. Average effective concentration for inhibiting 50% (EC50) values of SHAM against mycelial growth of ten U. virens were 27.41 and 12.75 μg/mL on PSA and MM, respectively. The EC50 values of SHAM against conidial germination of isolates HWD and JS60 were 70.36 and 44.69 μg/mL, respectively. SHAM at 30 μg/mL significantly inhibited POD and esterase activity of isolates HWD and JS60, and even SHAM at 10 μg/mL significantly inhibited POD activity of isolate HWD. In addition, SHAM significantly reduced EC50 values and EC90 values of azoxystrobin and pyraclostrobin on both PSA and MM. Even in the presence of SHAM at 10 μg/mL, average EC50 values of ten U. virens isolates for azoxystrobin decreased 1.7-fold on PSA and 4.8-fold on MM, and for pyraclostrobin that decreased 2.8-fold on PSA and 4.8-fold on MM. Therefore, these results suggest that SHAM should not be included in artificial media in the assay of U. virens sensitivity to QoI fungicides.

Hydrogen-rich water alleviates chilling injury-induced lignification of kiwifruit by inhibiting peroxidase activity and improving antioxidant system.

Kiwifruit is prone to chilling stress and displays chilling injury (CI) such as lignification; however, the underlying physicochemical mechanism remains largely unknown. Here, the changes in levels of quality attributes, lignin biosynthesis, antioxidant system and sugars were compared in kiwifruit between control and hydrogen-rich water (HRW) treatments during cold storage for 90 days at 0°C. The results reveal that HRW is an effective measure for CI alleviation, as indicated by the decrease in lignification level with repressed peroxidase activity but enhanced polyphenol oxidase activity. The amelioration of membrane peroxidation was suggested by the repressed levels of H2 O2 and malondialdehyde. They were accompanied by the improvement of antioxidant system, which is supported by the enhancement of sugars including fructose and glucose. In conclusion, HRW can enhance chilling tolerance, as suggested by the alleviation of lignification through inhibiting peroxidase activity and elevating the antioxidant system to attenuate membrane peroxidation. © 2022 Society of Chemical Industry.

The effect of flavane-3, 4-diol on the yellowing of fresh-cut water chestnuts

Yellowing was the main reason for the deterioration of the edible quality of fresh-cut water chestnuts (FCWCs). Flavane-3, 4-diol could inhibit the yellowing of FCWCs, but its mechanism was unclear. The objective of this study was to elucidate the mechanism of flavane-3, 4-diol inhibiting the yellowing of FCWCs. Yellowing degree, eriodictyol concentration, naringenin concentration, polyphenol oxidase activity, peroxidase activity, phenylalanine lyase activity, number of thermophilic bacteria colonies, and number of yeasts and molds colonies of the control and the FCWCs treated by flavane-3, 4-diol were analyzed. The results indicated that flavane-3, 4-diol inhibited the yellowing of FCWCs by decreasing the yield of eriodictyol and reducing peroxidase activity. The effects of flavane-3, 4-diol on naringenin concentration, polyphenol oxidase activity, phenylalanine lyase activity, number of thermophilic bacteria colonies, and number of yeasts and molds colonies of FCWCs were not significant. Further, the type of flavane-3, 4-diol inhibiting peroxidase activity was investigated. The result indicated that the inhibition type was a kind of competitive inhibition and flavane-3, 4-diol and phenols competed for the active center of peroxidase. The results indicated that flavane-3, 4-diol might be used to inhibit the yellowing of FCWCs in practice.

Peroxidase from waste cabbage (Brassica oleracea capitata L.) exhibits the potential to biodegrade phenol and synthetic dyes from wastewater

Peroxidases are well known for their ability to biodegrade some recalcitrant organic pollutants like phenol and their derivatives resulting in a reduction in their toxicity. The present study was designed to extract, characterize, and evaluate the potential of partially purified peroxidase from discarded and decaying waste cabbage leaves in the biodegradation of phenol and some common synthetic azo dyes. This was done by first partially purifying the crude extract of waste cabbage peroxidase (WCP) using ammonium sulfate precipitation, dialysis, and gel filtration chromatography. Thereafter, the experimental determination of protein concentration, peroxidase activity, and biodegradation of phenol and azo dyes was done spectrophotometrically. The results showed a purification fold of 87.65 with a 34.92% yield. The partially purified peroxidase had its optimum activity at temperature 30 °C, pH 5.5 while showing broad substrate preference with ABTS been the substrate. The stability studies also showed that WCP was stable over a wide range of pH (4.0–7.0) and 41% of its original activity was retained at 80 °C indicating that it is a thermostable enzyme. The kinetic data of WCP showed Km values of 1.24, 17.89, and 19.24 mM and Vmax values of 1111.11, 909.09, and 588.24 mM /minutes for ABTS, guaiacol, and o-dianisidine respectively. Three metal ions, Hg2+, Cu2+, Ni2+, organic solvent (acetone), EDTA, and urea inhibited peroxidase activity; whereas Mn2+ and Zn2+ showed slight activation. The partially purified WCP exhibited high efficiency for the biodegradation of synthetic azo dyes and phenol at the lab-scale. After 48 h incubation, the waste cabbage peroxidase efficiently catalyzed the decolorization of tested azo dyes at varying degrees; azo blue 5, azo purple, azo yellow 6, and citrus red 2, with a percentage decolorization of 85.1, 69.1, 46.2 and 42.9%, respectively. The waste cabbage peroxidase also shows up to 91.1% efficiency for degradation of phenol in aqueous solution after 60 min. Findings from this study provide promising evidence on the possibility of utilizing/recycling a readily abundant waste cabbage to useful bioproducts like peroxidase enzyme with the ability to biodegrade azo dyes and phenol at a small scale in the laboratory. Moreover, the findings from this study increase the prospect of waste cabbage peroxidase for the treatment of industrial effluents containing dyes and phenolic pollutants. The approach of transforming waste from one source into a useful biocatalyst that can potentially be exploited to treat waste pollutants from a different source offers a chain of green technology.

Effect of 5-Aminolevulinic Acid (ALA) on the Biochemical and Physiological Parameters of Postharvest Quality of Polygonatum multiflorum L. All. ‘Variegatum’ Cut Foliage

Due to the dynamic development of the floriculture market, new species and varieties of plants that can potentially be used as a source of cut greenery are constantly being sought. The experiment was conducted to analyze the effect of the cultivation site (unheated foil tunnel and open field) and treatments with the Pentakeep V formulation (0.00%, 0.02%, 0.04%, and 0.06%) on the vase life and postharvest quality of Polygonatum multiflorum ‘Variegatum’ cut foliage. There was a positive effect of the cultivation in the unheated foil tunnel on the vase life and biochemical parameters, namely the electrolyte leakage (EL), thiobarbituric acid reactive substances (TBARS), chlorophyll a + b (Chl. a + b), proline, peroxidase (POD), and ascorbate peroxidase (APX), of P. multiflorum cut foliage. Foliar application of Pentakeep V formulation at concentrations of 0.04% and 0.06% contributed to a decrease in the TBARS content in the P. multiflorum cut leaves, regardless of the plant cultivation site. Additionally, it reduced proline production in cut leaves of P. multiflorum cultivated in the unheated foil tunnel, which was confirmed by the analyses carried out after the 30 days of the experiment. Furthermore, the exogenous application of ALA during P. multiflorum cultivation inhibited POD activity, irrespective of its concentration and the site of plant cultivation.

Application of Azospirillum brasilense Lipopolysaccharides to Promote Early Wheat Plant Growth and Analysis of Related Biochemical Responses

While the effects of lipopolysaccharides (LPS) of plant pathogenic bacteria in induction of plant defense responses have been characterized, the role of LPS of beneficial rhizobacteria on plant growth is less clear. In this study, we assessed the in vitro effects of LPS from the rhizobacterium Azospirillum brasilense Sp245 on early growth of wheat seedlings (Triticum aestivum) and on some biochemical responses related to growth, like peroxidase (POD) enzyme activity and Ca2+ availability. Four days after treating the seedlings with various concentrations of A. brasilense LPS (10 to 1000 µg/mL), the growth of the seedlings was enhanced as evidenced by significant increase in leaf and root lengths as well as fresh weight. These increases were comparable to those resulting from inoculation with the rhizobacteria. POD enzyme activity increased significantly in roots treated with LPS and was concentration dependent. Salicylhydroxamic acid, an inhibitor of peroxidase activity, decreased POD activity and plant growth promoted by LPS. Lanthanum, an inhibitor of calcium channels, and EGTA, inhibited plant growth and POD activity promoted by LPS, while the calcium ionophore A23187 alone was able to increase plant growth and POD activity. In summary, the results suggest that isolated LPS of A. brasilense have the capacity to promote early wheat seedling growth and that POD enzyme activity and Ca2+ levels are involved in the LPS-mediated biological activity.

High resolution structural and functional analysis of a hemopexin motif protein from Dolichos

It is increasingly evident that seed proteins exhibit specific functions in plant physiology. However, many proteins remain yet to be functionally characterized. We have screened the seed proteome of Dolichos which lead to identification and purification of a protein, DC25. The protein was monomeric and highly thermostable in extreme conditions of pH and salt. It was crystallized and structure determined at 1.28 Å resolution using x-ray crystallography. The high-resolution structure of the protein revealed a four-bladed β-propeller hemopexin-type fold containing pseudo four-fold molecular symmetry at the central channel. While the structure exhibited homology with 2S albumins, variations in the loops connecting the outermost strands and the differences in surface-charge distribution may be relevant for distinct functions. Comparative study of the protein with other seed hemopexins revealed the presence of four conserved water molecules in between the blades which cross-link them and maintain the tertiary structure. The protein exhibited intrinsic peroxidase activity, which could be inhibited by binding of a heme analog. The identification of redox-sensitive cysteine and inhibition of peroxidase activity by iodoacetamide facilitated characterization of the possible active site. The determined peroxidase activity of DC25 may be responsible for rescuing germinating seeds from oxidative stress.

Effects of SHAM on the Sensitivity of Sclerotinia sclerotiorum and Botrytis cinerea to QoI Fungicides.

It is a common practice to add salicylhydroxamic acid (SHAM) into artificial medium in the in vitro sensitivity assay of fungal phytopathogens to the quinone outside inhibitor (QoI) fungicides. The rationale for adding SHAM is to inhibit fungal alternative oxidase, which is presumed to be inhibited by secondary metabolites of plants. Therefore, the ideal characteristics of SHAM should be almost nontoxic to phytopathogens and have no significant effect on control efficacy of fungicides. However, this study showed that the average effective concentration for 50% inhibition (EC50) of mycelial growth values of SHAM were 97.5 and 401.4 μg/ml for Sclerotinia sclerotiorum and Botrytis cinerea, respectively. EC50 values of the three QoI fungicides azoxystrobin, kresoxim-methyl, and trifloxystrobin in the presence of SHAM at 20 and 80 μg/ml for S. sclerotiorum and B. cinerea, respectively, declined by 52.7 to 78.1% compared with those without SHAM. For the dicarboximide fungicide dimethachlone, the average EC50 values in the presence of SHAM declined by 18.2% (P = 0.008) for S. sclerotiorum and 35.9% (P = 0.012) for B. cinerea. Pot experiments showed that SHAM increased control efficacy of the three QoI fungicides against the two pathogens by 43 to 83%. For dimethachlone, SHAM increased control efficacy by 134% for S. sclerotiorum and 86% for B. cinerea. Biochemical studies showed that SHAM significantly inhibited peroxidase activity (P = 0.024) of B. cinerea and esterase activity (P = 0.015) of S. sclerotiorum. The strong inhibitions of SHAM per se on mycelial growth of B. cinerea and S. sclerotiorum and significant influences on the sensitivity of the two pathogens to both the QoI fungicides and dimethachlone as well as inhibitions on peroxidase and esterase indicate that SHAM should not be added in the in vitro assay of sensitivity to the QoI fungicides.

Natural dicarbonyls inhibit peroxidase activity of peroxiredoxins

It has been established that the activity of recombinant human peroxiredoxins (Prx1, Prx2, Prx4 and Prx6) inhibits by natural dicarbonyls formed during free radical peroxidation of unsaturated lipids (malonic dialdehyde) and oxidative transformations of glucose (glyoxal, methylglyoxal). The possible role of peroxiredoxins activity decreasing under oxidative and carbonyl stress is discussed as an important factor that includes molecular mechanisms of vascular wall damage in atherosclerosis and diabetes mellitus.

Use of intravenous paracetamol for patent ductus arteriosus closure in preterm and very low birth infants

The patent ductus arteriosus contributes to common morbidities in premature infants.Ductal closure may require pharmocological management and/or surgical ligation up to 70% of time in extremely low birth infants. Ductal closure utilising NSAIDs has many adverse effects related to their vasoconstrictive effects on renal cerebral and mesentric vessels. While NSAIDS are known to inhibit COX activity via Arachidonic acid pathway, acetaminophen inhibits peroxidase activity. It seems to be a reasonable optionto consider for PDA closure, especially in those infants for which NSAIDSmay be contraindicated. Place of study: A prospective study in Neonatal intensive care unit 1. Maternity and childrens hospital. Makkah. Patients: preterms and extreme preterms-24–30 weeks, Birth weight 450 g-1.2 Kg with haemodynamically significant PDA. iNTERVENTION: iv PARACETAMOL −15 MG/kG/dose Q 6 hrly × 3–5 days with parenteal consent. 1. Total no: of admissions in NICU-1 1150. For 20 months from 8/1437 to 3/39. 2. 100 patients had haemodynamically significant PDA where NSAIDs were contraindicated. 3 24-26 wks 20 27–29 wks 50 30–32 wks 30 4. weight wise distribution. <1 kg 1–1.5 Kg 1.5–2 kg. 45 52 3 5 male: female. M 53 F 47 1. −32% had PNA. 2–13% had CPR at birth. 3 −40% had IVH of which 11% had gradeIII-iv IVH. 4. −35% had pulmonary haemorrhage. 5 −13% had pneumothorax. 6. −61% had CLD. 7. −86% had hypotension 8. – 100% were NPO. 9. All had central line. 10. 90% had renal impairment. 11–95% had electrolyte imbalance either before or after treatment. 12 49% had +ve blood culture. 13. thrombocytopenia was noticed in 50% of them. 14 80% were discharged home 20% expired. PDA: echo first done: 1–7 days. 80% 2nd/3rd day. Duration of paracetamol: 3–5 days. Effective closure after 1st dose-44%. Effective closure after 2nd course of paracetamol-21%. NSAIDS used after paracetamol in 10%. Hydrochlorthiazide used in 8%. PDA reopened due to sepsis-7%. Intravenous paracetamol can be safely used in extreme low birth infants.

Inhibition of Peroxidase Activity by Methylxanthines

Introduction: Peroxidase (POD) is an important antioxidant enzyme that catalyzes oxidation of a number of organic and non-organic substrates using hydrogen peroxide as the electron acceptor. At physiological low levels, reactive oxygen species (ROS) can act as redox messengers in the regulation of intracellular signaling. However, in excess amounts they can suppress the immune system and cause oxidative stress. Considering the high consumption of tea and coffee as the most common drink in the world, in the present study the effect of caffeine and theophylline on the activity of POD has been investigated. Materials and Methods: The activity of POD was measured by following absorption at 510 nm due to the oxidation of 4-aminoantipyrine in the absence and presence of caffeine and theophylline. The enzyme kinetic parameters were then measured and compared in each case. Results: It was shown that both methylxanthines acted as inhibitors with IC50' the amount of inhibitor to reduce the enzyme activity by 50%, of 0.6 and mM 0.55 mM for caffeine and theophylline respectively. The kinetic constants, Km and Vmax' indicated that both inhibitors worked by an un-competitive mechanism on POD activity. The values of Ki were calculated as 0.08 and 0.045 mM for caffeine and theophylline respectively. Conclusions: Lower values of IC50 and Ki for theophylline compared to caffeine, led us to a final conclusion that theophylline is a stronger inhibitor of POD than caffeine.

Sources for developing new medicinal products: biochemical investigations on alcoholic extracts obtained from aerial parts of some Romanian Amaryllidaceae species

BackgroundAlthough Galanthus nivalis L. (snowdrop) is known for the galanthamine content, used in the treatment of Alzheimer disease, the polyphenolic compounds of Amaryllidaceae species are less studied. Proper understanding of the polyphenolics in these extracts and of their antioxidant and antimicrobial properties may allow a reconsideration of their medicinal uses.MethodsThe polyphenolic content of four selected Amaryllidaceae species harvested from Romania (Galanthus nivalis L., Narcissus pseudonarcissus L., N. poeticus L. and Leucojum vernum L.) was determined by spectrophotometric methods; the identification of phenolic compounds was performed by a HPLC-MS method, in order to establish their polyphenolic fingerprints. For the evaluation of the antioxidant potential the following methods were employed: DPPH radical scavenging, FRAP, hemoglobin ascorbate peroxidase activity inhibition (HAPX), inhibition of lipid peroxidation catalyzed by cytochrome c, and electron paramagnetic resonance (EPR) spectroscopy assays. Antimicrobial activity was assessed using the disc diffusion method.ResultsQualitative and quantitative analyses highlight important amount of polyphenols (over 15 mg/g); the main identified compounds are chlorogenic and p-coumaric acids in all species. Only G. nivalis shows antioxidant activity by all the used methods. G. nivalis and L. vernum strongly inhibits the growth of S. aureus, while N. poeticus shows a very good antifungal activity.ConclusionsThe results of this study provide a new approach to the properties and therapeutic uses of some Romanian widespread Amaryllidaceae species that could be considered sources of developing new medicinal products with anti anti-staphylococcal and antifungal activity.

Thiazole Orange-Modified Carbon Dots for Ratiometric Fluorescence Detection of G-Quadruplex and Double-Stranded DNA.

A new carbon dot (CD)-based nanoprobe for the ratiometric fluorescence detection of DNA was constructed in this work. Thiazole orange (TO), a specific organic small molecular probe toward DNA, is covalently linked to the surface of CDs, acting as the recognition element and the fluorescence response unit. In the absence of DNA, the nanoprobe only emitted the blue fluorescence of CDs, whereas TO was almost nonfluorescent. Upon addition of DNA, a turn-on emission at 530 nm appeared and gradually enhanced along with the increasing of the target DNA, whereas the fluorescence of CDs was unchanged, which realized the ratiometric detection of the target DNA. The CD-TO nanoprobe showed good selectivity to parallel G-quadruplex (G4) and double-stranded (ds) DNA over antiparallel G4 and single-stranded DNA. Moreover, the ratiometric fluorescence nanoprobe exhibited high sensitivity for ssab (a dsDNA) and c-myc (a parallel G4) with a low detection limit of 0.90 and 3.31 nM, respectively. Additionally, the G4/hemin peroxidase activity inhibition experiment demonstrated that CD-TO bound to the G4s through the end-stacking mode.

Ag+ -Gated Surface Chemistry of Gold Nanoparticles and Colorimetric Detection of Acetylcholinesterase.

Chemical regulation of enzyme-mimic activity of nanomaterials is challenging because it requires a precise understanding of the surface chemistry and mechanism, and rationally designed applications. Herein, Ag+ -gated peroxidase activity is demonstrated by successfully modulating surface chemistry of cetyltrimethylammonium bromide-capped gold nanoparticles (CTAB-AuNPs). A surface blocking effect of long-chain molecules on surfaces of AuNPs that inhibit peroxidase activity of AuNPs is found. Ag+ ions can selectively bind on the surfaces of AuNPs and competitively destroy CTAB membrane forming Ag+ @CTAB-AuNPs complexes to result in enhanced peroxidase activity. Ag+ @CTAB-AuNPs show the highest peroxidase activity compared to similar-sized citrate-capped and ascorbic acid-capped AuNPs. Ag+ @CTAB-AuNPs can potentially develop into analyte-responsive systems and exhibit advantages in the optical sensing field. For example, the Ag+ @CTAB-AuNPs system shows an enhanced sensitivity and selectivity for acetylcholinesterase activity sensing compared to other methods.

Inhibition of Enzymatic and Oxidative Process by Phenolic Extracts from Spirulina sp. and Nannochloropsis sp.

SUMMARYThis study investigates the capacity of phenolic extracts from microalgae Nannochloropsis sp. and Spirulina sp. to inhibit enzymes and free radical activities, intending to find an innovative way to slow down food damage. HPLC-UV and LC-MS/MS served to determine and confirm, respectively, the phenolic acid profiles in the soluble methanolic (free phenolic) and ethanolic (conjugated phenolic) fractions, and after hydrolysis (bound phenolic fractions). Different procedures measured the antioxidant activity of the extracts to estimate the minimal concentration for the protective effect, stability and versatility of activity. The ability to inhibit the oxidative process (ABTS and DPPH), α-amylase and peroxidase activities were estimated as specific inhibition (%/(min·μg)) for better comparison between the phenolic sources. The phenolic acid mass fractions in the free phenolic extracts from Spirulina sp. and Nannochloropsis sp. were 628 and 641 μg/g, respectively. Phenolic extract from Nannochloropsis sp. showed the highest value of ABTS inhibition (1.3%/(min·μg)) and highest inhibition of peroxidase activity (0.4%/(min·μg)). The extract from Spirulina sp. was a better inhibitor of α-amylase activity (0.07%/(min·μg)). Therefore, the phenolic extracts from the edible microalgae may be applied in food industry as natural protector against endogenous and exogenous hydrolytic and oxidative processes.