Electron Spray Ionization Mass Spectrometry Research Articles

Studies of KP46 and KP1019 and the Hydrolysis Product of KP1019 in Lipiodol Emulsions: Preparation and Initial Characterizations as Potential Theragnostic Agents.

Lipiodol (iodized poppy seed oil) accumulates predominately in the tumor rather than in the liver tissue [1, 2]. Therefore, mixing anticancer drugs with Lipiodol may enhance the antitumor effect by increasing the local drug concentration. In this pilot study, we made use of Lipiodol as a potential carrier of three promising antitumor metal complexes (tris(8-quinolato)gallium(III) (KP46), tetrachlorobis(indazole)ruthenate(III) (KP1019) and the hydrolysis product of KP1019, mer,trans-[RuCl3(H2O)(Hind)2]. The stability of the drugs in Lipiodol and the release profile into the aqueous phase were examined independently by three different analytical techniques (high pressure liquid chromatography, HPLC; atom absorption spectroscopy, AAS; and electron spray ionization mass spectrometry, ESI-MS). The complexes were stable and remained in the Lipiodol emulsion over 3 days. In contrast to KP1019 and KP46, evaluation of Lipiodol emulsions of mer,trans-[RuCl3 (H2O) (Hind) 2] was not possible due to the insolubility of the compound in Lipiodol. KP1019 released rapidly into the aqueous phase in the first week and after 1 month it was not possible to detect the complex in the emulsion. KP46 showed a gradual release with the time resulting in the release of about 6.4 % of KP46 into the aqueous phase after 1 month of incubation. The initial results show that Lipiodol can be successfully employed as a carrier of anticancer Ru- or Ga-complexes. Furthermore, advantages can overcome the poor water solubility of the metal complexes, opening new perspectives for the use of Lipiodol emulsions in molecular imaging and cancer therapy as theragnostic agents.

Peptides derived from the histidine-proline rich glycoprotein bind copper ions and exhibit anti-angiogenic properties.

The role of copper in cancer progression has been established since decades. Additionally, copper is able to stimulate angiogenesis through the control of VEGF expression and activity in endothelial cells. In this paper a tetrapeptide, belonging to the histidine-proline-rich glycoprotein (HPRG) and encompassing four repeats of the sequence GHHPH (named TetraHPRG), was synthesized and its copper(ii) complex species were characterized by means of potentiometry, UV-vis, circular dichroism (CD), electron paramagnetic resonance (EPR) and electron spray ionization mass spectrometry (ESI-MS). Moreover, a peptide covalently bound through an amidic bond to trehalose (TH-TetraHPRG) was designed and synthesized as a prodrug system. The activity of both TetraHPRG and TH-TetraHPRG molecules on copper and VEGF induced angiogenic responses in endothelial cells was assessed. The two peptides show a similar and effective anti-angiogenic activity on both molecular and cellular responses. Since the trehalose derivative has a higher resistance to enzymatic degradation, it can be further exploited as a potential drug delivery system with anti-angiogenic activity.

Interactions of Polyaromatic Compounds. Part 2. Flocculation Probed by Dynamic Light Scattering and Molecular Dynamics Simulation

In part 1 of this series of papers, the results of electron spray ionization mass spectrometry (ESI-MS) and molecular dynamics (MD) simulation revealed a close relationhsip between nanoaggregation of polyaromatic (PA) compounds and their chemical structures. In this paper, we present the results of investigating the flocculation of fractionated asphaltenes and synthesized PA molecules by dynamic light scattering (DLS). Together, these two papers complement one another and draw a full picture of asphaltene aggregation. Three asphaltene fractions were obtained on the basis of their different adsorption characteristics onto calcium carbonate. The DLS results suggest that the irreversibly adsorbed (Irr-Ads) asphaltenes containing the highest number of polar groups are the fraction of asphaltenes responsible for the observed flocculation in whole asphaltenes. To better understand the aggregation behavior of asphaltenes, flocculation of three synthesized PA compounds, N-(1-hexylhepyl)-N′-(5-carboxypentyl)peryle...

Efficient biodegradation of acephate by Pseudomonas pseudoalcaligenes PS-5 in the presence and absence of heavy metal ions [Cu(II) and Fe(III)], and humic acid.

The present study was intended to investigate the biodegradation of acephate in aqueous media in the presence and in the absence of metal ions [Fe(III) and Cu(II)], and humic acid (HA). Biodegradations were performed using Pseudomonas pseudoalcaligenes PS-5 (PS-5) isolated from the heavy metal polluted site. Biodegradations were monitored by UV-Visible, FTIR, and electron spray ionization-mass spectrometry (ESI-MS) analyses. ESI-MS analysis revealed that PS-5 degraded acephate to two metabolites showing intense ions at mass-to-charge ratios (m/z) 62 and 97. The observed kinetic was the pseudo-first order, and half-life periods (t1/2) were 2.79d-1 (of PS-5+acephate), 3.45d-1 [of PS-5+acephate+Fe(III)], 3.16d-1 [of PS-5+acephate+Cu(II)], and 5.54d-1 (of PS-5+acephate+HA). A significant decrease in degradation rate of acephate was noticed in the presence of HA, and the same was confirmed by UV-Visible and TGA analyses. Strong aggregation behavior of acephate with humic acid in aqueous media was the major cause behind the slow degradation rate of acephate . New results on acephate metabolism by strain PS-5 in the presence and in the absence of metal ions [Fe(III) and Cu(II)] and humic acid were obtained. Results confirmed that Pseudomonas pseudoalcaligenes strain PS-5 was capable of mineralization of the acephate without formation of toxic metabolite methamidophos. More significantly, the Pseudomonas pseudoalcaligenes strain PS-5 could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.

Antibacterial activity of Nepalese wild mushrooms against Staphylococcus aureus and Propionibacterium acnes

The present study aims to reveal the antibacterial potential of the wild mushrooms of Nepal. Despite the recognition of the medicinal potential of the natural resources in this country, a systematic study on the bioactivities of the wild mushrooms is still lacking. Therefore, in an attempt to fill this gap, ethanol extracts of 90 Nepalese wild mushroom samples were tested for antibacterial activity against Staphylococcus aureus and Propionibacterium acnes. Staphylococcus aureus was comparatively more susceptible with Inonotus clemensiae exhibiting the least minimum bactericidal concentration (MBC) of 100 μg/mL. The major compound in I. clemensiae was identified to be hispidin using high resolution liquid chromatography–electron spray ionization mass spectrometry (LC–ESI-MS) and nuclear magnetic resonance (NMR) analyses. Furthermore, the minimum inhibitory concentration (MIC) and MBC values of hispidin were determined to be 25 and 100 µg/mL for S. aureus and P. acnes, respectively. These findings show that the Nepalese wild mushrooms have the potential to be a novel addition to the functional ingredients industry due to their strong antibacterial potential.

Effect of Amine Functionalization and Ageing on Copper and Boron Leaching from Wood Preservatives Grafted to Siloxane Networks

The study evaluated copper, boron, and silicon release from wood samples treated with sol-gel formulations based on tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) functionalized with copper (II) chloride and boric acid, respectively. The adopted leaching procedure was Japanese protocol JIS K 1571 (2004). Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Electron Spray Ionization Mass Spectrometry (ESI-MS) were employed for analyzing the leached solutions. The obtained results highlighted the important role of the amine function that was derived from the APTES precursor, in anchoring both copper and boron through coordinative and ionic interactions, respectively. In fact, copper formulations with TEOS alone (without APTES) showed higher copper leaching. In contrast, the silicon leaching was decreased due to better siloxane reticulation performed by TEOS alone. In addition, ageing (two months) of the samples treated with APTES containing formulation TEOS/APTES/Cu 10:1:0.2 resulted in a reduction of copper leaching (from 27% in the fresh samples to 7% in the aged ones), which was attributable to increased efficiency of inorganic sol-gel polymerization. The TEOS/APTES/B 1:1:0.2 formulation gave a leaching value of 20%, which was lower in comparison with the values reported in previous literature.

A dihydrochalcone derivative and further steroidal saponins from Sansevieria trifasciata Prain.

Phytochemical investigation of the aerial parts of Sansevieria trifasciata, one of the most common Dracaenaceae plants, has resulted in the isolation of a new dihydrochalcone derivative named trifasciatine C (1), four previously unreported steroidal saponins as two pairs of inseparable regioisomers: trifasciatosides K/L (2/3), M/N (4/5), together with the known 1,2-(dipalmitoyl)-3-O-β-D-galactopyranosylglycerol (6), aconitic acid (7), and 1-methyl aconitic acid (8). Their structures were elucidated mainly by extensive spectroscopic analysis (1D and 2D nuclear magnetic resonance) and high-resolution electronspray ionization-mass spectrometry, as well as chemical methods and comparison of their spectral data with those of related compounds. Compounds 2/3 and 4/5 were evaluated for their antiproliferative activity on Hela cells, and no significant effect was observed.

Determination of Multiclass Harmful Residues in Shellfish Using LC-MS

A multi-residue procedure with liquid chromatography-tandem mass spectrometry analysis was developed to simultaneously detect the presence of 4 diarrheic shellfish poisoning toxins, 14 sulfonamides, chloramphenicol and thiamphenicol in shellfish tissues. Samples were first purified by a modified rapid procedure and separated on a ZOBRAX Eclipse Plus C18 column and quantified using electron spray ionization-mass spectrometry-mass spectrometry. The results showed that the limits of quantification (LOQ) of SPX1, OA-C, GYM, and PTX-2 were 1.0, 2, 0.5 and 2 μg/kg, respectively. The LOQ for the antibiotics was below acceptable limits established by most countries. Compared to the external standard method, this matrix matched the calibration method effectively, overcame the matrix effects and gave better quantitative results. Recoveries of spiked compounds ranged between 67.6% and 109.8%, with relative standard deviations below 15% for most target analytes. Only sulfathiazole had a %RSD of 18.6% at the lowest spiked concentration. The proposed method was accurate, rapid and reliable.https://doi.org/10.21423/jrs-v05n01p009 (DOI assigned 4/17/2019)

Kinetic Monte Carlo Generation of Complete Electron Spray Ionization Mass Spectra for Acrylate Macromonomer Synthesis

Absolute electron spray ionization mass spectrometry (ESI-MS) data are reported, for the first time, over the complete chain length range for the synthesis of well-defined macromonomers (MMs) obtained via activation of bromine-capped poly(n-butyl acrylate) (0.1 mass %; solvent: anisole; 140 °C) with CuBr2/Me6TREN (Me6TREN: tris(2-(dimethylamino)ethyl)amine) and tin ethylhexanoate. These data are generated based on bivariate kinetic Monte Carlo simulations, tracking the chain lengths and the positions of radicals/characteristic groups along the chains (>100 reactions, 12 radical/dormant species types, and 7 characteristic end/mid-groups). Based on qualitative tuning to experimental data, migration is found to be 50 times slower than backbiting but 15 times faster than βC-scission, making it a dominant reaction. Benefiting from the absence of monomer, the chain transfer to polymer rate coefficient is assessed as 6 × 102 L mol–1 s–1 (140 °C). Model analysis shows that consecutive backbiting/migration/βC-scis...

Product Distribution Control for Glucosamine Condensation: Nuclear Magnetic Resonance (NMR) Investigation Substantiated by Density Functional Calculations

Selective conversion of glucosamine (GlcNH2) to deoxyfructosazine (DOF) and fructosazine (FZ) with additives was investigated. Significantly enhanced yield of DOF can be improved to 40.2% with B(OH)3 as the additive. Chemical shift titration (via one-dimensional nuclear magnetic resonance (1D 1H and 13C NMR)) and two-dimensional nuclear magnetic resonance (2D NMR) including 1H–13C HSQC and 1H–1H COSY are used to investigate intermolecular interactions between B(OH)3 and GlcNH2. Diffusion-ordered NMR spectroscopy (DOSY) was further employed to identify intermediate species. Mechanistic investigation by NMR combined with electron spray ionization–mass spectroscopy (ESI-MS) discloses that a mixed 1:1 boron complex was identified as the major species, shedding light on the promotional effects of B(OH)3, which is substantiated by density functional theory (DFT). Boron coordination effects make ring-opening and subsequent dehydration reaction thermodynamically and kinetically more favorable. Dehydration of dihy...

Allosteric Transmission along a Loosely Structured Backbone Allows a Cardiac Troponin C Mutant to Function with Only One Ca2+ Ion

Hypertrophic cardiomyopathy (HCM) is one of the most common cardiomyopathies and a major cause of sudden death in young athletes. The Ca2+ sensor of the sarcomere, cardiac troponin C (cTnC), plays an important role in regulating muscle contraction. Although several cardiomyopathy-causing mutations have been identified in cTnC, the limited information about their structural defects has been mapped to the HCM phenotype. Here, we used high-resolution electron-spray ionization mass spectrometry (ESI-MS), Carr-Purcell-Meiboom-Gill relaxation dispersion (CPMG-RD), and affinity measurements of cTnC for the thin filament in reconstituted papillary muscles to provide evidence of an allosteric mechanism in mutant cTnC that may play a role to the HCM phenotype. We showed that the D145E mutation leads to altered dynamics on a μs-ms time scale and deactivates both of the divalent cation-binding sites of the cTnC C-domain. CPMG-RD captured a low populated protein-folding conformation triggered by the Glu-145 replacement of Asp. Paradoxically, although D145E C-domain was unable to bind Ca2+, these changes along its backbone allowed it to attach more firmly to thin filaments than the wild-type isoform, providing evidence for an allosteric response of the Ca2+-binding site II in the N-domain. Our findings explain how the effects of an HCM mutation in the C-domain reflect up into the N-domain to cause an increase of Ca2+ affinity in site II, thus opening up new insights into the HCM phenotype.

Cerebrosides, extracellular glycolipids secreted by the selective lignin-degrading fungus Ceriporiopsis subvermispora

Ceriporiopsis subvermispora is a selective white-rot fungus that degrades lignin at a site far from the hyphae and extracellular enzymes, without intensive damage to the cellulose. In selective ligninolysis, low molecular mass metabolites play a principal role and amphipathic substances are involved to control the degradation and transport of hydrophobic aromatic molecules, including lignin and lipids; however, secretion of the amphipathic substances by this fungus has not been well understood, except for alk(en)yl itaconates called ceriporic acids, which have a weak amphiphilicity. Herein, we report for the first time that the fungus secretes cerebrosides that are classified as glycosphingolipids. By using liquid chromatography electron spray ionization mass spectrometry (LC-ESI–MS) and nuclear magnetic resonance (NMR) spectroscopy coupled with stable isotope feeding experiments with 13C-glucose and 15N-ammonium sulfate, the cerebrosides were determined to be N-hydroxyoctadecanoyl-1-O-β-d-glucopyranosyl-4E,8E-sphingadienine, N-hydroxyoctadecanoyl-1-O-β-d-glucopyranosyl-4E,8Z-sphingadienine, and N-hydroxyoctadecanoyl-1-O-β-d-glucopyranosyl-9-methyl-4E,8E-sphingadienine. The cerebrosides are strong amphipathic substances and potential metabolites for regulating difference and symbiosis within the microbial community.

Isolation and Characterisation of a Proanthocyanidin With Antioxidative, Antibacterial and Anti-Cancer Properties from Fern Blechnum orientale.

Background:Blechnum orientale Linn. (Blechnaceae), a fern, is traditionally used in the treatment of various ailments, such as skin diseases, stomach pain, urinary bladder complaints, and also as a female contraceptive. Previously, we reported a strong radical scavenging activity, antibacterial activity and cytotoxicity against HT29 colon cancer cells by aqueous extract of B. orientale.Objective:In this study, we attempted to isolate and identify the active compound from the aqueous extract of B. orientale.Materials and Methods:Aqueous extract of B. orientale was subjected to repeated MCI gel chromatography, Sephadex-LH-20, Chromatorex C18 and semi-preparative high performance liquid chromatography and was characterized using nuclear magnetic resonance and electrospray ionization mass-spectrometry spectroscopic methods. Antioxidant activity was determined using 2, 2-diphenyl-1-picrylhydrazyl radical scavenging assay. Antibacterial assays were conducted using disc diffusion whereas the minimum inhibitory concentration (MIC) and minimum bactericidal concentration were determined using the broth microdilution assay. Cytotoxicity was assessed using thiazolylblue tetrazoliumbromide.Results:A polymeric proanthocyanidin consisting of 2-12 epicatechin extension units and epigallocathecin terminal units linked at C4-C8 was elucidated. Bioactivity studies showed strong radical scavenging activity (IC50 = 5.6 ± 0.1 µg/mL), antibacterial activity (MIC = 31.3-62.5 µg/mL) against five gram-positive bacteria and selective cytotoxicity against HT29 colon cancer cells (IC50 = 7.0 ± 0.3 µg/mL).Conclusion:According to our results, the proanthocyanidin of B. orientale demonstrated its potential as a natural source of antioxidant with antibacterial and anti-cancer properties.SUMMARY A bioactive proanthocyanidin was isolated from the aqueous extract of medicinal fern Blechnum orientale Linn and the structure was elucidated using NMR and ESI-MS spectral studies.The proanthocyanidin compound possessed strong radical scavenging activity (IC50 5.6 ± 0.1 µg/mL)The proanthocyaniding compound showed bactericidal activity against five gram-positive bacteria inclusive of MRSA (minimum inhibitory concentration, MIC and minimum bactericidal concentration, MBC 31.3-62.5 µg/mL).The proanthocyanidin compound is strongly cytotoxic towards cancer cells HT29 (IC50 7.0 ± 0.3 µg/mL), HepG2 (IC50 16 µg/mL) and HCT116 (IC50 20 µg/mL) while weakly cytotoxic towards the non-malignant Chang cells (IC50 48 µg/mL). Abbreviation used: CC: Column chromatography, DP: degree of polymerization, DPPH: 2,2-diphenyl-1-picrylhydrazyl, ESI-MS: electronsprayionisation mass-spectrometry, MBC: Minimum bactericidal concentration, MIC: Minimum inhibitory concentration, MTT: Thiazolyl Blue Tetrazolium Bromide, MRSA: methicillin-resistant Staphylococcus aureus, NMR: nuclear magnetic resonance, TLC: thin layer chromatography, PD: prodelphinidin

Analysis of flumequine enantiomers in rat plasma by UFLC-ESI-MS/MS.

In this study the analysis and confirmation of flumequine enantiomers in rat plasma by ultra-fast liquid chromatography coupled with electron spray ionization mass spectrometry (using propranolol as an internal standard [IS]) was developed and validated. Plasma samples were prepared by liquid-liquid extraction using methyl tert-butyl ether as the extraction solvent. Direct resolution of the R- and S-isomers was performed on a CHIRALCEL OJ-RH column (4.6×150mm, 5μm) using acetonitrile / 0.1% formic acid / 1mM ammonium acetate as the mobile phase. Detection was operated by electron spray ionization in the selected ion monitoring and positive ion mode. The target ions at m/z 262.1 and m/z 260.1 were selected for the quantification of the enantiomers and IS, respectively. The linear range was 0.5-500ng/mL. The precisions (coefficient of variation, CV%) and recoveries were 1.43-8.68 and 94.24-106.76%, respectively. The lowest quantitation limit for both enantiomers is 0.5ng/mL, which is sensitive enough to be applied to sample analysis in other related studies.

Evaluation of cellobiose dehydrogenase and laccase containing culture fluids of Termitomyces sp. OE147 for degradation of Reactive blue 21

This study evaluates culture filtrate, rich in cellobiose dehydrogenase and laccases, of Termitomyces sp. OE 147, in decolouration and degradation of Reactive blue (RB) 21. About 35% decolouration was achieved at low volumes of the culture supernatant without addition of external redox mediators. An optimized dye to culture fluid ratio (75ppm: 0.1ml) at a pH of 4–5 resulted in removal of colour by 60%. The degradation products of RB21 were analysed by Electron Spray Ionization-Mass Spectrometry and several small molecules (ofm/z 106–199) were detected. These were concluded to be o-Xylene, 2,3-Dihydro-1H-isoindole, Isoindole-1,3-dione, 2,Benzenesulfonyl-ethanol, (4-Hydroxy-phenyl)-sulfamic acid, 2,3-Dihydro-1H-isoindole-5-sulfonic acid and proposed to result from joint action of cellobiose dehydrogenase, laccase, peroxidases and unidentified oxidoreductases present in the culture fluids. Based on the products formed and the known reactions of these enzymes, a degradation pathway was proposed for RB21. The culture fluid was also effective in decolouration (by about 50%) and detoxification (by ∼25%) of the combined effluent collected from a local mill indicating a treatment process that bypasses use of H2O2 and toxic mediators.

Interferon-gamma activity is potentiated by an intracellular peptide derived from the human 19S ATPase regulatory subunit 4 of the proteasome

Hundreds of intracellular peptides that are neither antigens nor neuropeptides are present in mammalian cells and tissues. These peptides correspond to fragments of cytosolic, nuclear or mitochondrial proteins. Proteasome inhibition affects the levels of the intracellular peptides in human cell lines. Here, the effect of immuneproteasome expression on the intracellular peptide profile was evaluated, and its functional significance was investigated. The expression of the immuneproteasome in HeLa cells was induced by interferon gamma treatment, and the relative concentrations of the intracellular peptides were compared to those of the control cells using isotope labeling and electron spray mass spectrometry. One of the peptides identified, VGSELIQKY (EL28), corresponds to amino acids 251–259 of the human 19S ATPase regulatory subunit 4. This peptide was increased in the extracts of HeLa cells that had been treated with interferon gamma compared to those of control cells. In vitro, EL28 increased the chymotrypsin, trypsin and caspase-like proteasome activities. In vivo, when covalently linked to a cell-penetrating peptide, EL28 potentiated the ability of interferon gamma to stimulate the expression of the immuneproteasome β5i subunit and to increase the proliferation of CD8+ T-cells. The EL28/cell-penetrating peptide construct also improved and positively modulated the secondary IgG anti-bovine serum albumin immune responsiveness elicited in high antibody-responder mice. Together, these results suggest that EL28 is a functional intracellular peptide that can potentiate interferon gamma activity. Biological significanceThe functional identification of EL28 advances our understanding regarding the bioactive peptides generated by limited proteolysis within cells.

Biological detoxification of Aflatoxin B1 by Bacillus licheniformis CFR1

Aflatoxin B1 is the most harmful among the mycotoxins commonly present in food and feed, and it may lead to hepatocellular carcinoma in humans and animals. Therefore, limiting its exposure to humans and livestock is very much essential. The present study aims to isolate and characterize Aflatoxin B1 detoxifying bacteria from various sources, to develop a safe and environment-friendly strategy for Aflatoxin B1 management. Fifty-six bacteria were isolated using a media amended with coumarin as a sole carbon source. Seven strains showed more than 70% reduction of AFB1 in liquid culture media. Among them, isolate CFR1 reduced Aflatoxin B1 by 94.7%, and it was selected for further studies. CFR1 was identified as Bacillus licheniformis CFR1, by biochemical characterization and 16S rRNA gene sequencing. The cell-free supernatant of B. licheniformis CFR1 was able to degrade AFB1 efficiently than the cell lysate. The degradation of AFB1 was examined using High-Performance Thin Layer Chromatography (HPTLC), High-Performance Liquid Chromatography (HPLC) and Electron spray ionization-Mass Spectrometry (ESI-MS). The optimal temperature, time, and pH of the medium for the maximum degradation of Aflatoxin B1 were found to be 37 °C, 24 h and 7, respectively. Furthermore, Ames test for mutagenicity showed that when treated with B. licheniformis CFR1 extracellular fraction coincided with the loss of Aflatoxin B1 mutagenicity. To the best of our knowledge, this is the first study that shows more than 90% degradation of AFB1 by B. licheniformis. Thus, B. licheniformis CFR1 might be an excellent candidate for bioremediation and detoxification of Aflatoxin B1 from both field and food matrices.

Histopathological and biochemical effects of cyanobacterial cells containing microcystin‐LR on Tilapia fish

AbstractBlooms of Microcystis aeruginosa, commonly observed in many lakes of Tamil Nadu, produce the cyanobacterial toxin Microcystin, which has tumor promoting property in fish. Strains of Microcystis aeruginosa species have the same morphology but may vary in their toxicity. In the present study, Microcystin produced by Microcystis aeruginosa from Thenneri lake in Kancheepuram district of Tamil Nadu, was isolated and characterized by high‐performance liquid chromatography and electron spray ionization mass spectroscopy. Based on spectroscopic results the toxin was identified as Microcystin‐LR. Toxicogenicity was evident from the alteration in the activity of antioxidant enzymes [Glutathione S‐transferase and Catalase] and increase of protein and lipid peroxidation contents in Oreochromis niloticus, a fresh water fish species, after controlled exposure to Microcystis aeruginosa cells. Toxicity was further confirmed by histopathological changes in gill, liver and intestine of exposed fish.

Assessment of a diketopiperazine, cyclo(Trp-Phe) from Streptomyces griseoplanus SAI-25 against cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Microorganisms produce a range of metabolites with varying pest control properties. With this concept, we earlier identified 15 Streptomyces spp. strains with insecticidal activity against Helicoverpa armigera (Hubner), Spodoptera litura (Fabricius), and Chilo partellus (Swinhoe). In recent studies, we evaluated an insecticidal compound purified from the extracellular extract of S. griseoplanus SAI-25 by bioactivity-guided fractionation against H. armigera. Spectral studies by infrared (IR), nuclear magnetic resonance (NMR), and electron spray ionization mass spectroscopy (ESI-MS) confirmed that the purified compound was cyclo(Trp-Phe) of the diketopiperazines class. Cyclo(Trp-Phe) exhibited antifeedant (70 %), larvicidal (67 %), and pupicidal (59 %) action against H. armigera in a dose-dependent manner. The lethal dose for 50 % of the group (LD50) and LD90 values for larvicidal effect were 619 and 2750 ppm, respectively. In addition, the purified compound prolonged larval (10.3–11.1 days) and pupal (10.9–11.8 days) periods compared with the untreated control (larval duration 9.8 days, pupal duration 10.6 days). This is the first report on the presence and biological activity of cyclo(Trp-Phe) isolated from the genus Streptomyces.

Conjugation of Ciprofloxacin with Poly(2-oxazoline)s and Polyethylene Glycol via End Groups.

The antibiotic ciprofloxacin (CIP) was covalently attached to the chain end of poly(2-methyloxazoline) (PMOx), poly(2-ethyloxazoline) (PEtOx), and polyethylene glycol (PEG), and the antimicrobial activity of these conjugates was tested for Staphylococcus aureus, Streptococcus mutans, Escherichia coli, Pseudomonas aeruginosa, and Kleisella pneumoniae. Chemical structures of the conjugates were proven by (1)H NMR and electron spray ionization mass spectrometry. The direct coupling of PMOx and CIP resulted in low antimicrobial activity. The coupling via a spacer afforded molecular weight dependent activity with a molar minimal inhibitory concentration that is even higher than that of the pristine CIP. The antimicrobial activity of the conjugates increases in the order of PMOx < PEtOx < PEG. Conjugation of CIP and a quaternary ammonium compound via PMOx did not result in higher activity, indicating no satellite group or synergistic effect of the different biocidal end groups.