Biologically active compounds of semi-metals

Determining growth inhibition of Candida albicans biofilm on denture materials after application of an organoselenium-containing dental sealant

STATEMENT OF PROBLEM

Denture stomatitis is a chronic inflammatory condition caused by the formation of Candida albicans biofilm on denture bases. It is associated with aggravating intraoral pain, itching, and burning sensations. It can also potentiate cardiovascular diseases and aspiration pneumonia. The problem has thus far eluded efficient, toxic-free, and cost-effective solutions.

PURPOSE

The purpose of this in vitro study was to investigate the effectiveness of organoselenium to inhibit the formation of C. albicans biofilm on the surface of acrylic resin denture base materials when it is either incorporated into the acrylic resin material or coated on the denture surface as a light-polymerized surface sealant.

MATERIAL AND METHODS

Sixty heat-polymerized polymethyl methacrylate disks were fabricated and assigned to 4 groups (n=15): disks coated with a light-polymerized organoselenium-containing enamel surface sealant (DenteShield), disks impregnated with 0.5% organoselenium (0.5% selenium), disks impregnated with 1% organoselenium (1% selenium), and disks without organoselenium (control). C. albicans biofilm was grown on each disk which had been placed in a well of the microtiter plate containing 1-mL brain heart infusion broth inoculated with C. albicans. The plates were incubated aerobically at 37 °C for 48 hours. A confocal laser scanning microscope was used to determine the biofilm thickness, biomass, and live/dead cell ratio. Biofilm morphology was examined with scanning electron microscopy, whereas microbial viability was quantified by the spread plate method. The data were analyzed by using ANOVA and Tukey-Kramer multiple comparisons (α=.05).

RESULTS

The microbial viability, biofilm thickness, biofilm biomass, and live/dead cell ratio were lower (P<.001) on disks in the test groups (DenteShield, 0.5% selenium, 1% selenium) when compared with the control group, with these variables being lowest in the 0.5% selenium and 1% selenium groups. The 0.5% selenium and 1% selenium groups did not differ significantly from each other in any of the variables (P>.05). Scanning electron microscope images showed inhibition of both biofilm growth and yeast to hyphae transition in the DenteShield, 0.5% selenium, and 1% selenium groups, with visible disruption of the biofilm morphology.

CONCLUSIONS

The present study demonstrated that organoselenium, whether incorporated into or coated on the surface of an acrylic resin denture base material, has the potential to inhibit Candida albicans biofilm growth on denture surfaces and as such can be clinically useful for the prevention of denture stomatitis.

The Chemotherapeutic Potentials of Compounds Isolated from the Plant, Marine, Fungus, and Microorganism: Their Mechanism of Action and Prospects

Research on natural products mainly focuses on developing a suitable drug to treat human disease. There has been a sharp increase in the development of drugs from natural products. Most of the drugs that are available are from the terrestrial origin. Marine natural products are less explored. Oceans are considered as a vast ecosystem with a wide variety of living organisms and natural products that are unexplored. Large numbers of antitumor drugs are from natural sources such as plants, marine, and microorganisms. 80% new chemical entities that were launched over the past 60 decades were from a natural source. In this article, the anticancer potential from the natural source such as plants, fungi, microorganisms, marine, and endophytes has been reviewed. Emphasis is given on the compound from the marine, plant, and of bacterial origin. Finally, we consider the future and how we might achieve better sustainability to alleviate human cancer suffering while having fewer side effects, more efficacies, and causing less harm than the present treatments.

Functions of elements in soil microorganisms

The soil microbial community fulfils various functions, such as nutrient cycling and carbon (C) sequestration, therefore contributing to maintenance of soil fertility and mitigation of global warming. In this context, a major focus of research has been on C, nitrogen (N) and phosphorus (P) cycling. However, from aquatic and other environments, it is well known that other elements beyond C, N, and P are essential for microbial functioning. Nonetheless, for soil microorganisms this knowledge has not yet been synthesised. To gain a better mechanistic understanding of microbial processes in soil systems, we aimed at summarising the current knowledge on the function of a range of essential or beneficial elements, which may affect the efficiency of microbial processes in soil. This knowledge is discussed in the context of microbial driven nutrient and C cycling. Our findings may support future investigations and data evaluation, where other elements than C, N, and P affect microbial processes.

Boron in Prebiological Evolution

Boron(III), as borate (or boric acid), mediates the synthesis of ribose, ribonucleosides, and ribonucleotides. These reactions are carried out under moderate temperatures (typically 70-95 °C) with organic molecules (or their derivatives) detected in interstellar space and inorganic ions found in minerals on Earth (and could occur during early stages of prebiotic evolution). Research in this century suggests that borate was a relevant prebiological reagent, thus reinforcing the RNA world hypothesis as an explanation for the origin of life. Herein, these developments on prebiological chemistry related to boron species are reviewed.

Sodium Tetraphenylborate Displays Selective Bactericidal Activity against Neisseria meningitidis and N. gonorrhoeae and Is Effective at Reducing Bacterial Infection Load

Neisseria meningitidis and Neisseria gonorrhoeae, two highly related species that might have emerged from a common commensal ancestor, constitute major human threats. Vaccines are available to prevent N. meningitidis infection, whereas there are only a limited number of antibiotics available for N. gonorrhoeae Unfortunately, some strains of these species are rapidly evolving and capable of escaping human interventions. Thus, it is now urgent to develop new avenues to fight these bacteria. This study reports that a boron-based salt, sodium tetraphenylborate (NaBPh₄), displays high bactericidal activity and remarkable specificity against N. meningitidis and N. gonorrhoeae Other closely related commensal species such as Neisseria lactamica, which is found in the normal flora of healthy individuals, were found to be less affected even at 5-fold higher doses of NaBPh₄ This specificity was further observed when much lower sensitivity was found for more distant Neisseriaceae species (such as Neisseria elongata or Kingella oralis) and completely unrelated species. Significant boron uptake by N. meningitidis cells was observed after incubation with 5 μM NaBPh₄, as measured by inductively coupled plasma mass spectrometry, suggesting that this drug candidate's target(s) could be located intracellularly or within the cell envelope. Furthermore, mutants with slightly decreased susceptibility displayed alterations in genes coding for cell envelope elements, which reduced their virulence in an animal model of infection. Finally, a single dose of NaBPh₄ resulted in a significant reduction in bacterial burden in a mouse model of N. meningitidis bacteremia. Although numerous boron-containing species were previously reported for their complex biological activities, the observation of this narrow selectivity is unprecedented and of potential importance from a therapeutic standpoint.

Potent Inhibition of Mandelate Racemase by Boronic Acids: Boron as a Mimic of a Carbon Acid Center

Boronic acids have been successfully employed as inhibitors of hydrolytic enzymes. Typically, an enzymatic nucleophile catalyzing hydrolysis adds to the electrophilic boron atom forming a tetrahedral species that mimics the intermediate(s)/transition state(s) for the hydrolysis reaction. We show that para-substituted phenylboronic acids (PBAs) are potent competitive inhibitors of mandelate racemase (MR), an enzyme that catalyzes a 1,1-proton transfer rather than a hydrolysis reaction. The K_i value for PBA was 1.8 ± 0.1 μM, and p-Cl-PBA exhibited the most potent inhibition (K_i = 81 ± 4 nM), exceeding the binding affinity of the substrate by ∼4 orders of magnitude. Isothermal titration calorimetric studies with the wild-type, K166M, and H297N MR variants indicated that, of the two Brønsted acid-base catalysts Lys 166 and His 297, the former made the greater contribution to inhibitor binding. The X-ray crystal structure of the MR·PBA complex revealed the presence of multiple H-bonds between the boronic acid hydroxyl groups and the side chains of active site residues, as well as formation of a His 297 N^ε2-B dative bond. The dramatic upfield change in chemical shift of 27.2 ppm in the solution-phase ¹¹B nuclear magnetic resonance spectrum accompanying binding of PBA by MR was consistent with an sp³-hybridized boron, which was also supported by density-functional theory calculations. These unprecedented findings suggest that, beyond substituting boron at carbon centers participating in hydrolysis reactions, substitution of boron at the acidic carbon center of a substrate furnishes a new approach for generating inhibitors of enzymes catalyzing the deprotonation of carbon acid substrates.

The use of isothermal titration calorimetry to unravel chemotactic signalling mechanisms

Chemotaxis is based on the action of chemosensory pathways and is typically initiated by the recognition of chemoeffectors at chemoreceptor ligand-binding domains (LBD). Chemosensory signalling is highly complex; aspect that is not only reflected in the intricate interaction between many signalling proteins but also in the fact that bacteria frequently possess multiple chemosensory pathways and often a large number of chemoreceptors, which are mostly of unknown function. We review here the usefulness of isothermal titration calorimetry (ITC) to study this complexity. ITC is the gold standard for studying binding processes due to its precision and sensitivity, as well as its capability to determine simultaneously the association equilibrium constant, enthalpy change and stoichiometry of binding. There is now evidence that members of all major LBD families can be produced as individual recombinant proteins that maintain their ligand-binding properties. High-throughput screening of these proteins using thermal shift assays offer interesting initial information on chemoreceptor ligands, providing the basis for microcalorimetric analyses and microbiological experimentation. ITC has permitted the identification and characterization of many chemoreceptors with novel specificities. This ITC-based approach can also be used to identify signal molecules that stimulate members of other families of sensor proteins.

Synthesis of novel tellurides bearing benzensulfonamide moiety as carbonic anhydrase inhibitors with antitumor activity

We have synthetized a novel series of β-hydroxy tellurides bearing the benzenesulfonamide group as potent inhibitors of carbonic anhydrase enzymes. In a one pot procedure, we discovered both the ring opening reaction of the three-membered ring and the cleavage of the sulfonamide protecting moiety at the same time. Moreover, the first X-ray co-crystallographic structure of a β-hydroxy telluride derivative with hCA II is reported. The potent effects of these compounds against the tumor-associated hCA IX with low nanomolar constant inhibition values give the possibility to evaluate their activity in vitro using a breast cancer cell line (MDA-MB-231). Compounds 7e and 7g induced significant toxic effects against tumor cells after 48 h incubation in normoxic conditions killing over 50% of tumor cells at 3 μM, but their efficacy decreased in hypoxic conditions reaching the 50% of the tumor cell viability only at 30 μM. These unusual features make them interesting lead compounds to act as antitumor agents, not only as Carbonic Anhydrase IX inhibitors, but reasonably in different pathways, where hCA IX is not overexpressed.

Continuous flow electrosorption-microbial fuel cell system for efficient removal of oxytetracycline without external electrical supply

The removal of antibiotics from wastewater has attracted much attention. In this research, an intimately coupled autarkical electrosorption (ES)-microbial fuel cell (MFC) system was developed for real-time removal of the antibiotic oxytetracycline (OTC) from wastewater. The removal efficiency was founded to be up to 98.8% at an OTC concentration of 2 mg/L with 3 g/L sodium acetate (NaAC) as co-substrate and 3 MFCs as power supply. The removal efficiencies increased in the ES unit and decreased in the MFC unit with increasing treating time. The adsorption of OTC on activated carbon fibers (ACFs) in the ES unit proceeds via chemical adsorption resulting from electrostatic attraction and cation exchange. The OTC degradation pathways in the MFC unit were proposed by identifying the intermediates with HPLC-MS/MS. The ACFs in the ES unit were proven to be recyclable and the coupled ES-MFC system is applicable for the removal of antibiotics from wastewater.

Selenium-enriched Coriolus versicolor mushroom biomass: potential novel food supplement with improved selenium bioavailability

BACKGROUND

The ability of Coriolus versicolor medicinal mushroom to accumulate and transform selenium from selenourea and sodium selenite into an organic form - l-selenomethionine - during growth in liquid medium is examined in this paper. Additionally, the impact of supplementation on biological activity of the selenated mushroom methanol extracts, as well as their chemical composition, is studied.

RESULTS

Selenium accumulation was more efficient with sodium selenite application, but biomass yield was significantly lower (1.89 g DW L^-1 ) compared to samples enriched with selenourea (4.48 g DW L^-1 ). Mushroom sample obtained after growing in liquid medium with selenourea had significantly higher l-selenomethionine content compared to the sample grown in medium with sodium selenite. Selenium-enriched methanol extracts of C. versicolor mushroom showed improved antimicrobial and antioxidant activities compared to non-enriched extract.

CONCLUSION

Our results suggest that C. versicolor mushroom cultivated in liquid culture enriched with selenourea can be used for the production of novel food supplements with improved selenium bioavailability. More than 30% of total accumulated selenium from selenourea is transformed into l-selenomethionine. Differences in biological activity of methanol extracts can be explained not only by different selenium content but also by the differences in chemical composition of extracts. © 2019 Society of Chemical Industry.

The Fructoborates: Part of a Family of Naturally Occurring Sugar-Borate Complexes-Biochemistry, Physiology, and Impact on Human Health: a Review

Sugar-borates (SBs) are mono- or di-sugar-borate esters (SBEs) comprised of one or two monosaccharide molecules linked to a boron (B) atom. SBEs occur naturally in commonly consumed herbs, vegetables, fruits, seeds, and nuts and, other than greatly varying levels of B found in local drinking water, are the primary natural dietary sources of B-containing molecules in humans. To date, the most studied SBE is calcium fructoborate (CaFB). CaFB represents an important example of how organic B-containing molecules are significantly distinct from their inorganic counterparts. During these past two decades, CaFB has been researched for its physical and biochemical characteristics, safety, and clinical outcomes. Results of these researches are presented and discussed herein. CaFB has been characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), high-performance thin-layer chromatography (HPTLC), nuclear magnetic resonance (NMR), liquid chromatography-multistage accurate mass spectrometry (LC-MSn), X-ray diffraction (XRD), Raman spectroscopy, and inductively coupled plasma (ICP) in non-biological and biological specimens. Potential health benefits of CaFB have been clinically investigated in pilot and efficacy studies demonstrating (i) significant reductions in knee discomfort and improved flexibility within 7, 14, and 90 days and (ii) significant effect on blood levels of inflammatory, cardiovascular, and other biomarkers. These studies support the use of CaFB as a dietary supplement for the management of joint discomfort. CaFB is presented here in order to illustrate how physiological benefits are imparted by distinct organic boron-containing molecules rather than solely by the element B itself. Considering recent National Health and Nutrition Examination Survey (NHANES) data reporting increases in age-related joint pain and an increasing elderly demographic, SBEs offer potential for safe, natural, and effective management of joint discomfort and improved mobility in human and animal health applications. Several of these studies may also open new opportunities for use of SBEs for health benefits beyond joint health.

Silyl radical initiated radical cascade addition/cyclization: synthesis of silyl functionalized 4H-pyrido[4,3,2-gh]phenanthridin-5(6H)-ones

A cyclization cascade initiated by the addition of a silyl radical to an electron-deficient carbon-carbon double bond of N-arylacrylamides, followed by intramolecular cyano group insertion and homolytic aromatic substitution has been reported. In the presence of di-lauroyl peroxide (LPO), under metal-free conditions, several readily available hydrosilanes were successfully used as the source of silyl radicals and a series of silyl functionalized 4H-pyrido[4,3,2-gh]phenanthridin-5(6H)-ones were obtained in moderate to good yields.

Potential Phytopharmacy and Food Applications of Capsicum spp.: A Comprehensive Review

Capsicum genus (Solanaceae) is native to the Americas. Today, it is an important agricultural crop cultivated around the world, not only due to its economic importance, but also for the nutritional value of the fruits. Among their phytochemical constituents, capsaicinoids are characteristic and responsible of the pungency of sharp-tasting cultivars. Moreover, Capsicum and capsaicinoids (mainly, capsaicin) have been largely studied because of their health benefits. Thus, this study reviews the scientific knowledge about Capsicum spp. and their phytochemicals against cancer, diabetes, gastrointestinal diseases, pain, and metabolic syndrome, as well as their antioxidant and antimicrobial activity. These bioactivities can be the basis of the formulation of functional ingredients and natural preservatives containing Capsicum extracts or isolated compounds.

Activation of the NLRP3 Inflammasome by Hyaboron, a New Asymmetric Boron-Containing Macrodiolide from the Myxobacterium Hyalangium minutum

A Natural Compound Library containing myxobacterial secondary metabolites was screened in murine macrophages for novel activators of IL-1β maturation and secretion. The most potent of three hits in total was a so far undescribed metabolite, which was identified from the myxobacterium Hyalangium minutum strain Hym3. While the planar structure of 1 was elucidated by high resolution mass spectrometry and NMR data yielding an asymmetric boron containing a macrodiolide core structure, its relative stereochemistry of all 20 stereocenters of the 42-membered ring was assigned by rotating frame Overhause effect spectroscopy correlations, ¹H,¹H, and ¹H,¹³C coupling constants, and by comparison of ¹³C chemical shifts to those of the structurally related metabolites tartrolon B-D. The absolute stereochemistry was subsequently assigned by Mosher's and Marfey's methods. Further functional studies revealed that hyaboron and other boronated natural compounds resulted in NLRP3 inflammasome dependent IL-1β maturation, which is most likely due to their ability to act as potassium ionophores. Moreover, besides its inflammasome-stimulatory activity in human and mouse cells, hyaboron (1) showed additional diverse biological activities, including antibacterial and antiparasitic effects.

The importance of boron in biological systems

Boron is an essential element for plants and probably essential for human and animal health. Boron has a broad range of physiological effects on biological systems at low concentrations, whereas it is toxic to at high concentrations. Eventhough there are many studies on boron's biological effects and toxicity, more information is needed to understand the mechanisms of its action. The aim of the current work is to review boron's function, transport and toxicity in different biological systems.

Identification of boric acid as a novel chemoattractant and elucidation of its chemoreceptor in Ralstonia pseudosolanacearum Ps29

Chemotaxis enables bacteria to move toward more favorable environmental conditions. We observed chemotaxis toward boric acid by Ralstonia pseudosolanacearum Ps29. At higher concentrations, the chemotactic response of R. pseudosolanacearum toward boric acid was comparable to or higher than that toward L-malate, indicating that boric acid is a strong attractant for R. pseudosolanacearum. Chemotaxis assays under different pH conditions suggested that R. pseudosolanacearum recognizes B(OH)₃ (or B(OH₃) + B(OH)₄⁻) but not B(OH)₄⁻ alone. Our previous study revealed that R. pseudosolanacearum Ps29 harbors homologs of all 22R. pseudosolanacearum GMI1000 mcp genes. Screening of 22 mcp single-deletion mutants identified the RS_RS17100 homolog as the boric acid chemoreceptor, which was designated McpB. The McpB ligand-binding domain (LBD) was purified in order to characterize its binding to boric acid. Using isothermal titration calorimetry, we demonstrated that boric acid binds directly to the McpB LBD with a K_D (dissociation constant) of 5.4 µM. Analytical ultracentrifugation studies revealed that the McpB LBD is present as a dimer that recognizes one boric acid molecule.

Arsenic-Redox Transformation and Plant Growth Promotion by Purple Nonsulfur Bacteria Rhodopseudomonas palustris CS2 and Rhodopseudomonas faecalis SS5

Arsenic (As) is a well-known toxic metalloid found naturally and released by different industries, especially in developing countries. Purple nonsulfur bacteria (PNSB) are known for wastewater treatment and plant growth promoting abilities. As-resistant PNSB were isolated from a fish pond. Based on As-resistance and plant growth promoting attributes, 2 isolates CS2 and SS5 were selected and identified as Rhodopseudomonas palustris and Rhodopseudomonas faecalis, respectively, through 16S rRNA gene sequencing. Maximum As(V) resistance shown by R. faecalis SS5 and R. palustris CS2 was up to 150 and 100 mM, respectively. R. palustris CS2 showed highest As(V) reduction up to 62.9% (6.29 ± 0.24 mM), while R. faecalis SS5 showed maximum As(III) oxidation up to 96% (4.8 ± 0.32 mM), respectively. Highest auxin production was observed by R. palustris CS2 and R. faecalis SS, up to 77.18 ± 3.7 and 76.67 ± 2.8 μg mL^-1, respectively. Effects of these PNSB were tested on the growth of Vigna mungo plants. A statistically significant increase in growth was observed in plants inoculated with isolates compared to uninoculated plants, both in presence and in absence of As. R. palustris CS2 treated plants showed 17% (28.1 ± 0.87 cm) increase in shoot length and 21.7% (7.07 ± 0.42 cm) increase in root length, whereas R. faecalis SS5 treated plants showed 12.8% (27.09 ± 0.81 cm) increase in shoot length and 18.8% (6.9 ± 0.34 cm) increase in root length as compared to the control plants. In presence of As, R. palustris CS2 increased shoot length up to 26.3% (21.0 ± 1.1 cm), while root length increased up to 31.3% (5.3 ± 0.4 cm), whereas R. faecalis SS5 inoculated plants showed 25% (20.7 ± 1.4 cm) increase in shoot length and 33.3% (5.4 ± 0.65 cm) increase in root length as compared to the control plants. Bacteria with such diverse abilities could be ideal for plant growth promotion in As-contaminated sites.

Morin P, Westcott SA. Synthesis, characterization, and anticancer properties of iminophosphineplatinum(II) complexes containing boronate esters

Three new iminophosphines containing pinacol-derived boronate esters have been prepared and ligated to dichloridoplatinum(II) fragments. All compounds have been characterized fully, including an X-ray diffraction study carried out for the platinum complex 8, which is derived from 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline. These three new platinum complexes, along with the non-boron containing control, have been examined for their initial cytotoxic properties against two glioma cell lines using the MTT method.

Study of Fluorescent Imaging of Se (IV) in Living Cells Using a Turn-on Fluorescent Probe Based on a Rhodamine Spirolactame Derivative

A highly selective fluorescent probe 2-(2-(2-aminoethylamino)ethyl)-3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one (ABDO) for Se (IV) had been synthesized in our earlier report. In this study, this fluorescent sensor is applied on analysis fluorescent imaging of Se (IV) in Hela cells. The experiment conditions, such as the MTT assay, different concentration of saline, incubated time of Hela cells with ABDO and Se (IV), and intracellular action position of Se (IV), are investigated. Through a series of experiments, the fluorescent image of Se (IV) in Hela cells can be observed when the cells cultured by 2 μM ABDO and 2 μM Se (IV) for 210 min. And the intracellular action position of Se (IV) is verified after the co-localization experiments are done. It is mitochondria. These experimental results show that ABDO will be an eagerly anticipated sensor for fluorescent imaging analysis of selenium ion in living cells. Besides, we also can use the complexes of ABDO-Se to observe morphology and distribution of mitochondria in cells like JG-B.

Silicon as Versatile Player in Plant and Human Biology: Overlooked and Poorly Understood

Silicon (Si) serves as bioactive beneficial element. Si is highly abundant in soil, and occurs ubiquitously in all organisms including plants and humans. During the last three decades, nutritional significance of Si for plant and human health has received increasing attention. Plant Si plays a pivotal role in growth and development, and this beneficial effect depends usually on accumulation in plant tissues, which are then protected from various forms of biotic and abiotic stresses. Likewise, human exposure to Si imparts health benefits and essentially occurs through plant-derived food products. Si bioavailability in human diet, e.g., strengthens bones and improves immune response, as well as neuronal and connective tissue health. Despite this empiric knowledge, the essentiality of Si still remains enigmatic. Thus the link between Si availability for plant development and its profound implication for human welfare should receive attention. This review aims to provide a broad perspective on Si as important element for plant and human nutrition and to define research fields for interdisciplinary research.

Update on the possible nutritional importance of silicon

Convincing evidence that silicon is a bioactive beneficial trace element continues to accumulate. The evidence, which has come from human, animal, and in vitro studies performed by several laboratories, indicate that silicon in nutritional and supra nutritional amounts promotes bone and connective tissue health, may have a modulating effect on the immune or inflammatory response, and has been associated with mental health. A plausible mechanism of action for the beneficial effects of silicon is the binding of hydroxyl groups of polyols such that it influences the formation and/or utilization of glycosaminoglycans, mucopolysaccharides, and collagen in connective tissue and bone. In addition, silicon may affect the absorption, retention or action of other mineral elements (e.g., aluminum, copper, magnesium). Based on findings from both animal and human experiments, an intake of silicon of near 25mg/d would be a reasonable suggestion for an adequate intake that would assure its nutritional benefits. Increased intakes of silicon through consuming unrefined grains, certain vegetables, and beverages and cereals made from grains should be recognized as a reasonable dietary recommendation.

The elemental composition of demospongiae from the Red Sea, Gulf of Aqaba

Trace elements are vital for the growth and development of all organisms. Little is known about the elemental content and trace metal biology of Red Sea demosponges. This study establishes an initial database of sponge elemental content. It provides the necessary foundation for further research of the mechanisms used by sponges to regulate the uptake, accumulation, and storage of metals. The metal content of 16 common sponge species was determined using ICP measurements. A combination of statistical methods was used to determine the correlations between the metals and detect species with significantly high or low concentrations of these metals. Bioaccumulation factors were calculated to compare sponge metal content to local sediment. Theonella swinhoei contained an extremely high concentration of arsenic and barium, much higher (at least 200 times) than all other species and local sediment. Hyrtios erecta had significantly higher concentration of Al, Cr, Fe, Mn, Ti and V than all other species. This is due to sediment accumulation and inclusion in the skeleton fibers of this sponge species. Suberites clavatus was found to contain significantly higher concentration of Cd, Co, Ni and Zn than all other species and local sediment, indicating active accumulation of these metals. It also has the second highest Fe concentration, but without the comparably high concentrations of Al, Mn and Ti that are evident in H. erecta and in local sediment. These differences indicate active uptake and accumulation of Fe in S. clavatus, this was also noted in Niphates rowi. A significantly higher B concentration was found in Crella cyatophora compared to all other species. These results indicate specific roles of trace elements in certain sponge species that deserve further analysis. They also serve as a baseline to monitor the effects of anthropogenic disturbances on Eilat's coral reefs.

Pharmacological importance of an ethnobotanical plant: Capsicum annuum L

Capsicum annuum L., a fruit plant from tropical and subtropical regions, contains a range of essential nutrients and bioactive compounds which are known to exhibit a range of bioactivities including free radical scavenging (antioxidant), antimicrobial, antiviral, anti-inflammatory and anticancer. This review aims to give a comprehensive overview of the literature published on pharmacological behaviours of C. annuum L.

Boron chemicals in diagnosis and therapeutics

Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade(®)), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin's lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans.

Evaluating the antioxidative activity of diselenide containing compounds in human blood

This study was designed to determine and compare the antioxidant effects of synthetic organoselenium compounds. In experimental trials three different diselenides were used: bis(2-hydroxyphenyl) diselenide, bis{[2-(4-hydroxybenzyl)imino]phenyl} diselenide and bis[2-(4-methylphenylsulfonylamino)phenyl] diselenide. The compounds were screened for antioxidant activities in human blood under oxidation stress conditions. Oxidative stress was induced in vitro in human blood platelet samples and in plasma by 0.1 mM peroxynitrite (ONOO(-)) or by Fe(2+). In experimental trials the levels of chosen oxidative stress markers (TBARS, O2(-), and protein carbonyl groups) were significantly decreased by the action of the tested compounds. The antioxidative properties and the changes in proteins and lipids in the presence of new synthesized selenoorganic compounds were studied in vitro and compared with activity of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one)--a classical antioxidant, well known as the most important glutathione peroxidase mimetic agent. Our results indicate that the tested diselenides have distinctly protective effects against oxidative alterations of biomolecules caused by ONOO(-) and Fe(2+) in blood platelets and in plasma. Therefore it seems that not only ebselen with a wide spectrum of therapeutic actions but also other organoselenium compounds can be considered in the future as active pharmacological agents.

Oxidant balance in brain of rats receiving different compounds of selenium

The influence of two organic selenocompounds and sodium selenite on oxidant processes in rat brain tissue was investigated. The study was performed on male Wistar rats. The animals were divided into four groups: I—control; II—administered with sodium selenite; III—provided with selenoorganic compound A of chain structure 4-(o-tolyl-)-selenosemicarbazide of 2-chlorobenzoic acid and IV—provided with selenoorganic compound B of ring structure 3-(2-chlorobenzoylamino-)-2-(o-tolylimino-)-4-methyl-4-selenazoline. Rats were treated by stomach tube at a dose of 5 × 10⁻⁴ mg of selenium/g of b.w. once a day for a period of 10 days. In brain homogenates total antioxidant status (TAS), activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), concentrations of ascorbic acid (AA) and reduced glutathione (GSH) as well as concentration of malonyl dialdehyde (MDA) were determined. TAS was insignificantly diminished in all selenium-supplemented groups versus control. SOD was not significantly influenced by administration of selenium. GPx was markedly decreased in group III versus control, whereas increased in group IV versus control and group III. Selenosemicarbazide depleted AA in well-marked way versus group II. GSH was significantly depressed in group III versus both control and group II and diminished in group IV versus group II. MDA was significantly decreased in group III versus both control and group II, whereas in group IV increased versus group III. As selenazoline A did not decrease elements of antioxidant barrier and increased GPx activity, it seems to be a promising agent for future studies concerning its possible application as a selenium supplement.

Antibacterial evaluation of novel organoarsenic compounds by the microcalorimetric method

Antibacterial activities of novel organoarsenic compounds As(III)-containing Schiff bases on Escherichia coli (CCTCCAB91112) were investigated by microcalorimetry in this study. The experimental result showed that the arsenic(III)-containing Schiff bases at micromolar concentration exhibit strong inhibition on the E. coli. Specifically, the growth rate constant k decreased, and the generation time t G and the inhibitory ratio I (percentage) increased with the increased dose of the arsenicals as inhibitors. All of the arsenicals display the feature of considerable lag phase inhibition on the cell growth. The compound 4-(4-bromobenzaliminyl)phenylarsenoxide makes the lag phase of E. coli cell growth cycles to reach 650 min at 5 μmol/L. The compounds with donating electron groups at aromatic ring B have lower IC50 to present higher antibacterial activity. The compound 4-(4-hydroxyl-3-methoxylbenzaliminyl)phenylarsenoxide has the lowest IC50 (1.82 μmol/L) to show the strongest antibacterial activity among them.

Boron as a platform for new drug design

INTRODUCTION

Boron lies on the borderline between metals and non-metals in the periodic table. As such, it possesses peculiarities which render it suitable for a variety of applications in chemistry, technology and medicine. However, boron's peculiarities have been exploited only partially so far.

AREAS COVERED

In this review, the authors highlight selected areas of research which have witnessed new uses of boron compounds in recent times. The examples reported illustrate how difficulties in the synthesis and physicochemical characterization of boronated molecules, encountered in past years, can be overcome with positive effects in different fields.

EXPERT OPINION

Many potentialities of boron-based systems reside in the peculiar properties of both boron atoms (the ability to replace carbon atoms, electron deficiency) and of boronated compounds (hydrophobicity, lipophilicity, versatile stereochemistry). Taken in conjunction, these properties can provide innovative drugs. The authors highlight the need to further investigate the assembly of boronated compounds, in terms of drug design, since the mechanisms required to obtain supramolecular structures may be unconventional compared with the more standard molecules used. Furthermore, the authors propose that computational methods are a valuable tool for assessing the role of multicenter, quasi-aromatic bonds and its peculiar geometries.

Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry

Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9 Sargassum fulvellum were analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g(-1). Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography-ultraviolet photo-oxidation-hydride generation atomic-fluorescence spectrometry (HPLC-(UV)-HG-AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g(-1), whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g(-1)). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g(-1)) and generally high arsenate (As(V)) concentrations (up to 77 μg g(-1)) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products.

Is boron a prebiotic element? A mini-review of the essentiality of boron for the appearance of life on earth

Boron is probably a prebiotic element with special importance in the so-called "sugars world". Boron is not present on Earth in its elemental form. It is found only in compounds, e.g., borax, boric acid, kernite, ulexite, colemanite and other borates. Volcanic spring waters sometimes contain boron-based acids (e.g., boric, metaboric, tetraboric and pyroboric acid). Borates influence the formation of ribofuranose from formaldehyde that feeds the "prebiotic metabolic cycle". The importance of boron in the living world is strongly related to its implications in the prebiotic origins of genetic material; consequently, we believe that throughout the evolution of life, the primary role of boron has been to provide thermal and chemical stability in hostile environments. The complexation of boric acid and borates with organic cis-diols remains the most probable chemical mechanism for the role of this element in the evolution of the living world. Because borates can stabilize ribose and form borate ester nucleotides, boron may have provided an essential contribution to the "pre-RNA world".

Therapeutic potential of selenium and tellurium compounds: opportunities yet unrealised

Despite being disparaged for their malodorous and toxic demeanour, compounds of selenium, a bio-essential element, and tellurium, offer possibilities as therapeutic agents. Herein, their potential use as drugs, for example, as anti-viral, anti-microbial, anti-inflammatory agents, etc., will be surveyed along with a summary of the established biological functions of selenium. The natural biological functions of tellurium remain to be discovered.

Antifungal Activity and Possible Mode of Action of Borate Against Colletotrichum gloeosporioides on Mango

The effect of potassium tetraborate on germination of conidia of Colletotrichum gloeosporioides, and postharvest rot of mango were studied. An application of K₂B₄O₇ to mango trees at flowering increased fruit set and decreased the incidence of anthracnose on harvested fruit. The effects of borate on the germination, nuclear division, endocytosis, and ultrastructure of conidia of C. gloeosporioides were studied using light, confocal, and transmission electron microscopy. The results showed that borate inhibited germination and germ tube elongation, delayed nuclear division, and impaired endocytosis of C. gloeosporioides conidia. Ultrastructural abnormalities also occurred in conidia treated with borate, and these included an increase in numbers of vacuoles, cytoplasmic disintegration, mitochondria degradation, and plasmolysis. These results suggest that borate can serve as a potential alternative to synthetic fungicides for the control of the postharvest disease of mango fruit caused by C. gloeosporioides.