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The multivariate analytical approach based on LC/MS chemical constituent data differentiated the three chemical races of Laurencia nipponica, i.e., laurencin (1)-, laurallene (2)-, and prepacifenol-producing races, according to the first report of chemical races in the 1990s. The race-index compounds (1 and 2), prepacifenol structural isomer pacifenol (3), and another brominated compound laureatin (4), were isolated from each corresponding race. The compounds (1–4) were subjected to cytotoxicity and genotoxicity assays using the human lymphoblastoid TK6 cell line, as well as antifungal activity assays against Aspergillus niger and Penicillium citrinum. Among them, only 2 showed cytotoxicity against TK6 cells at concentrations of 5.0 and 10.0 μg mL−1. In genotoxicity assays, DNA migration and chromosome aberrations were observed in 2 at cytotoxic concentrations, suggesting that the compound's cytotoxicity was induced by genotoxic factors such as DNA and chromosome damage. In acridine orange (AO)/ethidium bromide (EB) staining, TK6 cells treated with 2 were stained with EB but not AO, implying that the compound's genotoxic effects caused necrotic cytotoxicity. None of the four compounds (1–4) showed fungicidal activity against A. niger and P. citrinum. Thus, the multivariate approach facilitates detection of races. Moreover, this study reveals new biological activity information about race-index compounds whose ecological roles have not yet been characterized. [ABSTRACT FROM AUTHOR]

The current study numerically evaluates the detonation inhibition effects of a range of halogenated compounds on hydrogen-air gaseous detonations. The halogenated compounds investigated in this research encompass halogen acids (HI, HBr, HCl, HF), halomethanes ( CH 3 I , CH 3 Br , CH 3 Cl , CH 3 F ), haloethenes ( C 2 H 3 I , C 2 H 3 Br , C 2 H 3 Cl , C 2 H 3 F ), haloethanes ( C 2 H 5 I , C 2 H 5 Br , C 2 H 5 Cl , C 2 H 5 F ), and complex halogenated compounds ( CF 3 I , CF 3 Br , CF 3 Cl , CF 4 ). The study employs a one-dimensional ZND model with detailed chemical kinetics to examine the impact on detonation propagation by adding these halogenated compounds to hydrogen-air mixtures. The effectiveness of these inhibitors is evaluated based on their capacity to increase the induction length, the amount of inhibitor needed to attenuate a detonation wave, and their influence on the detonability of the gaseous mixture under both lean and rich conditions. The results indicate that several halogenated compounds exhibit superior inhibition properties compared to Halon 1301 ( CF 3 Br ). Specifically, C 2 H 5 Br leads to the most significant increase in the induction length, with HBr and C 2 H 5 I following closely, particularly at 20,000 ppmv concentration levels. However, it is worth noting that the inhibition efficiency also varies depending on the concentration of the inhibitor added to the gaseous H 2 -air mixture. Moreover, based on retardant weight analysis, fluorinated compounds were found to be the most effective inhibitors, followed by chlorinated, brominated, and iodinated compounds across all categories of halogenated inhibitors. [ABSTRACT FROM AUTHOR]

Marine sponges are recognized as valuable sources of bioactive metabolites and renowned as petri dishes of the sea, providing specialized niches for many symbiotic microorganisms. Sponges of the family Dysideidae are well documented to be chemically talented, often containing high levels of polyhalogenated compounds, terpenoids, peptides, and other classes of bioactive small molecules. This group of tropical sponges hosts a high abundance of an uncultured filamentous cyanobacterium, Hormoscilla spongeliae Here, we report the comparative genomic analyses of two phylogenetically distinct Hormoscilla populations, which reveal shared deficiencies in essential pathways, hinting at possible reasons for their uncultivable status, as well as differing biosynthetic machinery for the production of specialized metabolites. One symbiont population contains clustered genes for expanded polybrominated diphenylether (PBDE) biosynthesis, while the other instead harbors a unique gene cluster for the biosynthesis of the dysinosin nonribosomal peptides. The hybrid sequencing and assembly approach utilized here allows, for the first time, a comprehensive look into the genomes of these elusive sponge symbionts.IMPORTANCE Natural products provide the inspiration for most clinical drugs. With the rise in antibiotic resistance, it is imperative to discover new sources of chemical diversity. Bacteria living in symbiosis with marine invertebrates have emerged as an untapped source of natural chemistry. While symbiotic bacteria are often recalcitrant to growth in the lab, advances in metagenomic sequencing and assembly now make it possible to access their genetic blueprint. A cell enrichment procedure, combined with a hybrid sequencing and assembly approach, enabled detailed genomic analysis of uncultivated cyanobacterial symbiont populations in two chemically rich tropical marine sponges. These population genomes reveal a wealth of secondary metabolism potential as well as possible reasons for historical difficulties in their cultivation.

Biofilm formation has been identified as one of the major pathways by which pathogens evade the effect of antimicrobial agents, leading to drug resistance in general. The imidazole ring provides a promising scaffold for the design of viable antimicrobial agents. In this work, halogenated benzyl derivatives of imidazole were synthesized and evaluated for antimicrobial and anti-biofilm activity. Molecular docking was used to analyse interactions between the compounds and the transcriptional regulator protein, LasR - a major protein that has downstream effect on biofilm formation in Pseudomonas aeruginosa. Results from the study revealed the marked potency of the halogenated compounds as antimicrobial agents. Antimicrobial susceptibility tests showed that the bromo- derivatives were very active against Gram-positive bacteria. The chloro- derivatives, on the other hand portrayed, a broad spectrum of antimicrobial activity. Notably, N-2-chlorobenzyl imidazole appeared to be the most potent antimicrobial agent with an MIC of 0.250 mg/mL against P. aeruginosa. Despite the relatively low antimicrobial effects displayed by the fluoro- derivatives, N-3-fluorobenzyl imidazole was identified to be a very good anti-biofilm agent with 5.3 µg/mL of the compound needed to inhibit biofilm formation by 50% (BIC50). Furthermore, all the compounds inhibited biofilms produced by Pseudomonas aeruginosa at sub-MIC concentrations. Predictions from molecular docking studies suggest that the compounds may not target the LasR protein in eliciting their anti-biofilm property.

The seaweed Asparagopsis armata has been shown to be a successful intervention to mitigate methane (CH 4) emissions from ruminants due to the content of halogenated components, including bromoform. Some groups have been exploring extracting or synthesizing bromoform to be used as a feed additive rather than using whole seaweed biomass. This study was conducted to understand the differences between whole A. armata biomass and bromoform in their ability to reduce CH 4 production when included in ruminant diets. A series of in vitro experiments were conducted, with a control group consisting of a 50 % hay:50 % concentrate. A. armata biomass supplementation levels of 0.25 and 0.50 %, containing 0.0037 and 0.0077 mg bromoform on a dry matter (DM) basis, respectively, were evaluated. Bromoform was evaluated at 0.0018, 0.0036, and 0.0073 mg. The two highest levels of bromoform were comparable to the bromoform content in the seaweed biomass. Adding A. armata biomass led to significant reductions in CH 4 yield (mL/g) of 62.5 and 95.6 %, respectively, without compromising in vitro fermentation characteristics. The addition of bromoform resulted in a decrease in the CH 4 yield (mL/g) by 7.6, 23.0, and 59.6 %, respectively. In conclusion, while bromoform led to a dose-dependent reduction in CH 4 production, A. armata has a greater effect at equivalent doses of bromoform, suggesting that the other components in the biomass, which were responsible for up to 40 % of the reduction, play a significant role in the anti-methanogenic efficiency of A. armata. • This study evaluated the differences in the anti-methanogenic potential of Asparagopsis armata biomass versus bromoform. • While bromoform was the strongest anti-methanogenic compound, the biomass was 36-40 % more powerful than bromoform alone. • At the tested levels, the biomass and bromoform had no negative impacts on in vitro rumen fermentation. • The role of bioactive compounds other than bromoform in Asparagopsis biomass is significant and should not be ignored. [ABSTRACT FROM AUTHOR]

[Display omitted] • The molecular structures of the neutral and cation 1,2-dichloropropane (C 3 H 6 Cl 2) have been studied. • Three stable conformations have been found for the isolated neutral molecule. • Five stable conformations have been found for the isolated molecular cation. • First ionization energy and IR spectra were calculated and compared to experimental data. A theoretical investigation on the molecular structures of the isolated 1,2-dichloropropane (C 3 H 6 Cl 2) neutral and its molecular cation was performed using high levels of density functional theory and ab initio methods. Three stable structural conformers have been found for the neutral molecule, with the Trans conformation being the most stable by about 5.8 kJ/mol on average in comparison with the (+) Gauche and (−) Gauche conformations. As for the molecular cation, five stable conformational structures have been determined with energy differences within about 25 kJ/mol, and with the (−) Near Cis conformer being the most stable cation species. The computed vibrational frequencies were compared with experimental values and the main IR spectral features assigned. The theoretical first adiabatic ionization energy of has been determined as 10.69 ± 0.05 eV, from the corresponding neutral and cation molecular energies, via ab initio composite methods, and is in good agreement with the experimental value from photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Natural products derived from marine microorganisms have been received great attention as a potential source of new compound entities for drug discovery. The unique marine environment brings us a large group of halogen‐containing natural products with abundant biological functionality and good drugability. Meanwhile, biosynthetically halogenated reactions are known as a significant strategy used to increase the pharmacological activities and pharmacokinetic properties of compounds. Given that a tremendous increase in the number of new halogenated compounds from marine microorganisms in the last five years, it is necessary to summarize these compounds with their diverse structures and promising bioactivities. In this review, we have summarized the chemistry, biosynthesis (related halogenases), and biological activity of a total of 316 naturally halogenated compounds from marine microorganisms covering the period of 2015 to May 2021. Those reviewed chlorinated and brominated compounds with the ratio of 9 : 1 were predominantly originated from 36 genera of fungi (62%) and 9 bacterial strains (38%) with cytotoxic, antibacterial, and enzyme inhibitory activities, structural types of which are polyketides (38%), alkaloids (27%), phenols (11%), and others. This review would provide a plenty variety of promising lead halogenated compounds for drug discovery and inspire the development of new pharmaceutical agents. [ABSTRACT FROM AUTHOR]

Dehalogenases are microbial enzyme catalysed the cleavage of carbon-halogen bond of halogenated organic compounds. It has potential use in the area of bio-technology such as bioremediation and chemical industry. Halogenated organic compounds can be found in the environment due to utili-zation in agriculture and industry, such as pesticides and herbicides. The presence of halogenated compound in the environment have been implicated on the health and natural ecosystem. Microbial dehalogenation is a significant method to tackle this problem. This review intends to briefly describe the microbial dehalogenases in relation to the environment where they are isolated. The basic information about dehalogenases in relation to dehalogenation mechanisms, classification, sources and the transportation of these pollutants into bacterial cytoplasm will be de-scribed. We also summarised readily available synthetic halogenated organic compounds in the environment.

Although the genus Asparagopsis includes only two taxonomically accepted species, the published literature is unanimous about the invasive nature of this genus in different regions of the globe, and about the availability of large amounts of biomass for which it is important to find a commercial application. This review shows that extracts from Asparagospsis species have already been evaluated for antioxidant, antibacterial, antifungal, antiviral, antifouling, cytotoxic, antimethanogenic and enzyme-inhibitory activity. However, the tables presented herein show, with few exceptions, that the activity level displayed is generally low when compared with positive controls. Studies involving pure compounds being identified in Asparagopsis species are rare. The chemical compositions of most of the evaluated extracts are unknown. At best, the families of the compounds present are suggested. This review also shows that the volatile halogenated compounds, fatty acids and sterols that are biosynthesized by the Asparagopsis species are relatively well known. Many other non-volatile metabolites (halogen compounds, flavonoids, other phenolic compounds) seem to be produced by these species, but their chemical structures and properties haven'been investigated. This shows how much remains to be investigated regarding the secondary-metabolite composition of these species, suggesting further studies following more targeted methodologies. [ABSTRACT FROM AUTHOR]

Halogenated compounds are one of the largest groups of environmental-hazardous chemicals. The removal of the halogen atom from the substrate is possible by the catalytic activity of a type of enzyme called dehalogenase. Hydrolytic dehalogenases are suggested to be a good biodegradation catalyst for halogenated compounds with potential bioremediation applications. Therefore, the identification of possible bacterial strains that produce dehalogenase is of great importance. Soil microorganisms that are regularly exposed to halogenated pesticides are a major source of hydrolytic dehalogenase. Their proper identification may be useful in the production of high-quality dehalogenase. DNA stable isotope probing (DNA-SIP) is quite a useful technique for the identification of active microorganisms that assimilate specific carbon substrates and nutrients. Metagenomics combined with a stable isotope probe (SIP) technique could therefore be used to detect bacterial dehalogenases in pesticides exposed agricultural soil. [ABSTRACT FROM AUTHOR]

Halogenated compounds pose long-term potential risks to the well-being of humans due to their recalcitrance and persistent toxicity. The quest for microorganisms capable of degrading such perilous substances merits urgent consideration. In this study, a new dehalogenase-producing bacterium was isolated from a hypersaline environment (TuzGölü Lake, Turkey), and identified as Bacillus megaterium strain CTBmeg1 (Accession number MK128900). Under culture conditions (pH 8.0, NaCl 20%, 30 °C, 200 rpm, 9 days), the B. megaterium strain CTBmeg1 showed an optimum growth on 10 mmol/L of 2,2-dichloropropionic acid with a doubling time of 26.41 h. Furthermore, the presence of a putative halotolerant dehalogenase gene (dehCTBmeg1) of B. megaterium strain CTBmeg1 was detected and amplified via PCR technique. Bio-prospecting for microorganisms in a highly saline environment capable of utilizing halogenated compounds as the sole carbon may prove to be a practical and safer means for bioremediation of contaminated coastal areas, an increasingly common place predicament faced by many nations.

A novel solvent-loaded dispersive solid-phase extraction (SL-DSPE) method integrated with liquid-phase microextraction (LPME) has been developed by the direct loading of solvent into the pores of a metal-organic framework (MOF), MIL-101(Cr)-NH2. Despite numerous advantages of MOFs, they are usually highly hydrophobic which limits their dispersibility and therefore effective contact with the analytes in aqueous samples. To overcome this and promote its interactions with polar compounds, MIL-101(Cr) was functionalized with –NH2 and loaded with a comparatively polar organic solvent, dichloromethane. The purpose of dichloromethane was to condition the MIL-101(Cr)-NH2, promote LPME of the analytes and facilitate the re-collection of the materials after the extraction. Five chlorophenoxy acid herbicides, including 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, and 2-(2,4,5-trichlorophenoxy)propionic acid, were studied and determined by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). MIL-101(Cr)-NH2 was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and surface area measurement. Several extraction parameters were optimized, and under the most favorable conditions, the SL-DSPE-UHPLC-MS/MS method achieved enrichment factors between 25 and 66. Low limits of detection (2.66–19.7 ng·L−1) and wide dynamic working ranges with good linearity (r2 ≥ 0.991) were attained for all analytes. The method was repeatable, with intra- and inter-day relative standard deviations (RSDs) below 4.5 and 7.6%, respectively, for three replicate determinations. The application of SL-DSPE-UHPLC-MS/MS to paddy field waters gave satisfactory relative recoveries ranging between 80.2 and 108%, with RSDs better 8.4%. Several of the CPAs were detected in these samples. [ABSTRACT FROM AUTHOR]

Dehalogenases are microbial enzyme catalysed the cleavage of carbon-halogen bond of halogenated organic compounds. It has potential use in the area of biotechnology such as bioremediation and chemical industry. Halogenated organic compounds can be found in a considerable amount in the environment due to utilization in agriculture and industry, such as pesticides and herbicides. The presence of halogenated compound in the environment have been implicated on the health and natural ecosystem. Microbial dehalogenation is a significant method to tackle this problem. This review intends to briefly describe the microbial dehalogenases in relation to the environment where they are isolated. The basic information about dehalogenases in relation to dehalogenation mechanisms, classification, sources and the transportation of these pollutants into bacterial cytoplasm will be described. We also summarised readily available synthetic halogenated organic compound in the environment. [ABSTRACT FROM AUTHOR]

The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, unlike terrestrial plants, produce a range of halogenated secondary metabolites, especially chlorinated and brominated compounds. Some orders of brown seaweeds also accumulate iodine, up to 1.2% of their dry weight. Fluorine remains rather unusual within the chemical structure. Halogenated hydrocarbons have moderate to high toxicities. In addition, halogenated organic compounds constitute a large group of environmental chemicals due to their extensive use in industry and agriculture. In recent years, concerns over the environmental fate and release of these halogenated organic compounds have resulted in research into their biodegradation and the evidence emerging shows that many of these compounds are more easily degraded under strictly anaerobic conditions compared to aerobic biodegradation. Biosorption via seaweed has become an alternative to the existing technologies in removing these pollutants. Halogenated compounds are known inhibitors of methane production from ruminants and humanmade anaerobic digesters. The focus of this paper is reviewing the available information on the effects of halogenated organic compounds on anaerobic digestion. [ABSTRACT FROM AUTHOR]

Resistance to the existing drugs and increasing numbers of diseases result in identifying new drug candidates with new forms of activity. As marine organisms are well known to provide a wide range of original compounds, Herein, we report the synthesis of new non-natural brominated, iodinated and chlorinated-substituted 1-O-alkylglycerols 5–7, analogs of a prominent 1-O-alkylglycerol (AKG) of the natural shark liver oil (SLO) mixture, namely the AKGs 18:1, n-9. [ABSTRACT FROM AUTHOR]

[Display omitted] • A general, selective, and sensitive probe for volatile halogenated carbonyl compounds. • The detection limit of the fluorescent probe was at the nM level. • Application of the probe in the efficient determination of yields for organic reactions. • Mechanism studies revealed a non-bonding interaction of analyst and probe. The fluorescent detection of neutral and volatile carbonyl halogenated compounds had not been studied before. We describe here a simple and sensitive turn-on rhodamin fluorescent probe for the selective detection of fluorinated/brominated/chlorinated/iodinated carbonyl compounds. A wide range of linear or cyclic volatile organic halides was detected with a limit of detection as low as 45.6 nM within 1 min. Mechanistic experiments and DFT calculations indicate the reversible formation of a 1:1 complex of sensor and analyst through non-bonding interaction. [ABSTRACT FROM AUTHOR]

ABSTRACT Marine sponges are recognized as valuable sources of bioactive metabolites and renowned as petri dishes of the sea, providing specialized niches for many symbiotic microorganisms. Sponges of the family Dysideidae are well documented to be chemically talented, often containing high levels of polyhalogenated compounds, terpenoids, peptides, and other classes of bioactive small molecules. This group of tropical sponges hosts a high abundance of an uncultured filamentous cyanobacterium, Hormoscilla spongeliae. Here, we report the comparative genomic analyses of two phylogenetically distinct Hormoscilla populations, which reveal shared deficiencies in essential pathways, hinting at possible reasons for their uncultivable status, as well as differing biosynthetic machinery for the production of specialized metabolites. One symbiont population contains clustered genes for expanded polybrominated diphenylether (PBDE) biosynthesis, while the other instead harbors a unique gene cluster for the biosynthesis of the dysinosin nonribosomal peptides. The hybrid sequencing and assembly approach utilized here allows, for the first time, a comprehensive look into the genomes of these elusive sponge symbionts. IMPORTANCE Natural products provide the inspiration for most clinical drugs. With the rise in antibiotic resistance, it is imperative to discover new sources of chemical diversity. Bacteria living in symbiosis with marine invertebrates have emerged as an untapped source of natural chemistry. While symbiotic bacteria are often recalcitrant to growth in the lab, advances in metagenomic sequencing and assembly now make it possible to access their genetic blueprint. A cell enrichment procedure, combined with a hybrid sequencing and assembly approach, enabled detailed genomic analysis of uncultivated cyanobacterial symbiont populations in two chemically rich tropical marine sponges. These population genomes reveal a wealth of secondary metabolism potential as well as possible reasons for historical difficulties in their cultivation.

• Key volatile pollutants in the gaseous emissions of MSW were assessed. • Ethanol, methyl mercaptan and H 2 S were key pollutants during airtight storage stage. • DMDS, 1,2-dichloroethane and trichloroethylene were key pollutants during ventilation. Gaseous emissions from municipal solid waste (MSW) have raised many concerns and complaints. Identifying the key volatile pollutants in the complex gaseous emissions from MSW is significant for the efficient mitigation of their odor nuisances and health risks. For this purpose, we present an integrated investigation of the key volatile pollutants in the gaseous emissions of MSW from the perspectives of emission patterns, odor concentrations and health risks. Air samples were collected during four different emission stages of the waste matrix for both chemical and olfactometric analyses. The total chemical concentrations of the volatile compounds in the air samples were in the range of 21.49 mg m−3 to 295.61 mg m−3, and the odor concentrations varied from 1122 ou E m−3 to 17,782 ou E m−3. The odor concentrations in the air samples were well correlated with the odor activity values (OAV s) of sulfur compounds, oxygenated compounds and ammonia (r = 0.922, 0.879 and 0.780, respectively, for n = 17 and p < 0.01). Moreover, from an integrated perspective involving chemical emissions, the proportions of odor concentrations and health risks, ethanol, methyl mercaptan and hydrogen sulfide were identified as the key volatile pollutants in the gaseous emissions from the waste matrix during the airtight storage stage, and dimethyl disulfide, 1,2-dichloroethane and trichloroethylene were the key volatile pollutants during the ventilation stage. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) was explored as a sorbent for the emulsification-enhanced (EE) disposable pipette extraction (DPX) of eight organochlorine pesticides (OCPs) from environmental waters. The OCPs, including α-hexachlorocyclohexane, Aldrin, α-Chlordane, Dieldrin, 4,4′-dichlorodiphenyldichloroethylene, 4,4′-dichlorodiphenyldichloroethane, Heptachlor and Heptachlor epoxide (Isomer A), were analyzed by gas chromatography-mass spectrometry. The sorbent g-C3N4 was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, g-C3N4 exhibits good water dispersibility and allows easy analyte recovery – a characteristic not commonly observed in carbon-based materials. When applied to DPX, g-C3N4 rapidly establishes strong interactions with the OCPs. Consequently, g-C3N4 displays superior extraction capability in comparison to six other commercial sorbents. An emulsification step prior to DPX was found to enhance the overall extraction efficiency by pre-concentrating the OCPs into the microdroplets of an organic solvent. The microdroplets were then adsorbed onto g-C3N4. Under the most favorable conditions, wide linear responses spanning over two to four orders of magnitudes are established. The limits of detection range between 2.4 ng·L−1 and 46.2 ng·L−1. The method is reproducible (relative standard deviations ≤ 7.4%) and enrichment factors are between 42 and 57. When applied to the analysis of lake and river water samples, EE-DPX-gas chromatography-mass spectrometry exhibits good resilience against matrix interferences. The relative recoveries range between 77.7% and 106.3%. In comparison to other sorbent-based extraction techniques reported for the analysis of OCPs in aqueous samples, EE-DPX utilizes the minimal amount of sample and solvent, and requires the shortest sample preparation time. [ABSTRACT FROM AUTHOR]

Halogenated compounds pose long-term potential risks to the well-being of humans due to their recalcitrance and persistent toxicity. The quest for microorganisms capable of degrading such perilous substances merits urgent consideration. In this study, a new dehalogenase-producing bacterium was isolated from a hypersaline environment (TuzGölü Lake, Turkey), and identified as Bacillus megaterium strain CTBmeg1 (Accession number MK128900). Under culture conditions (pH 8.0, NaCl 20%, 30 °C, 200 rpm, 9 days), the B. megaterium strain CTBmeg1 showed an optimum growth on 10 mmol/L of 2,2-dichloropropionic acid with a doubling time of 26.41 h. Furthermore, the presence of a putative halotolerant dehalogenase gene (dehCTBmeg1) of B. megaterium strain CTBmeg1 was detected and amplified via PCR technique. Bio-prospecting for microorganisms in a highly saline environment capable of utilizing halogenated compounds as the sole carbon may prove to be a practical and safer means for bioremediation of contaminated coastal areas, an increasingly common place predicament faced by many nations. [ABSTRACT FROM AUTHOR]

Halogenated compounds are well‐known for their diverse bioactivities and wide applications in pharmaceutical industry, chemical engineering and other fields. Novel halometabolites isolated from nature inspire scientists to synthesize these "chance compounds", which were, however, usually hampered by the extreme catalytic conditions and severe selectivity challenges. In the past several decades, enzymatic reactions have been brought into attention for their efficiency, selectivity, and mild reaction conditions. Synthetic biology which is in compliance with the laws of nature to a large extent shed light on the rational biosynthesis of halogenated compounds. This article summarizes several representative categories of halogenated natural products and halogenases to seek clues to the relationship between the structures and halogenase mechanisms. Some types of halogenase convert the basic building blocks to diverse early intermediates during natural product biosynthetic processes, while others are involved in the late tailoring steps to afford the final structures of halogenated molecules. The broad substrate specificity and strong regioselectivity exhibited in some halogenases are irreplaceable advantages for biosynthesis. In addition, tremendous efforts and encouraging results enable us to engineer the enzymes or techniques to synthesize "unnatural" halogenated natural products. More reaction mechanisms and structural data are expected to be revealed exponentially in this rapid growing realm. [ABSTRACT FROM AUTHOR]

Marine actinomycetes, Streptomyces species, produce a variety of halogenated compounds with diverse structures and a range of biological activities owing to their unique metabolic pathways. These halogenated compounds could be classified as polyketides, alkaloids (nitrogen-containing compounds) and terpenoids. Halogenated compounds from marine actinomycetes possess important biological properties such as antibacterial and anticancer activities. This review reports the sources, chemical structures and biological activities of 127 new halogenated compounds originated mainly from Streptomyces reported from 1992 to 2020.

In the combination of 5-fluorophenyl-1, 3, 7, 9-tetra methyl pyrido [2, 3, d, d, 5, 6 di pyrimidine -2, 4, 6, and 8 tetron, there are 4 rings, respectively, ring that is attached to the halogen ring A and, respectively, a ring The lower and the right to the left of the ring A are called C, B, and D. Calculations and studies show that the amount of aromatics in halogen-ring A in all cases has the highest amount. In the B and D loop, the predicted aromaticity level is low and close to zero, and there is a reduction in aromatics in the C loop than the A ring. In another stage of the study, with the replacement of the halogen ring A from F to I, the following trend was observed. In ring A, when halogens were changed, the increase in aromaticity in halogenated compounds was as follows: F> Cl> Br> I.

The seaweed Asparagopsis armata exhibits a strong invasive behavior, producing halogenated compounds with effective biological effects. This study addresses the biochemical responses to sublethal concentrations of A. armata exudate on the marine snail Gibbula umbilicalis whole body and the shrimp Palaemon elegans eyes and hepatopancreas. Antioxidant defenses superoxide dismutase (SOD) and glutathione-S-transferase (GST), oxidative damage endpoints lipid peroxidation (LPO) and DNA damage, the neuronal parameter acetylcholinesterase (AChE), and the fatty acid profile were evaluated. Results revealed different metabolic responses in both species. Despite previous studies indicating that the exudate affected G. umbilicalis’ survival and behavior, this does not seem to result from oxidative stress or neurotoxicity. For P. elegans, the inhibition of AChE and the decrease of antioxidant capacity is concomitant with the increase of LPO, suggesting neurotoxicity and oxidative stress as contributor mechanisms of toxicity for this species. Fatty acid profile changes were more pronounced for P. elegans with a general increase in polyunsaturated fatty acids (PUFAs) with the exudate exposure, which commonly means a defense mechanism protecting from membrane disruption. Nonetheless, the omega-3 PUFAs arachidonic acid (ARA) and docosapentaenoic acid (DPA) increased in both invertebrates, indicating a common regulation mechanism of inflammation and immunity responses.

Marine fungi produce many halogenated metabolites with a variety of structures, from acyclic entities with a simple linear chain to multifaceted polycyclic molecules. Over the past few decades, their pharmaceutical and medical application have been explored and still the door is kept open due to the need of new drugs from relatively underexplored sources. Biological properties of halogenated compounds such as anticancer, antiviral, antibacterial, anti-inflammatory, antifungal, antifouling, and insecticidal activity have been investigated. This review describes the chemical structures and biological activities of 217 halogenated compounds derived mainly from Penicillium and Aspergillus marine fungal strains reported from 1994 to 2019.

The urgent need to replace fossil fuels has seen macroalgae advancing as a potential feedstock for anaerobic digestion. The natural methane productivity (dry weight per hectare) of seaweeds is greater than in many terrestrial plant systems. As part of their defence systems, seaweeds, unlike terrestrial plants, produce a range of halogenated secondary metabolites, especially chlorinated and brominated compounds. Some orders of brown seaweeds also accumulate iodine, up to 1.2% of their dry weight. Fluorine remains rather unusual within the chemical structure. Halogenated hydrocarbons have moderate to high toxicities. In addition, halogenated organic compounds constitute a large group of environmental chemicals due to their extensive use in industry and agriculture. In recent years, concerns over the environmental fate and release of these halogenated organic compounds have resulted in research into their biodegradation and the evidence emerging shows that many of these compounds are more easily degraded under strictly anaerobic conditions compared to aerobic biodegradation. Biosorption via seaweed has become an alternative to the existing technologies in removing these pollutants. Halogenated compounds are known inhibitors of methane production from ruminants and humanmade anaerobic digesters. The focus of this paper is reviewing the available information on the effects of halogenated organic compounds on anaerobic digestion.

Humans and their associated microbiomes are exposed to numerous xenobiotics through drugs, dietary components, personal care products as well as environmental chemicals. Most of the reciprocal interactions between the microbiota and xenobiotics, such as halogenated compounds, occur within the human gut harboring diverse and dense microbial communities. Here, we provide an overview of the flux of halogenated compounds in the environment, and diverse exposure routes of human microbiota to these compounds. Subsequently, we review the impact of halogenated compounds in perturbing the structure and function of gut microbiota and host cells. In turn, cultivation-dependent and metagenomic surveys of dehalogenating genes revealed the potential of the gut microbiota to chemically alter halogenated xenobiotics and impact their fate. Finally, we provide an outlook for future research to draw attention and attract interest to study the bidirectional impact of halogenated and other xenobiotic compounds and the gut microbiota.

Humans and their associated microbiomes are exposed to numerous xenobiotics through drugs, dietary components, personal care products as well as environmental chemicals. Most of the reciprocal interactions between the microbiota and xenobiotics, such as halogenated compounds, occur within the human gut harboring diverse and dense microbial communities. Here, we provide an overview of the flux of halogenated compounds in the environment, and diverse exposure routes of human microbiota to these compounds. Subsequently, we review the impact of halogenated compounds in perturbing the structure and function of gut microbiota and host cells. In turn, cultivation-dependent and metagenomic surveys of dehalogenating genes revealed the potential of the gut microbiota to chemically alter halogenated xenobiotics and impact their fate. Finally, we provide an outlook for future research to draw attention and attract interest to study the bidirectional impact of halogenated and other xenobiotic compounds and the gut microbiota. [ABSTRACT FROM AUTHOR]

Asparagopsis taxiformis concentrates halogenated compounds that are known to inhibit cobamide-dependent methanogenesis in vitro and, therefore, has potential to mitigate enteric methane production. The present study investigated the effect of Asparagopsis on methane (CH4) production from sheep offered a high-fibre pelleted diet (offered at 1.2 x maintenance) at five inclusion levels of Asparagopsis for 72 days (0% (control), 0.5%, 1%, 2% and 3% organic matter basis as offered). Individual animal CH4 measurements were conducted at 21-day intervals using open-circuit respiration chambers. Asparagopsis inclusion resulted in a consistent and dose-dependent reduction in enteric CH4 production over time, with up to 80% CH4 mitigation at the 3% offered rate compared with the group fed no Asparagopsis (P < 0.05). Sheep fed Asparagopsis had a significantly lower concentration of total volatile fatty acids and acetate, but a higher propionate concentration. Nochanges in liveweight gain were identified. Supplementing Asparagopsis in a high-fibre diet (<2%organic matter) resulted in significant and persistent decreases in enteric methanogenesis over a 72-day period. Granulomatous and keratotic ruminal mucosa changes were identified in several sheep with Asparagopsis supplementation. While the outcomes of the present study may be extrapolated to feedlot to achieve the antimethanogenic effect associated with Asparagopsis, further work is required to define the long-term effects on productivity and animal health. [ABSTRACT FROM AUTHOR]

The title molecule, C6H6Br2N2, is almost planar (r.m.s. deviation for the non-H atoms = 0.012 Å). In the crystal, inversion dimers linked by pairs of N—H...N hydrogen bonds generate R22(8) loops.

Treating water contaminants via heterogeneously catalyzed reduction reaction is a subject of growing interest due to its good activity and superior selectivity compared to conventional technology, yielding products that are non-toxic or substantially less toxic. This article reviews the application of catalytic reduction as a progressive approach to treat different types of contaminants in water, which covers hydrodehalogenation for wastewater treatment and hydrogenation of nitrate/nitrite for groundwater remediation. For hydrodehalogenation, an overview of the existing treatment technologies is provided with an assessment of the advantages of catalytic reduction over the conventional methodologies. Catalyst design for feasible catalytic reactions is considered with a critical analysis of the pertinent literature. For hydrogenation, hydrogenation of nitrate/nitrite contaminants in water is mainly focused. Several important nitrate reduction catalysts are discussed relating to their preparation method and catalytic performance. In addition, novel approach of catalytic reduction using in situ synthesized H evolved from water splitting reaction is illustrated. Finally, the challenges and perspective for the extensive application of catalytic reduction technology in water treatment are discussed. This review provides key information to our community to apply catalytic reduction approach for water treatment. [ABSTRACT FROM AUTHOR]

In carbon and silicon tetrahalide compounds, the experimental 13C and 29Si NMR chemical-shift values are known to increase or decrease on increasing the overall sum of the ionic radii of the bonded halides Σ( rh) (normal and inverse halogen dependence (NHD and IHD, respectively)). Herein, we extrapolate the main factors responsible for such NMR chemical shifts. Intriguingly, we found a characteristic value for the overall sum of the Pauling electronegativities of the bonded halides Σ( χh), which works as a triggering factor to determine the transition from the NHD to IHD. Below this Σ( χh) value, the chemical shift of the central atom was strictly related to only the Σ( rh) value, thus producing a NHD trend. Conversely, above this value, the chemical shift of the central atom was dependent on both the Σ( rh) and Σ( χh) values, thus producing a IHD trend. A simple model, in which the effect of the Σ( χh) value on 13C and 29Si NMR chemical shifts is related to an apparent increase in the Σ( rh) value, is deduced. [ABSTRACT FROM AUTHOR]

This study put a great emphasis on the role of carbon dioxide (CO 2 ) in thermal decomposition of polyvinyl chloride (PVC). To do this, systematic experimental works were carried out to explore the influence of CO 2 on pyrolysis of PVC by comparing with that in N 2 . First of all, a series of thermo-gravimetric analysis (TGA) of PVC in N 2 and CO 2 was performed to characterize the thermal deconstruction of PVC in N 2 and CO 2 , which confirmed that any physical aspect ( i.e. , onset and end temperature of depolymerization of PVC) attributed by CO 2 was nearly negligible as compared to the case in N 2 . This phenomenon was also fully evidenced by differential thermogram (DTG) and differential scanning calorimeter (DSC) because both DTG and DSC curves in N 2 and CO 2 were identical. However, the concentration profiles of CO evolved from the thermal degradation of PVC in N 2 and CO 2 was significantly different: the enhanced generation of CO occurred in the presence of CO 2 . This observation suggested that the genuine role of CO 2 is to consume carbon source ( i.e. , acting as a carbon scavenger) for pyrolysis of PVC. It also provided a favorable condition for suppressing the formation of harmful chemical compounds such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). Therefore, the mass portion of the oil in pyrolytic products produced from pyrolysis of PVC in CO 2 was lower than that in N 2 . These particular thermal degradation behaviors may be explained by the genuine role of CO 2 : the enhanced thermal cracking of volatile organic carbons (VOCs) evolved from the pyrolysis of PVC. The findings of this study strongly suggest that CO 2 can be effectively applied to thermal disposal of recalcitrant wastes since employing CO 2 in thermal treatment provides a means for in-situ mitigation and/or reduction of harmful chemical species. [ABSTRACT FROM AUTHOR]

Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds.

The palladium-catalysed aqueous α-arylation of ketones was developed and tested for a large variety of reaction partners. These mild conditions enabled the coupling of aryl/alkyl-ketones with N-protected halotryptophans, heterocyclic haloarenes, and challenging base-sensitive compounds. The synthetic potential of this new methodology for the diversification of complex bioactive molecules was exemplified by derivatising prochlorperazine. The methodology is mild, aqueous and flexible, representing a means of functionalizing a wide range of halo-aromatics and therefore has the potential to be extended to complex molecule diversification. [ABSTRACT FROM AUTHOR]

Simultaneous immobilization of heavy metals and decomposition of halogenated organic compounds in different fractions of automobile shredder residue (ASR) were achieved with a nano-sized metallic calcium through a 60-min ball milling treatment. Heavy metal (HM) immobilization and chlorinated/brominated compound (CBC) decomposition efficiencies both reached 90-100 %, after ball milling with nanometallic calcium/calcium oxide (Ca/CaO) dispersion, regardless of ASR particle size (1.0, 0.45-1.0, and 0.250 mm). Concentrations of leachable HMs substantially decreased to a level lower than the regulatory standard limits (Co and Cd 0.3 mg L; Cr 1.5 mg L; Fe, Pb, and Zn 3.0 mg L; Mn and Ni 1 mg L) proposed by the Korean hazardous waste elution standard regulatory threshold. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) element maps/spectra showed that while the amounts of HMs and CBCs detectable in ASR significantly decreased, the calcium mass percentage increased. X-ray powder diffraction (XRD) patterns indicate that the main fraction of enclosed/bound materials on ASR includes Ca-associated crystalline complexes that remarkably inhibit HM desorption and simultaneously transform dangerous CBCs into harmless compounds. The use of a nanometallic Ca/CaO mixture in a mechanochemical process to treat hazardous ASR (dry conditions) is an innovative approach to remediate cross-contaminated residues with heavy metals and halogenated compounds. [ABSTRACT FROM AUTHOR]

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Halogenated chiral molecules have become important in several fields of science, industry, and society as drugs, natural compounds, agrochemicals, environmental pollutants, synthetic products, and chiral supports. Meanwhile, the perception of the halogen moiety in organic compounds and its role in recognition processes changed. Indeed, the recognition of the halogen bond as an interaction occurring when the halogen acts as a Lewis acid had a strong impact, particularly in and medicinal chemistry. Due to this renewed interest in the potentialities of chiral organohalogens, here we focus on selected recent applications dealing with enantioseparations of halogenated compounds on polysaccharide-based chiral stationary phases (CSPs), widely used in (LC). In particular, recently the first case of halogen bonding-driven high-performance LC (HPLC) enantioseparation was reported on a cellulose-based CSP. Along with enantioseparations performed under conventional HPLC, representative applications using (SFC) are reported. Chirality 27:667-684, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A purity specification in an international standard (ISO 14687) for hydrogen for use in proton exchange membrane fuel cells is discussed. The specification, which is referenced in a recent EU directive, sets maximum limits for 14 impurities in hydrogen. We consider one entry in the specification, total halogenated compounds, and conclude that no currently available analytical method is able to measure total halogenated compounds in a robust, traceable and accurately quantifiable manner. Three suggestions for addressing this problem when the standard is revised are given, namely (1) replacing 'total halogenated compounds' with a list of key halogenated compounds that can be measured individually, (2) identifying compounds whose measurement is more routine to act as 'canary species' for hydrogen produced from different sources and (3) setting different specifications for hydrogen produced from different sources. Prior to the revision of ISO 14687, we propose that inductively coupled plasma mass spectroscopy provides the best currently available analytical solution to estimate the amount fraction of halogenated compounds in hydrogen. [ABSTRACT FROM AUTHOR]

In recent years, we have intensively studied the ion chemistry of halogenated substances in ion mobility spectrometry (IMS). During atmospheric pressure chemical ionization (APCI) processes, dissociative electron transfer reactions between reactant ions and halogenated molecules occur and (HO)X product ions are formed, which appear as distinct product ion peak in negative ion mobility spectra. These product ion peaks (obtained for different compounds) were used for comparing differences in detectability, sensitivity, peak position and resolution. We identified that structural features clearly affect detection capability in IMS, which can be attributed to the different bonding states of halogens within the molecule. Then we subsequently established that the resulting different bond strengths also determine the degree of mutual influence when various halogenated substances are simultaneously investigated. Regarding the experimental conditions, we observed that increasing humidity generally leads to a decrease in the relative abundance of product ions. However, the effect of humidity strongly depends on the way in which the water vapor is transported into the ion mobility spectrometer (carrier or drift gas). In contrast to the results achieved which were affected by increased humidity, elevating IMS cell temperatures resulted in more accurate detection of all substances investigated. [ABSTRACT FROM AUTHOR]