The diversity of naturally produced organohalogens

Freeze-induced acceleration of iodide oxidation and consequent iodination of dissolved organic matter to form organoiodine compounds

Freeze-induced acceleration of I- oxidation and the consequent iodination of dissolved organic matter (DOM) contribute to the formation of organoiodine compounds (OICs) in cold regions. The formed OICs may be a potentially important source of risk and are very closely with the environment and human health. Herein, we investigated the acceleration effects of the freeze process on I- oxidation and the formation of OICs. In comparison to reactive iodine species (RIS) formed in aqueous solutions, I- oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH, and the content of I- and O2. Freeze-thaw process further promoted I- oxidation and the concentration of RIS reached 45.7 µmol/L after 6 freeze-thaw cycles. The consequent products of DOM iodination were greatly promoted in terms of both concentration and number. The total content of OICs ranged from 0.02 to 2.83 µmol/L under various conditions. About 183-1197 OICs were detected by Fourier transform ion cyclotron resonance mass spectrometry, and more than 96.2% contained one or two iodine atoms. Most OICs had aromatic structures and were formed via substitution and addition reactions. Our findings reveal an important formation pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.

Silver-Catalyzed Carbofluorination of Olefins and α-Fluoroolefins with Carbamoyl Radicals

The reactivity of carbamoyl radicals, generated in situ from sodium oxamate salts, has been investigated in the context of radical carbofluorination reactions of olefins and α-fluoroolefins, respectively. Both transformations are catalyzed by silver salts and required the presence of potassium persulfate (K2S2O8) and SelectfluorTM as a radicophilic fluorine source. The reported methods provide a direct access to β-fluoroamides and β,β-difluoroamides.

Expanding Chemical Frontiers: Approaches for Generating Diverse and Bioactive Natural Product-Like Compounds Libraries from Extracts

The realms of natural products and synthetic compounds exhibit distinct chemical spaces that not only differ but also complement each other. While the convergence of these two domains has been explored through semisynthesis and conventional pharmacomodulation endeavours applied to natural frameworks, a recent and innovative approach has emerged that involves the combinatorial generation of libraries of 'natural product-like compounds' (NPLCs) through the direct synthetic derivatization of natural extracts. This has led to the production of numerous NPLCs that incorporate structural elements from both their natural (multiple saturated rings, oxygen content, chiral centres) and synthetic (aromatic rings, nitrogen and halogen content, drug-like properties) precursors. Through careful selection of extracts and reagents, specific bioactivities have been achieved, and this strategy has been deployed in various ways, showing great promise without reaching its full potential to date. This review seeks to provide an overview of reported examples involving the chemical engineering of extracts, showcasing a spectrum of natural product alterations spanning from simple substitutions to complete scaffold remodelling. It also includes an analysis of the accomplishments, perspectives and technical challenges within this field.

Spatial distribution characteristics of carbazole and polyhalogenated carbazoles in water column and sediments in the open Western Pacific Ocean

Polyhalogenated carbazoles (PHCZs), an emerging persistent halogenated organic pollutant, have been detected in the environment. However, our understanding of PHCZs in the ocean remains limited. In this study, 47 seawater samples (covering 50 - 4000 m) and sediment samples (49 surface and 3 cores) were collected to investigate the occurrence and spatial distribution patterns of carbazole and its halogenated derivants (CZDs) in the Western Pacific Ocean. In seawater, the detection frequencies of CZ (97.87%) and 3-CCZ (57.45%) were relatively high. In addition, the average concentration of ΣPHCZs in the upper water (< 150 m, 0.23 ± 0.21 ng/L) was significantly lower than that in the deep ocean (1000 - 4000 m, 0.65 ± 0.56 ng/L, P < 0.05), which may indicate the vertical transport of PHCZs in the marine environment. The concentration of ΣCZDs in surface sediment ranges from 0.46 to 6.48 ng/g (mean 1.54 ng/g), among which CZ and 36-CCZ were the predominant components. Results from sediment cores demonstrate a noteworthy negative correlation between the concentration of CZDs and depth, indicating the ongoing natural degradation process occurring in sediment cores over a long period. This study offers distinctive insights into the occurrence, composition, and vertical features of CZDs in oceanic environments.

D3Rings: A Fast and Accurate Method for Ring System Identification and Deep Generation of Drug-Like Cyclic Compounds

Continuous exploration of the chemical space of molecules to find ligands with high affinity and specificity for specific targets is an important topic in drug discovery. A focus on cyclic compounds, particularly natural compounds with diverse scaffolds, provides important insights into novel molecular structures for drug design. However, the complexity of their ring structures has hindered the applicability of widely accepted methods and software for the systematic identification and classification of cyclic compounds. Herein, we successfully developed a new method, D3Rings, to identify acyclic, monocyclic, spiro ring, fused and bridged ring, and cage ring compounds, as well as macrocyclic compounds. By using D3Rings, we completed the statistics of cyclic compounds in three different databases, e.g., ChEMBL, DrugBank, and COCONUT. The results demonstrated the richness of ring structures in natural products, especially spiro, macrocycles, and fused and bridged rings. Based on this, three deep generative models, namely, VAE, AAE, and CharRNN, were trained and used to construct two data sets similar to DrugBank and COCONUT but 10 times larger than them. The enlarged data sets were then used to explore the molecular chemical space, focusing on complex ring structures, for novel drug discovery and development. Docking experiments with the newly generated COCONUT-like data set against three SARS-CoV-2 target proteins revealed that an expanded compound database improves molecular docking results. Cyclic structures exhibited the best docking scores among the top-ranked docking molecules. These results suggest the importance of exploring the chemical space of structurally novel cyclic compounds and continuous expansion of the library of drug-like compounds to facilitate the discovery of potent ligands with high binding affinity to specific targets. D3Rings is now freely available at http://www.d3pharma.com/D3Rings/.

Composition and sources of sediment organic matter in a western Iberian salt marsh: Developing a novel prediction model of the bromine sedimentary pool

Salt marshes are sensitive highly productive habitats crucial for carbon cycling. This study presents a comprehensive analysis of organic geochemical indicators and geochronology in the Mira salt marsh (SW Portugal) over eight centuries. The closely intertwined carbon and bromine (Br) biogeochemical cycles in these environments can influence the fluxes of volatile compounds such as ozone-depleting methyl bromide, emphasizing the importance of understanding sediment organic matter (OM) origin, budget, and composition in salt marshes. To characterize the strong Br-OM relationship, we used n-alkane signatures, bulk elemental data (total carbon, total nitrogen, Corg/Nat ratio), and stable isotopes (δ15N, δ13C) from a sediment core. Findings revealed a mixed composition of terrestrial and marine OM, posing challenges in distinguishing ex situ higher plant sources from in situ production by marsh vegetation. n-Alkanes (C15 to C31) were found in all the sediment samples, predominantly C25-C29. Changes in their presence were linked to marsh succession, evolving from a vegetation-free tidal flat to a C3 halophyte-dominated high marsh ecosystem. Despite the area's low industrial and population impact, regulation of water flow through the dam affected the balance between continental and marine waters. This study aimed to create a cost-effective predictive model for total Br, enhancing paleoclimatic studies using sedimentary samples. The n-alkane model had limited resolution, but an alternative infrared (IR) spectroscopy-based model, requiring less time and smaller sample sizes, was developed. Combining FT-IR spectra with statistical analysis enabled the creation of a reliable total Br concentration prediction model (mean absolute error = 14.39). These findings have implications for controlling Br enrichment in marsh environments and can be applied in various coastal wetlands with different mineralogical and organic characteristics.

Marine-derived Compounds: A Powerful Platform for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a debilitating form of dementia that primarily affects cholinergic neurons in the brain, significantly reducing an individual's capacity for learning and creative skills and ultimately resulting in an inability to carry out even basic daily tasks. As the elderly population is exponentially increasing, the disease has become a significant concern for society. Therefore, neuroprotective substances have garnered considerable interest in addressing this universal issue. Studies have shown that oxidative damage to neurons contributes to the pathophysiological processes underlying AD progression. In AD, tau phosphorylation and glutamate excitotoxicity may play essential roles, but no permanent cure for AD is available. The existing therapies only manage the early symptoms of AD and often come with numerous side effects and toxicities. To address these challenges, researchers have turned to nature and explored various sources such as plants, animals, and marine organisms. Many historic holy books from different cultures emphasize that adding marine compounds to the regular diet enhances brain function and mitigates its decline. Consequently, researchers have devoted significant time to identifying potentially active neuroprotective substances from marine sources. Marine-derived compounds are gaining recognition due to their abundant supply of diverse chemical compounds with biological and pharmacological potential and unique mechanisms of action. Several studies have reported that plants exhibit multitarget potential in treating AD. In light of this, the current study focuses on marine-derived components with excellent potential for treating this neurodegenerative disease.

Driving factors influencing spatiotemporal variation of natural organic chlorine in Shennongjia forest soil

Studying the geochemical behavior of chlorine is the basis of understanding the chlorine cycle in nature. To explore the spatiotemporal distribution of natural organic chlorine (Clorg), L layer (litter fall), F-H layer (humification zone), topsoil layer (0-20 cm), and deep soil layer (20-40 cm) samples were collected from 18 sampling sites at different altitudes (851-2918 m) in Shennongjia Forest in May, August, and December. Clorg content was analyzed, and the Clorg stocks were calculated. The major factors affecting the distribution of Clorg were explored. The results revealed that the sum of Clorg content in four layers varied from 7.958 to 184.686 mg/kg, and the highest value was observed in August. Clorg accounted for 46%-77% of total chlorine, with the highest mean ratio in soil layer (0-20 cm). Clorg content exhibited the following trend: F-H layer > L layer > topsoil layer (0-20 cm) > deep soil layer (20-40 cm). The seasonal patterns of Clorg in soil layers were different from that in L and F-H layers, which were mainly controlled by the content and humification degree of organic matter. Clorg storage was much higher in soil layers (61-246 kg/ha) than those in F-H layer (1.1-7.1 kg/ha) and in L layer (0.1-0.8 kg/ha) because of the large thickness of the soil layers. Overall, the Clorg content exhibited an increasing trend with altitude, except at an altitude of approximately 1800 m. Clorg content in L and F-H layers varied more obviously with altitude than that in soil layers. When inorganic chlorine (Clin) was not a limiting factor for the chlorination process, Clorg content in L and F-H layers was significantly affected by climate and organic matter controlled by altitude, while Clorg content in soil layers was also mediated by metal ions and pH, and soil particle size. This study could provide a scientific basis for assessing the chlorine cycle in nature.

Cl atoms-initiated degradation of 1-Chlorobutane and 2-Chlorobutane: Kinetics, product analysis and atmospheric implications

The relative rate method was employed to investigate the kinetics of the Cl-initiated reactions of 1-chlorobutane (1-CB) and 2-chlorobutane (2-CB) over 263-363 K, and the measured rate coefficients at room temperature are (1.04 ± 0.24) × 10-10 and (5.84 ± 0.27) × 10-11 cm3 molecule-1 s-1, respectively. The Arrhenius equations for the title reactions were derived to be k1-CB + Cl (T = 263-363 K) = (2.77 ± 0.72) × 10-11 exp [(422 ± 79)/T] and k2-CB + Cl (T = 263-363 K) = (1.40 ± 0.32) × 10-11 exp [(415 ± 70)/T] cm3 molecule-1 s-1, respectively. The products were analysed qualitatively using gas chromatography-mass spectrometry (GC-MS), and the reaction mechanism was proposed for the reactions. The rate coefficients for the title reactions were calculated computationally over the temperature range of 200-400 K using canonical variational transition state theory with appropriate tunnelling corrections at CCSD(T)/6-311++G(2d,2p)//BHandHLYP/6-311++G(2d,2p) level of theory to complement our experimentally measured kinetic parameters. The experimental and theoretical data obtained were used to evaluate the impact of the studied molecules in the troposphere.

Self-Similar Patterns from Abiotic Decarboxylation Metabolism through Chemically Oscillating Reactions: A Prebiotic Model for the Origin of Life

The origin of life must have included an abiotic stage of carbon redox reactions that involved electron transport chains and the production of lifelike patterns. Chemically oscillating reactions (COR) are abiotic, spontaneous, out-of-equilibrium, and redox reactions that involve the decarboxylation of carboxylic acids with strong oxidants and strong acids to produce CO₂ and characteristic self-similar patterns. Those patterns have circular concentricity, radial geometries, characteristic circular twins, colour gradients, cavity structures, and branching to parallel alignment. We propose that COR played a role during the prebiotic cycling of carboxylic acids, furthering the new model for geology where COR can also explain the patterns of diagenetic spheroids in sediments. The patterns of COR in Petri dishes are first considered and compared to those observed in some eukaryotic lifeforms. The molecular structures and functions of reactants in COR are then compared to key biological metabolic processes. We conclude that the newly recognised similarities in compositions and patterns warrant future research to better investigate the role of halogens in biochemistry; COR in life-forms, including in humans; and the COR-stage of prebiotic carbon cycling on other planets, such as Mars.

In silico analysis of a putative dehalogenase from the genome of halophilic bacterium Halomonas smyrnensis AAD6T

Microbial-assisted removal of natural or synthetic pollutants is the prevailing green, low-cost technology to treat polluted environments. However, the challenge with enzyme-assisted bioremediation is the laborious nature of dehalogenase-producing microorganisms' bioprospecting. This bottleneck could be circumvented by in-silico analysis of certain microorganisms' whole-genome sequences to predict their protein functions and enzyme versatility for improved biotechnological applications. Herein, this study performed structural analysis on a dehalogenase (DehHsAAD6) from the genome of Halomonas smyrnensis AAD6 by molecular docking and molecular dynamic (MD) simulations. Other bioinformatics tools were also employed to identify substrate preference (haloacids and haloacetates) of the DehHsAAD6. The DehHsAAD6 preferentially degraded haloacids and haloacetates (-3.2-4.8 kcal/mol) and which formed three hydrogen bonds with Tyr12, Lys46, and Asp182. MD simulations data revealed the higher stability of DehHsAAD6-haloacid- (RMSD 0.22-0.3 nm) and DehHsAAD6-haloacetates (RMSF 0.05-0.14 nm) complexes, with the DehHsAAD6-L-2CP complex being the most stable. The detail of molecular docking calculations ranked complexes with the lowest binding free energies as: DehHsAAD6-L-2CP complex (-4.8 kcal/mol) = DehHsAAD6-MCA (-4.8 kcal/mol) < DehHsAAD6-TCA (-4.5 kcal/mol) < DehHsAAD6-2,3-DCP (-4.1 kcal/mol) < DehHsAAD6-D-2CP (-3.9 kcal/mol) < DehHsAAD6-2,2-DCP (-3.5 kcal/mol) < DehHsAAD6-3CP (-3.2 kcal/mol). In a nutshell, the study findings offer valuable perceptions into the elucidation of possible reaction mechanisms of dehalogenases for extended substrate specificity and higher catalytic activity.Communicated by Ramaswamy H. Sarma.

Bridging the functional gap between reactivity and inhibition in dehaloperoxidase B from Amphitrite ornata: Mechanistic and structural studies with 2,4- and 2,6-dihalophenols

The multifunctional catalytic globin dehaloperoxidase (DHP) from the marine worm Amphitrite ornata was shown to catalyze the H₂O₂-dependent oxidation of 2,4- and 2,6-dihalophenols (DXP; X = F, Cl, Br). Product identification by LC-MS revealed multiple monomeric products with varying degrees of oxidation and/or dehalogenation, as well as oligomers with n up to 6. Mechanistic and ¹⁸O-labeling studies demonstrated sequential dihalophenol oxidation via peroxidase and peroxygenase activities. Binding studies established that 2,4-DXP (X = Cl, Br) have the highest affinities of any known DHP substrate. X-ray crystallography identified different binding positions for 2,4- and 2,6-DXP substrates in the hydrophobic distal pocket of DHP. Correlation between the number of halogens and the substrate binding orientation revealed a halogen-dependent binding motif for mono- (4-halophenol), di- (2,4- and 2,6-dihalophenol) and trihalophenols (2,4,6-trihalopenol). Taken together, the findings here on dihalophenol reactivity with DHP advance our understanding of how these compounds bridge the inhibitory and oxidative functions of their mono- and trihalophenol counterparts, respectively, and provide further insight into the protein structure-function paradigm relevant to multifunctional catalytic globins in comparison to their monofunctional analogs.

Characterization of DBP precursor removal by magnetic ion exchange resin using spectroscopy and high-resolution mass spectrometry

The characteristics of dissolved organic matter (DOM) play an important role in the formation and speciation of carcinogenic disinfection byproducts. This study investigated changes in the characteristics and reactivity of DOM caused by the magnetic ion exchange resins, MIEX® DOC and MIEX® GOLD, using fluorescence excitation-emission matrix (EEM) with parallel factor (PARAFAC) analysis and Orbitrap mass spectrometry (Orbitrap MS) with unknown screening analysis. A five-component PARAFAC model was developed and validated from 208 EEMs of raw and MIEX®-treated water samples. The two resins exhibited preferential removal of the humic-like components (67-87% removal) and successfully removed protein-like components to a lesser extent (5-61% removal). Unknown screening analysis indicated removal of most condensed aromatic structures and lignin-like features that had high O/C values and refractory characteristics of lipid-like features by MIEX® treatments. MIEX® preferentially removed DOM molecules with more oxidized and shorter CH₂ chains. The two resins had similar performance in trihalomethanes formation potential removal, but MIEX® GOLD achieved greater haloacetonitriles formation potential removal owing to its larger pore opening. Over 100 CHOCl DBP features were commonly found in all the samples while tens of CHOCl DBPs were uniquely formed in the samples with and without pre-treatments by MIEX®. Treatments by MIEX® before chlorination resulted in more intermediate CHOCl DBPs formed after chlorination compared to chlorinated raw waters. By optical spectroscopic analysis together with Orbitrap MS molecular characterization, we were able to confirm both quantitative and qualitative changes in DOM properties by MIEX® treatment related to DBP formation.

Desulfoluna spp. form a cosmopolitan group of anaerobic dehalogenating bacteria widely distributed in marine sponges

Host-specific microbial communities thrive within sponge tissues and this association between sponge and associated microbiota may be driven by the organohalogen chemistry of the sponge animal. Several sponge species produce diverse organobromine secondary metabolites (e.g. brominated phenolics, indoles, and pyrroles) that may function as a chemical defense against microbial fouling, infection or predation. In this study, anaerobic cultures prepared from marine sponges were amended with 2,6-dibromophenol as the electron acceptor and short chain organic acids as electron donors. We observed reductive dehalogenation from diverse sponge species collected at disparate temperate and tropical waters suggesting that biogenic organohalides appear to enrich for populations of dehalogenating microorganisms in the sponge animal. Further enrichment by successive transfers with 2,6-dibromophenol as the sole electron acceptor demonstrated the presence of dehalogenating bacteria in over 20 sponge species collected from temperate and tropical ecoregions in the Atlantic and Pacific Oceans and the Mediterranean Sea. The enriched dehalogenating strains were closely related to Desulfoluna spongiiphila and Desulfoluna butyratoxydans, suggesting a cosmopolitan association between Desulfoluna spp. and various marine sponges. In vivo reductive dehalogenation in intact sponges was also demonstrated. Organobromide-rich sponges may thus provide a specialized habitat for organohalide-respiring microbes and D. spongiiphila and/or its close relatives are responsible for reductive dehalogenation in geographically widely distributed sponge species.

Oxidation of Iodine to Dihaloiodate(I) Salts of Amines With Hydrogen Peroxides and Their Crystal Structures

Herein we report a general preparation of dihaloiodate salts of heterocyclic amines (tertiary and quaternary) with sterically accessible and hindered nitrogen atom. A number of such compounds were prepared from preformed HICl₂ or HIBr₂ formed in situ by the reaction of corresponding hydrogen halide, iodine and H₂O₂. The salts of 1,4-diazabicyclo[2.2.2]octane (DABCO) and its methylated derivatives, 1,3,5,7-tetraazaadamantane (HMTA), diazabicycloundecene (DBU) and 2,4,6-tri-tert-butylpyridine (TBP) were obtained in excellent yields and their structure was determined by NMR and Raman spectroscopy and single crystal X-ray diffraction. Non-hindered bases such as DABCO, HMTA and DBU formed IX₂⁻ salts, which further decomposed to complexes with interhalogen compounds due to formation of N…X halogen bonds. The dihaloiodiate(I) salts of sterically hindered 2,4,6-tri-tert-butylpyridine were stable. Its dichlorobromate(I) salt was also prepared via a different synthetic method using N-chlorosuccinimide as oxidant.

Probing the Electronic Properties and Interaction Landscapes in a Series of N-(Chlorophenyl)pyridinecarboxamides

A 3 × 3 isomer grid of nine N-(chlorophenyl)pyridinecarboxamides (NxxCl) is reported with physicochemical studies and single crystal structures (Nx = pyridinoyl moiety; xCl = aminochlorobenzene ring; x = para-/meta-/ortho-), as synthesized by the reaction of the substituted p-/m-/o-pyridinecarbonyl chlorides (Nx) with p-/m-/o-aminochlorobenzenes (xCl). Several of the nine NxxCl crystal structures display structural similarities with their halogenated NxxX and methylated NxxM relatives (x = p-/m-/o-substitutions; X = F, Br; M = methyl). Indeed, five of the nine NxxCl crystal structures are isomorphous with their NxxBr analogues as the NpmCl/Br, NpoCl/Br, NmoCl/NmoBr, NopCl/Br, and NooCl/Br pairs. In the NxxCl series, the favored hydrogen bonding mode is aggregation by N-H···N_pyridine interactions, though amide···amide intermolecular interactions are noted in NpoCl and NmoCl. For the NoxCl triad, intramolecular N-H···N_pyridine interactions influence molecular planarity, whereas NppCl·H₂O (as a monohydrate) exhibits O-H···O, N-H···O1W, and O1W-H···N interactions as the primary hydrogen bonding. Analysis of chlorine-containing compounds on the CSD is noted for comparisons. The interaction environments are probed using Hirshfeld surface analysis and contact enrichment studies. The melting temperatures (T _m) depend on both the lattice energy and molecular symmetry (Carnelley's rule), and the melting points can be well predicted from a linear regression of the two variables. The relationships of the T _m values with the total energy, the electrostatic component, and the strongest hydrogen bond components have been analyzed.

First report on hydroxylated and methoxylated polybrominated diphenyl ethers in terrestrial environment from the Arctic and Antarctica

Terrestrial plants, which account for the world's largest biomass and constitute the basis of most food webs, take up, transform, and accumulate organic chemical contaminants from the ambient environment. In this study, we determined the concentrations and congener profiles of polybrominated diphenyl ethers (PBDEs) and hydroxylated and methoxylated polybrominated diphenyl ethers (OH-PBDEs and MeO-PBDEs) in surface soil and vegetation samples collected from the Arctic (Svalbard) and Antarctica (King George Island) during the Chinese Scientific Research Expeditions. The concentrations of total PBDEs (∑PBDEs) in soil and vegetation samples collected from the Arctic (5.6-270 pg/g dry weight) were higher than those from Antarctica (2.3-33 pg/g dw), whereas the concentrations of ∑MeO-PBDEs and ∑OH-PBDEs were lower in Arctic terrestrial samples (n.d.-0.75 and 0.0008-1.1 ng/g dw, respectively) than in samples from Antarctica (0.007-4.0 and 0.034-25 ng/g dw, respectively). Long-range atmospheric transport and human activities were potential sources of PBDEs in polar regions, whereas the dominance of ortho-substituted MeO-PBDE and OH-PBDE congeners in terrestrial matrices indicated the importance of natural sources. To the best of our knowledge, this study represents the first report on the levels and behaviors of MeO-PBDEs and OH-PBDEs in terrestrial environment of polar regions.

超声提取-高温燃烧吸收-离子色谱法测定纺织品中可吸附有机卤化物

建立了一种对纺织品中可吸附有机卤化物(AOX)的超声提取-高温燃烧吸收-离子色谱定量检测分析新方法。该方法采用超声方式提取纺织品中的AOX,提取液加入活性炭进行振荡吸附,并用酸性硝酸钠溶液对无机卤化物进行去除。采用程序升温的氧化燃烧方式对吸附AOX的活性炭进行裂解、燃烧及气化,其产生的卤化氢等气体随载气进入吸收液并完全转化为无机卤素阴离子,采用离子色谱分离测定,外标法定量。实验优化了超声提取时间、活性炭用量、燃烧气及其流量、燃烧升温程序、吸收液和吸收方式等前处理条件,并对离子色谱的仪器分析条件如色谱柱、柱温及淋洗液流速等进行优化。结果表明,氟、氯、溴、碘4种卤素离子的标准溶液在0.02~10 mg/L范围内呈线性关系,线性相关系数(R²)均在0.999以上;AOX测定的方法定量限为0.10~0.50 mg/kg。以棉、毛和涤纶3种不同种类的阴性纺织样品作为样品基质,选取典型的有机卤化物进行加标,在低、中、高3个加标水平下测得AOX的平均回收率为82.3%~98.7%,相对标准偏差(RSD, n=7)为2.0%~5.7%,表明方法具有良好的回收率和精密度。将该方法应用于实际纺织样品的测定,检出了不同含量的AOX,且重复性好。研究建立的方法通过采用活性炭的振荡吸附、程序升温的高温氧化燃烧方式和多孔吸收瓶的二级吸收方法,提高了AOX转化为无机卤素的回收率;同时利用离子色谱仪器选择性好、灵敏度高的特点成功地一次性分离检测4种AOX,且无杂质离子的干扰。该方法简单、准确、可靠,满足国内外法规和标准对纺织品中AOX的限量要求,适用于纺织品中AOX的分析测定。

Characterization of Halogenated Organic Compounds in Pelagic Sharks and Sea Turtles Using a Nontargeted Approach

Halogenated organic compounds (HOCs) in marine species collected from the Atlantic Ocean [3 shortfin mako (Isurus oxyrinchus) and 1 porbeagle (Lamna nasus)], and 12 sea turtles collected from the Pacific Ocean [3 loggerhead (Caretta caretta), 3 green (Chelonia mydas), 3 olive ridley (Lepidochelys olivacea), and 3 hawksbill (Eretmochelys imbricata)] were analyzed with a nontargeted analytical method using two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry. Sharks and sea turtles had distinct HOC profiles. Halogenated methoxyphenols (halo-MeOPs) were the most abundant compound class identified in sea turtle livers, while polychlorinated biphenyls (PCBs) were the most abundant in shark livers. In addition to legacy contaminants and halo-MeOPs, a total of 110 nontargeted/novel HOCs (NHOCs) were observed in the shark livers. Shortfin mako collected from the northern Gulf of Mexico contained the largest number (89) and most diverse structural classes of NHOCs. Among all NHOCs, a group of compounds with the elemental composition C₁₄H_12-nCl_n (n = 5-8) exhibited the highest concentrations, followed by chlorocarbazoles and tris(chlorophenyl) methanes (TCPMs). Using nontargeted workflows, a variety of known and unknown HOCs were observed, which demonstrate the need to develop more complete chemical profiles in the marine environment.

The Electrochemical cis-Chlorination of Alkenes

The first example for the electrochemical cis‐dichlorination of alkenes is presented. The reaction can be performed with little experimental effort by using phenylselenyl chloride as catalyst and tetrabutylammoniumchloride as supporting electrolyte, which also acts as nucleophilic reagent for the S_N2‐type replacement of selenium versus chloride. Cyclic voltammetric measurements and control experiments revealed a dual role of phenylselenyl chloride in the reaction. Based on these results a reaction mechanism was postulated, where the key step of the process is the activation of a phenylselenyl chloride‐alkene adduct by electrochemically generated phenylselenyl trichloride. Like this, different aliphatic and aromatic cyclic and acyclic alkenes were converted to the dichlorinated products. Thereby, throughout high diastereoselectivities were achieved for the cis‐chlorinated compounds of >95 : 5 or higher.

Fast isolation of the environmentally relevant halogenated natural product MHC-1 by means of countercurrent chromatography

Environmentally relevant halogenated natural products (HNPs) are frequently similarly high concentrated in marine biota as major anthropogenic persistent organic pollutants (POPs). The lack of widely available reference standards, however, hampers the in-depth research of several HNPs. For instance, (1R,2S,4R,5R,1'E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(2'-chloroethenyl)-5-methylcyclohexane (MHC-1), which is produced by species referred to the red seaweed Plocamium cartilagineum has not yet been synthesized due to its complex structure and stereochemistry. For this reason, we aimed to establish a method for fast isolation of mg-amounts of MHC-1 from its natural producer based on countercurrent chromatography (CCC). Five biphasic solvent systems were tested and finally, the solvent system acetonitrile/n-hexane/toluene (9:9:2, v/v/v) was selected for the separations due to its suitable partition coefficient of MHC-1 (K_U/L = 0.52). n-Hexane extracts of dried P. cartilagineum were directly injected into the CCC system. Four subsequent CCC runs from three samples of Plocamium cartilagineum (two from Heligoland, Germany and one from Brittany, France) could be performed with high reproducibility. Together, the main fraction provided ~16 mg MHC-1 in a purity of >97% according to GC/FID, GC/ECNI-MS and NMR analysis. This amount could be used to prepare ~1600 quantitative standard solutions of MHC-1. The high MHC-1 content in the seaweed sample collected at Brittany indicated that this area was another hotspot of MHC-1.

Chlorinated bisabolene sesquiterpenoids from the whole plant of Parasenecio rubescens

Four new chlorinated bisabolene-type sesquiterpenoids (1-4) were isolated during the phytochemical investigation of an acetone extract of the whole plant of Parasenecio rubescens. The structures of 1-4 were determined by analysis of their HRESIMS and NMR spectroscopic data, and the absolute configuration of 1 was established through single-crystal X-ray diffraction. All isolates were evaluated for their cytotoxicity against three cancer cell lines (B16 mouse melanoma, HepG2 human hepatocellular carcinoma, and MCF7 human breast adenocarcinoma), as well as their antimicrobial effects against Staphylococcus aureus, Escherichia coli, and Monilia albicans. As a result, compounds 1-4 displayed a certain degree of antimicrobial activities.

Identification of novel halogenated naturally occurring compounds in marine biota by high-resolution mass spectrometry and combined screening approaches

Marine animals, plants or bacteria are a source of bioactive naturally-occurring halogenated compounds (NHCs) such as bromophenols (BPs), bromoanisoles (BAs) and hydroxylated or methoxylated analogues of polybrominated diphenyl ethers (HO-PBDEs, MeO-PBDEs) and bromobiphenyls (HO-BBs, MeO-BBs). This study applied a comprehensive screening approach using liquid chromatography high-resolution mass spectrometry and combining target, suspect and non-target screening with the aim to identify new hydroxylated NHCs which might be missed by commonly applied gas chromatographic methods. 24 alga samples, 4 sea sponge samples and 7 samples of other invertebrates were screened. Target screening was based on 19 available reference standards of BPs, (di)OH-BDEs and diOH-BBs and yielded seven unequivocally identified compounds. 6-OH-BDE47 was the most frequently detected compound with a detection frequency of 31%. Suspect screening yielded two additional compounds identified in alga samples as well as 17 and 8 compounds identified in sea sponge samples of Lamellodysidea sp. and Callyspongia sp., respectively. The suspect screening results presented here confirmed the findings of previous studies conducted on sea sponge samples of Lamellodysidea sp. and Callyspongia sp. Additionally, in Lamellodysidea sp. and Callyspongia sp. 13 and 4 newly identified NHCs are reported including heptabrominated diOH-BDE, monochlorinated pentabrominated diOH-BDE, hexabrominated OH-MeO-BDE and others. Non-target screening allowed the identification of 31 and 20 polyhalogenated compounds in Lamellodysidea sp. and Callyspongia sp. samples, respectively. Based on the obtained fragmentation spectra, polybrominated dihydroxylated diphenoxybenzenes (diOH-PBDPBs), such as hepta-, octa- and nonabrominated diOH-BDPBs, could be identified in both species. To our knowledge, this study is the first report on the environmental presence of OH-PBDPBs.

Functional Characterization of a L-2-Haloacid Dehalogenase From Zobellia galactanivorans DsijT Suggests a Role in Haloacetic Acid Catabolism and a Wide Distribution in Marine Environments

L-2-halocid dehalogenases (L-2-HADs) have been mainly characterized from terrestrial polluted environments. By contrast, knowledge is still scarce about their role in detoxification of predominant halocarbons in marine environments. Here, phylogenetic analyses showed a wide diversity of homologous L-2-HADs, especially among those belonging to marine bacteria. Previously characterized terrestrial L-2-HADs were part of a monophyletic group (named group A) including proteins of terrestrial and marine origin. Another branch (named group B) contained mostly marine L-2-HADs, with two distinct clades of Bacteroidetes homologs, closely linked to Proteobacteria ones. This study further focused on the characterization of the only L-2-HAD from the flavobacterium Zobellia galactanivorans Dsij^T (ZgHAD), belonging to one of these Group B clades. The recombinant ZgHAD was shown to dehalogenate bromo- and iodoacetic acids, and gene knockout in Z. galactanivorans revealed a direct role of ZgHAD in tolerance against both haloacetic acids. Analyses of metagenomic and metatranscriptomic datasets confirmed that L-2-HADs from group A were well-represented in terrestrial and marine bacteria, whereas ZgHAD homologs (group B L-2-HADs) were mainly present in marine bacteria, and particularly in host-associated species. Our results suggest that ZgHAD homologs could be key enzymes for marine Bacteroidetes, by conferring selective advantage for the recycling of toxic halogen compounds produced in particular marine habitats, and especially during interactions with macroalgae.

Asparagopsis armata Exudate Cocktail: The Quest for the Mechanisms of Toxic Action of an Invasive Seaweed on Marine Invertebrates

Simple Summary

The invasive red seaweed Asparagopsis armata exhibits a strong invasive behavior, producing harmful secondary metabolites that negatively affect the surrounding community. This study addressed the antioxidant defenses, oxidative damage, and a neuronal parameter, as well as the fatty acid composition responses to sublethal concentrations of A. armata released compounds on the marine snail Gibbula umbilicalis and the shrimp Palaemon serratus. Results revealed that the test species had different metabolic responses to the A. armata exudate concentrations tested. Impacts in G. umbilicalis does not seem to arise from oxidative stress or neurotoxicity, while for P. elegans, an inhibition of AChE and the decrease of antioxidant capacity and increase of LPO suggest neurotoxicity and oxidative stress as contributing to the observed toxicity. Additionally, there were different fatty acid profile changes between species, but omega-3 PUFAs ARA and DPA increased in both invertebrates, indicating a common regulation mechanism of inflammation and immunity responses.

Abstract

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.

Extractable organochlorine (EOCl) and extractable organobromine (EOBr) in GPC-fractionated extracts from high-trophic-level mammals: Species-specific profiles and contributions of legacy organohalogen contaminants

Previous studies have suggested that unidentified compounds constitute a large proportion of extractable organochlorine (EOCl) and extractable organobromine (EOBr) in the crude extracts without fractionation; however, the proportion of unidentified EOX (X = chlorine, bromine) associated with high-/low-molecular-weight compounds is still unknown. In this study, we applied gel permeation chromatography to fractionate extracts from archived liver samples of high-trophic marine and terrestrial mammals (striped dolphins, cats, and raccoon dogs), for which concentrations of legacy organohalogen contaminants (polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers [PBDEs]) had been previously reported. EOX in high- (>1000 g/mol) and low- (≤1000 g/mol) molecular-weight fractions (EOX-H and EOX-L) were determined by neutron activation analysis. Comparison of EOCl and EOBr enabled the characterization among species. Despite small differences in the concentrations and molecular-weight profiles of EOCl among species, the contribution of chlorine in identified compounds to EOCl-L varied from 1.5% (cats) to 79% (striped dolphins). Considerable species-specific variations were observed in the concentrations of EOBr: striped dolphins exhibited significantly greater concentrations of both EOBr-H and EOBr-L than cats and/or raccoon dogs. Moreover, the contribution of bromine in PBDEs to EOBr-L was >50% in two cats, while it was <6% in other specimens. This is the first report on EOBr mass balance in cetaceans and on EOX mass balance in terrestrial mammals living close to humans. These results suggest the need for analysis of unidentified chlorinated compounds in terrestrial mammals and unidentified brominated compounds in marine mammals.

Insights into phenolic compounds from microalgae: structural variety and complex beneficial activities from health to nutraceutics

Phenolic compounds (PCs) are a family of secondary metabolites with recognized biological activities making them attractive for the biomedical "red" biotechnology. The development of the eco-sustainable production of natural bioactive metabolites requires using easy cultivable organisms, such as microalgae, which represents one of the most promising sources for biotechnological applications. Microalgae are photosynthetic organisms inhabiting aquatic systems, displaying high levels of biological and functional diversities, and are well-known producers of fatty acids and carotenoids. They are also rich in other families of bioactive molecules e.g. phenolic compounds. Microalgal PCs however are less investigated than other molecular components. This study aims to provide a state-of-art picture of the actual knowledge on microalgal phenolic compounds, reviewing information on the PC content variety and chemodiversity in microalgae, their environmental modulation, and we aim to report discuss data on PC biosynthetic pathways. We report the challenges of promoting microalgae as a relevant source of natural PCs, further enhancing the interests of microalgal "biofactories" for biotechnological applications (i.e. nutraceutical, pharmacological, or cosmeceutical products).

Chlorine cycling and the fate of Cl in terrestrial environments

Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; 36Cl is of large concern) and plant science (Cl as essential element for living plants). During the past decades, there has been a rapid development towards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Clorg) in soil frequently exceed the abundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Clorg and biomass Cl can dominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting in prolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Cl cycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing the main Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is a production of Clorg in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms. Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce, and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.

Simultaneous determination of stable chlorine and bromine isotopic ratios for bromochlorinated trihalomethanes using GC-qMS

Bromochlorinated compounds are organic contaminants originating from different natural and anthropic sources and increasingly found in different environmental compartments. This work presents an online approach for compound specific stable isotope analysis of chlorine and bromine isotope ratios for bromochlorinated trihalomethanes using gas chromatography coupled to quadrupole mass spectrometry (GC-qMS). An evaluation scheme was developed to simultaneously determine stable chlorine and bromine isotope ratios based on the mass spectral data of two target compounds: dibromochloromethane and dichlorobromomethane. The analytical technique was optimized by assessing the impact of different instrumental parameters, including dwell time, split ratios, and ionization energy. Successively, static headspace samples containing the two target compounds at aqueous concentrations ranging from 0.1 mg/L to 5 mg/L were analyzed in order to test the precision and reproducibility of the proposed approach. The results showed a good precision under the optimized instrumental conditions, with relative standard deviations ranging between 0.05% and 0.5% for chlorine and bromine isotope analysis. Finally, the method was tested in a source identification problem in which the simultaneous determination of chlorine and bromine stable isotope ratios allowed the clear distinction of dibromochloromethane from three different manufacturers.

Humic Acid Extracts Leading to the Photochemical Bromination of Phenol in Aqueous Bromide Solutions: Influences of Aromatic Components, Polarity and Photochemical Activity

Dissolved organic matter (DOM) is considered to play an important role in the abiotic transformation of organobromine compounds in marine environment, for it produces reactive intermediates photochemically and is recognized as a significant source of reactive halogen species in seawater. However, due to the complex composition of DOM, the relationship between the natural properties of DOM and its ability to produce organobromine compounds is less understood. Here, humic acid (HA) was extracted and fractionated based on the polarity and hydrophobicity using silica gel, and the influences of different fractions (F_A, F_B and F_C) on the photochemical bromination of phenol was investigated. The structural properties of HA fractions were characterized by UV-vis absorption, Fourier transform infrared spectroscopy and fluorescence spectroscopy, and the photochemical reactivity of HA fractions was assessed by probing triplet dissolved organic matter (³DOM*), singlet oxygen (¹O₂) and hydroxyl radical (^•OH). The influences of HA fractions on the photo-bromination of phenol were investigated in aqueous bromide solutions under simulated solar light irradiation. F_A and F_B with more aromatic and polar contents enhanced the photo-bromination of phenol more than the weaker polar and aromatic F_C. This could be attributed to the different composition and chemical properties of the three HAs’ fractions and their production ability of ^•OH and ³DOM*. Separating and investigating the components with different chemical properties in DOM is of great significance for the assessment of their environmental impacts on the geochemical cycle of organic halogen.

A Review: Halogenated Compounds from Marine Fungi

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.

Biodegradation of dioxins by Burkholderia cenocepacia strain 869T2: Role of 2-haloacid dehalogenase

Dioxin compounds are persistent carcinogenic byproducts of anthropogenic activities such as waste combustion and other industrial activities. The ubiquitous distribution of dioxins is global concerns these days. Among of recent techniques, bioremediation, an eco-friendly and cost-effective technology, uses bacteria or fungi to detoxify in dioxins; however, not many bacteria can degrade the most toxic dioxin congener 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD). In this study, the endophytic bacterium Burkholderia cenocapacia 869T2 was capable of TCDD degradation by nearly 95 % after one-week of an aerobic incubation. Through transcriptomic analysis of the strain 869T2 at 6 -h and 12 -h TCDD exposure, a number of catabolic genes involved in dioxin metabolism were detected with high gene expressions in the presence of TCDD. The transcriptome data also indicated that B. cenocepacia strain 869T2 metabolized the dioxin compounds from an early phase (at 6 h) of the incubation, and the initial outline for a general dioxin degradation pathway were proposed. One of the catabolic genes, l-2-haloacid dehalogenase (2-HAD) was cloned to investigate its contribution in dioxin dehalogenation. By detecting the increasing concentration of chloride ions released from TCDD, our results indicated that the dehalogenase played a crucial role in dehalogenation of dioxin in the aerobic condition.

C–H hetero-functionalization of arenes through palladacyclopentane-type intermediates

In this review article, we summarized recent advances in C–H hetero-functionalization of arenes through palladacyclopentane-type intermediates.

Functional characterisation of the transcriptome from leaf tissue of the fluoroacetate-producing plant, Dichapetalum cymosum, in response to mechanical wounding

Dichapetalum cymosum produces the toxic fluorinated metabolite, fluoroacetate, presumably as a defence mechanism. Given the rarity of fluorinated metabolites in nature, the biosynthetic origin and function of fluoroacetate have been of particular interest. However, the mechanism for fluorination in D. cymosum was never elucidated. More importantly, there is a severe lack in knowledge on a genetic level for fluorometabolite-producing plants, impeding research on the subject. Here, we report on the first transcriptome for D. cymosum and investigate the wound response for insights into fluorometabolite production. Mechanical wounding studies were performed and libraries of the unwounded (control) and wounded (30 and 60 min post wounding) plant were sequenced using the Illumina HiSeq platform. A combined reference assembly generated 77,845 transcripts. Using the SwissProt, TrEMBL, GO, eggNOG, KEGG, Pfam, EC and PlantTFDB databases, a 69% annotation rate was achieved. Differential expression analysis revealed the regulation of 364 genes in response to wounding. The wound responses in D. cymosum included key mechanisms relating to signalling cascades, phytohormone regulation, transcription factors and defence-related secondary metabolites. However, the role of fluoroacetate in inducible wound responses remains unclear. Bacterial fluorinases were searched against the D. cymosum transcriptome but transcripts with homology were not detected suggesting the presence of a potentially different fluorinating enzyme in plants. Nevertheless, the transcriptome produced in this study significantly increases genetic resources available for D. cymosum and will assist with future research into fluorometabolite-producing plants.

Dehalogenase-producing halophiles and their potential role in bioremediation

This review aims to briefly describe the potential role of dehalogenase-producing halophilic bacteria in decontamination of organohalide pollutants. Hypersaline habitats pose challenges to life because of low water activity (water content) and is considered as the largest and ultimate sink for pollutants due to naturally and anthropogenic activities in which a substantial amount of ecological contaminants are organohalides. Several such environments appear to host and support substantial diversity of extremely halophilic and halotolerant bacteria as well as halophilic archaea. Biodegradation of several toxic inorganic and organic compounds in both aerobic and anaerobic conditions are carried out by halophilic microbes. Therefore, remediation of polluted marine/hypersaline environments are the main scorching issues in the field of biotechnology. Although many microbial species are reported as effective pollutants degrader, but little has been isolated from marine/hypersaline environments. Therefore, more novel microbial species with dehalogenase-producing ability are still desired.

Deploying Microbial Synthesis for Halogenating and Diversifying Medicinal Alkaloid Scaffolds

Plants produce some of the most potent therapeutics and have been used for thousands of years to treat human diseases. Today, many medicinal natural products are still extracted from source plants at scale as their complexity precludes total synthesis from bulk chemicals. However, extraction from plants can be an unreliable and low-yielding source for human therapeutics, making the supply chain for some of these life-saving medicines expensive and unstable. There has therefore been significant interest in refactoring these plant pathways in genetically tractable microbes, which grow more reliably and where the plant pathways can be more easily engineered to improve the titer, rate and yield of medicinal natural products. In addition, refactoring plant biosynthetic pathways in microbes also offers the possibility to explore new-to-nature chemistry more systematically, and thereby help expand the chemical space that can be probed for drugs as well as enable the study of pharmacological properties of such new-to-nature chemistry. This perspective will review the recent progress toward heterologous production of plant medicinal alkaloids in microbial systems. In particular, we focus on the refactoring of halogenated alkaloids in yeast, which has created an unprecedented opportunity for biosynthesis of previously inaccessible new-to-nature variants of the natural alkaloid scaffolds.

The Potential for Bio-Sustainable Organobromine-Containing Flame Retardant Formulations for Textile Applications-A Review

This review considers the challenge of developing sustainable organobromine flame retardants (BrFRs) and alternative synergists to the predominantly used antimony III oxide. Current BrFR efficiencies are reviewed for textile coatings and back-coatings with a focus on furnishing and similar fabrics covering underlying flammable fillings, such as flexible polyurethane foam. The difficulty of replacing them with non-halogen-containing systems is also reviewed with major disadvantages including their extreme specificity with regard to a given textile type and poor durability.The possibility of replacing currently used BrFRs for textiles structures that mimic naturally occurring organobromine-containing species is discussed, noting that of the nearly 2000 such species identified in both marine and terrestrial environments, a significant number are functionalised polybrominated diphenyl ethers, which form part of a series of little understood biosynthetic biodegradation cycles.The continued use of antimony III oxide as synergist and possible replacement by alternatives, such as the commercially available zinc stannates and the recently identified zinc tungstate, are discussed. Both are effective as synergists and smoke suppressants, but unlike Sb₂0₃, they have efficiencies dependent on BrFR chemistry and polymer matrix or textile structure. Furthermore, their effectiveness in textile coatings has yet to be more fully assessed.In conclusion, it is proposed that the future of sustainable BrFRs should be based on naturally occurring polybrominated structures developed in conjunction with non-toxic, smoke-suppressing synergists such as the zinc stannates or zinc tungstate, which have been carefully tailored for given polymeric and textile substrates.

Uptake, phytovolatilization, and interconversion of 2,4-dibromophenol and 2,4-dibromoanisole in rice plants

The structural analogs, 2,4-dibromophenol (2,4-DBP) and 2,4-dibromoanisole (2,4-DBA), have both natural and artificial sources and are frequently detected in environmental matrices. Their environmental fates, especially volatilization, including both direct volatilization from cultivation solution and phytovolatilization through rice plants were evaluated using hydroponic exposure experiments. Results showed that 2,4-DBA displayed stronger volatilization tendency and more bioaccumulation in aboveground rice tissues. Total volatilized 2,4-DBA accounted for 4.74% of its initial mass and was 3.43 times greater than 2,4-DBP. Phytovolatilization of 2,4-DBA and 2,4-DBP contributed to 6.78% and 41.7% of their total volatilization, enhancing the emission of these two contaminants from hydroponic solution into atmosphere. In this study, the interconversion processes between 2,4-DBP and 2,4-DBA were first characterized in rice plants. The demethylation ratio of 2,4-DBA was 12.0%, 32.0 times higher than methylation of 2,4-DBP. Formation of corresponding metabolites through methylation and demethylation processes also contributed to the volatilization of 2,4-DBP and 2,4-DBA from hydroponic solution into the air phase. Methylation and demethylation processes increased phytovolatilization by 12.1% and 36.9% for 2,4-DBP and 2,4-DBA. Results indicate that phytovolatilization and interconversion processes in rice plants serve as important pathways for the global cycles of bromophenols and bromoanisoles.

Rapid Killing and Biofilm Inhibition of Multidrug-Resistant Acinetobacter baumannii Strains and Other Microbes by Iodoindoles

Multi-drug resistant Acinetobacter baumannii is well-known for its rapid acclimatization in hospital environments. The ability of the bacterium to endure desiccation and starvation on dry surfaces for up to a month results in outbreaks of health care-associated infections. Previously, indole and its derivatives were shown to inhibit other persistent bacteria. We found that among 16 halogenated indoles, 5-iodoindole swiftly inhibited A. baumannii growth, constrained biofilm formation and motility, and killed the bacterium as effectively as commercial antibiotics such as ciprofloxacin, colistin, and gentamicin. 5-Iodoindole treatment was found to induce reactive oxygen species, resulting in loss of plasma membrane integrity and cell shrinkage. In addition, 5-iodoindole rapidly killed three Escherichia coli strains, Staphylococcus aureus, and the fungus Candida albicans, but did not inhibit the growth of Pseudomonas aeruginosa. This study indicates the mechanism responsible for the activities of 5-iodoindole warrants additional study to further characterize its bactericidal effects on antibiotic-resistant A. baumannii and other microbes.

Structural and Bioactive Studies of Halogenated Constituents from Sponges

Marine organisms are abundant sources of bioactive natural products. Among metabolites produced by sponges and their associated microbial communities, halogenated natural compounds accounted for an important part due to their potent biological activities. The present review updates and compiles a total of 258 halogenated organic compounds isolated in the past three decades, especially brominated derivatives derived from 31 genera of marine sponges. These compounds can be classified as the following classes: brominated polyunsaturated lipids, nitrogen compounds, brominated tyrosine derivatives and other halogenated compounds. These substances were listed together with their source organisms, structures and bioactivities. For this purpose, 84 references were consulted.

Will Climate Change Influence Production and Environmental Pathways of Halogenated Natural Products?

Thousands of halogenated natural products (HNPs) pervade the terrestrial and marine environment. HNPs are generated by biotic and abiotic processes and range in complexity from low molecular mass natural halocarbons (nHCs, mostly halomethanes and haloethanes) to compounds of higher molecular mass which often contain oxygen and/or nitrogen atoms in addition to halogens (hHNPs). nHCs have a key role in regulating tropospheric and stratospheric ozone, while some hHNPs bioaccumulate and have toxic properties similar those of anthropogenic-persistent organic pollutants (POPs). Both chemical classes have common sources: biosynthesis by marine bacteria, phytoplankton, macroalgae, and some invertebrate animals, and both may be similarly impacted by alteration of production and transport pathways in a changing climate. The nHCs scientific community is advanced in investigating sources, atmospheric and oceanic transport, and forecasting climate change impacts through modeling. By contrast, these activities are nascent or nonexistent for hHNPs. The goals of this paper are to (1) review production, sources, distribution, and transport pathways of nHCs and hHNPs through water and air, pointing out areas of commonality, (2) by analogy to nHCs, argue that climate change may alter these factors for hHNPs, and (3) suggest steps to improve linkage between nHCs and hHNPs science to better understand and predict climate change impacts.

Diverse dechlorinators and dechlorination genes enriched through amendment of chlorinated natural organic matter fractions

In uncontaminated environments, chlorinated natural organic matter (Cl-NOM) can act as an electron acceptor for organohalide-respiring bacteria. It is unknown, however, whether different types of Cl-NOM are preferentially dechlorinated or whether enrichment with Cl-NOM affects the ability of bacteria to dechlorinate contaminants. In this research NOM was extracted from sediment, fractionated based on hydrophobicity, and either amended to polychlorinated biphenyl-contaminated soil directly or chlorinated and then amended to soil. Amendments of the least hydrophobic Cl-NOM fraction were dechlorinated most rapidly, followed by the moderately hydrophobic Cl-NOM fraction. Soil that had been enriched on the moderately hydrophobic fraction of Cl-NOM was also capable of faster dechlorination of the contaminants trichloroethene and tetrachlorobenzene. Community analysis of the soil during enrichment showed that some known organohalide-respiring bacteria were present and may have played a role in dechlorination; nevertheless, many bacteria appeared to be enriched during both Cl-NOM and contaminant dechlorination. In addition, the quantities of two haloalkane dehalogenase genes increased during enrichment on Cl-NOM. These results show for the first time that Cl-NOM can prime contaminant dechlorination and also suggest that hydrolytic dechlorination processes were involved in both Cl-NOM and contaminant dechlorination.

Monooxygenation of aromatic compounds by flavin-dependent monooxygenases

Many flavoenzymes catalyze hydroxylation of aromatic compounds especially phenolic compounds have been isolated and characterized. These enzymes can be classified as either single-component or two-component flavin-dependent hydroxylases (monooxygenases). The hydroxylation reactions catalyzed by the enzymes in this group are useful for modifying the biological properties of phenolic compounds. This review aims to provide an in-depth discussion of the current mechanistic understanding of representative flavin-dependent monooxygenases including 3-hydroxy-benzoate 4-hydroxylase (PHBH, a single-component hydroxylase), 3-hydroxyphenylacetate 4-hydroxylase (HPAH, a two-component hydroxylase), and other monooxygenases which catalyze reactions in addition to hydroxylation, including 2-methyl-3-hydroxypyridine-5-carboxylate oxygenase (MHPCO, a single-component enzyme that catalyzes aromatic-ring cleavage), and HadA monooxygenase (a two-component enzyme that catalyzes additional group elimination reaction). These enzymes have different unique structural features which dictate their reactivity toward various substrates and influence their ability to stabilize flavin intermediates such as C4a-hydroperoxyflavin. Understanding the key catalytic residues and the active site environments important for governing enzyme reactivity will undoubtedly facilitate future work in enzyme engineering or enzyme redesign for the development of biocatalytic methods for the synthesis of valuable compounds.

Exposure to chemicals formed from natural processes is ubiquitous

Exposure to chemicals produced by natural processes is ubiquitous. First, in addition to the products of normal metabolism produced in humans of normal body weight, adipose tissue produces a large number of chemicals, including estrogen, testosterone from the produced estrogen, thyroid-stimulating hormone, leptin and approximately 500 other molecules termed adipokines, and a large number of inflammatory mediators. Second, the gut biome contains approximately the same number of bacteria as cells found in the entire body and produces a large number of small molecules. Third, the overwhelming majority (99.9%) of pesticide exposure occurs during ingestion of natural plant pesticides from eating vegetables. Fourth, consumption of cooked muscles meats leads to significant exposure to mutagenic and carcinogenic heterocyclic amines, polycyclic aromatic amines, and nitropyrenes. Fifth, many common beverages, for example, beer, coffee, and tea contain organic chemicals that display mutagenic activity. As compared with man-made production levels, from 1945 to 2015, an estimated 5000-fold more organic compounds were produced by a variety of natural processes, including common wood-degrading and forest litter-degrading fungi, microorganisms in temperate and boreal forest soils, bacteria in marine sponges, marine macro-algae, volcanoes, and forest fires. Exposure to these naturally produced organic compounds occurs via inhalation of ambient air, ingestion of food and water, and contact with soil, freshwater, and seawater. Contact with several thousand different endogenous or exogenous chemicals per day is unavoidable. This understanding might assist in better allocating resources toward controlling exposures to agents of highest concern as determined by current concepts of chronic disease causation.