Characterization of 2-phenanthroate:CoA ligase from the sulfate-reducing, phenanthrene-degrading enrichment culture TRIP.

Polycyclic aromatic hydrocarbons (PAHs) are chemically stable pollutants that are poorly degraded by microorganisms in anoxic sediments. The anaerobic degradation pathway of PAHs such as phenanthrene starts with a carboxylation reaction forming phenanthroic acid. In this study, we identified and characterized the next enzyme in the pathway, the 2-phenanthroate:CoA ligase involved in the ATP-dependent formation of 2-phenanthroyl-CoA from cell-free extracts of the sulfate-reducing enrichment culture TRIP grown anaerobically with phenanthrene. The identified gene sequence indicated that 2-phenanthroate:CoA ligase belongs to the phenylacetate:CoA ligase-like enzyme family. Based on the sequence, we predict a two-domain structure of the 2-phenanthroate:CoA ligase with a typical large N-terminal and a smaller C-terminal domain. Partial purification of 2-phenanthroate:CoA ligase allowed us to identify the coding gene in the genome. 2-Phenanthroate:CoA ligase gene was heterologously expressed in Escherichia coli. Characterization of the 2-phenanthroate:CoA ligase was performed using the partially purified enzyme from cell-free extract and the purified recombinant enzyme. Testing all possible phenanthroic acid isomers as substrate for the ligase reaction showed that 2-phenanthroic acid is the preferred substrate and only 3-phenanthroic acid can be utilized to a minor extent. This also suggests that the product of the prior carboxylase reaction is 2-phenanthroic acid. 2-Phenanthroate:CoA ligase has an optimal activity at pH 7.5 and is oxygen-insensitive, analogous to other aryl-CoA ligases. In contrast to aryl-Coenzyme A ligases reported in the literature, which need Mg2+ as cofactor, 2-phenanthroate:CoA ligase showed greatest activity with a combination of 5 mM MgCl2 and 5 mM KCl. Furthermore, a substrate inhibition was observed at ATP concentrations above 1 mM and the enzyme was also active with ADP. IMPORTANCE: Polycyclic aromatic hydrocarbons (PAHs) constitute a class of very toxic and persistent pollutants in the environment. However, the anaerobic degradation of three-ring PAHs such as phenanthrene is barely investigated. The initial degradation step starts with a carboxylation followed by a CoA­thioesterification reaction performed by an aryl-CoA ligase. The formation of a CoA-thioester is an important step in the degradation pathway of aromatic compounds because the CoA-ester is needed for all downstream biochemical reactions in the pathway. Furthermore, we provide biochemical proof for the identification of the first genes for anaerobic phenanthrene degradation. Results presented here provide information about the biochemical and structural properties of the purified 2­phenanthroate:CoA ligase and expand our knowledge of aryl-CoA ligases.

The key monooxygenase involved in phenanthrene degradation of Ruegeria sp. PrR005.

As a typical polycyclic aromatic hydrocarbon (PAH), phenanthrene is often present in diverse environments, leading to severe environmental contamination. However, bacterial degradation plays a crucial role in remediating phenanthrene contamination and has been widely adopted. The widely distributed marine Roseobacter-clade bacteria are frequently found in phenanthrene-contaminated environments, but their catalyzing ability and related molecular mechanism have been rarely elucidated. Our previous work showed Ruegeria sp. PrR005 isolated from the Pearl River Estuary sediment could degrade phenanthrene and other PAHs. Integrated approaches including multi-omics and biochemical analysis were applied here to explore its catabolism mechanism. The genomic and transcriptomic analysis indicated that six new P450 monooxygenase proteins could be closely associated with phenanthrene degradation. Heterologous expression of P450 monooxygenase candidates revealed that PrR005_00615, PrR005_04282, PrR005_04577 have considerable activity in phenanthrene removal, with PrR005_00615 being the primary contributor. Further, the biochemical and metabolic analysis revealed that PrR005_00615 could catalyze phenanthrene to phenanthrene-9,10-epoxide by introducing an oxygen atom at 9,10-carbon positions, which functioned as a monooxygenase. The present study provides compelling evidences of a novel enzyme responsible for catalyzing the initial step of phenanthrene transformation in PrR005. These findings hold significant importance in unraveling the mechanism behind phenanthrene degradation by Roseobacter-clade bacteria.

Metabolic profile changes of zebrafish larvae in the single- and co-exposures of microplastics and phenanthrene.

Microplastics (MPs) are ubiquitous in the environment, and can adsorb organic contaminants (OCs) and be taken by various microorganisms and organisms, which could eventually lead to risk to humans. In this study, the phenotypic changes and metabolic profile alternations of zebrafish in the single- and co-exposure of MPs and phenanthrene (Phe) were investigated. The results showed that significantly higher tail malformation rate and edema rate in zebrafish induced by MPs can be enhanced due to the co-existence of Phe. The metabolomic analysis revealed that both synergistic and antagonistic effects of MPs and Phe on the metabolic alternation of zebrafish larvae exist, since unique perturbations of metabolites or pathways were found in all of the three exposure scenarios. Based on Partial least squares-discriminant analysis, porphine, ribose, and L-glutamic acid were the most important metabolites resulting in the difference between the treated and control groups in the MP exposure, Phe exposure and co-exposure, respectively. Two dysregulated pathways namely d-glutamine and D-glutamate metabolism, and alanine, aspartate and glutamate metabolism were significantly affected in the co-exposure while not in either of the single exposure. These findings provide new insights into the toxic effects of MPs on aquatic organisms, and further studies on combined effects of MPs and OCs are suggested to be conducted.

Black alder's (Alnus glutinosa L.) defense against polycyclic aromatic hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons (PAHs) are one of the most common groups of pollutants that have toxic and carcinogenic effects. Black alder trees (Alnus glutinosa L.) have been used to remediate contaminated soils from industrial pollutants and heavy metals; however, their usefulness for PAH remediation is unclear. In this study, we examined the response of seedlings from four alder half-sib families (genetic groups sharing the same mother but different fathers) to exposure to four PAHs-phenanthrene, pyrene, naphthalene, and fluoranthene-each at three concentrations. Plant growth parameters were evaluated, and concentration of secondary metabolites and antioxidant activity were measured. The results of the morphological parameters showed that in general, higher PAH concentrations had a more negative effect on tree vitality than lower concentrations (shoot growth reduction by up to 76%). Each half-sib family also exhibited distinct responses in total phenol content (TPC) when exposed to varying concentrations of pollutants, with reductions in TPC ranging from 4 to 52% across different genetic lineages. Enzyme activity also varied between families, pollutants, and their concentrations; for example, while phenanthrene generally increased glutathione S-transferase (GST) activity in the 13-99-1K and 38-61-7K half-sib families, it unexpectedly decreased GST levels by 23% and 29% in the seedlings of the 26-133-6K and 41-65-7K families, respectively, emphasizing the nuanced and divergent enzymatic responses observed in this study. Further secondary metabolite and antioxidant activity analysis revealed distinct variations in the way PAHs impact the defense mechanism of alder seedlings from different genetic groups-prioritizing either enzymatic or non-enzymatic systems. To sum up, analyzing the varying effects of PAHs on distinct half-sib families of alders can prove advantageous in identifying the most efficient black alder genetic families for phytoremediation purposes.

DNA-stable isotope probing and metagenomics reveal Fe(II) oxidation by core microflora in microoxic rhizospheric habitats to mitigate the accumulation of cadmium and phenanthrene in rice.

Rice rhizosphere soil-porewater microdomains exist within an iron (Fe)-rich microoxic habitat during paddy soil flooding. However, the response mechanisms of core microflora in this habitat to Fe(II)-oxidation-mediated cadmium (Cd) and phenanthrene (Phen) remain unclear. Using gel-stabilized gradient systems to replicate the microoxic conditions in the rice rhizosphere porewater, we found that microaerophilic rhizobacteria drove Fe(II) oxidation to yield iron oxides, thereby reducing the Cd and Phen contents in the rhizosphere porewater and rice (Cd and Phen decreased by 15.9%-78.0% and 10.1%-37.4%, respectively). However, co-exposure to Cd and Phen resulted in a greater reduction in the Cd uptake and a greater increase in the Phen uptake in rice as compared to those in the Cd or Phen treatments, possibly attributing to the cation-π interactions between Cd and Phen, as well as competition between the adsorption sites on the roots. The elevation of Cd-tolerant genes and Phen-degradation genes in biogenic cell-mineral aggregates unveiled the survival strategies of rhizobacteria with respect to Cd and Phen in the microoxic habitat. Potential Cd-tolerant rhizobacteria (e.g., Pandoraea and Comamonas) and Phen-degradation rhizobacteria (e.g., Pseudoxanthobacter) were identified through the DNA-SIP and 16S rRNA gene amplicon sequencing. Metagenomic analysis further confirmed that these core microbes harbor Cd-tolerant, Phen-degradation, and Fe(II) oxidation genes, supporting their metabolic potential for Cd and/or Phen in the microoxic habitat of the rice rhizosphere. These findings suggest the potential mechanism and ecological significance of core rhizospheric microbial-driven Fe(II) oxidation in mitigating the bioavailability of Cd and Phen in paddy soil during flooding.

High phenanthrene degrading efficiency by different microbial compositions construction.

Microbial remediation has become the most promising technical means for the remediation of polycyclic aromatic hydrocarbons (PAHs) non-point source contaminated soil due to its low cost of treatment, complete degradation of pollutants, and in-situ remediation. In this study, in order to demonstrate the phenanthrene degrading microbial diversity, phenanthrene was chosen as the representative of PAHs and strains capable of degrading phenanthrene were isolated and screened from the sedimentation sludge and the bottom sludge of oil tank trucks, and high throughput sequencing was used to check the dominant strains with a good degrading effect on phenanthrene. Results showed even more than 50% of phenanthrene was degraded in all samples, the composition of PAH-degrading bacteria was diverse, and different environments constructed different functional microbial groups, which resulted in the microbial adapting to the diversity of the environment. Finally, a series of bacterial species with phenanthrene-degrading functions such as Achromobacter, Pseudomonas, Pseudochelatococcus, Bosea was enriched after nine transferring process. Overall, our study offers value information for the enrichment of functional degrading microbes of phenanthrene or other pollutants that more concern should be paid in not only the degradation rate, but also the diversity variation of microbial community composition.

Fluorescence and Photophysical Properties of Anthracene and Phenanthrene in Water.

Polyaromatic hydrocarbons (PAHs) are widely spread pollutants in the environment, including soil and water. Anthracene (anth) and phenanthrene (phen) pose severe health impacts on human lives due to their carcinogenic nature by increasing cancer risk to the skin, lungs, and bladder. Fluorescence spectroscopy is a promising , efficient and straightforward tool for characterizing these trace PAHs in water. Therefore, the current work provides a detailed insight into the fluorescence properties of anth and phen in water. The fluorescence EEMs (excitation-emission matrices) of anth showed emissions at 380 nm, 400 nm, and 425 nm with single excitation at 250 nm, whereas phen showed two emissions < 380 nm, at 350 nm and 365 with single excitation at 250 nm. Then the theoretical EX/EM wavelengths were calculated by DFT and CIS-B3LYP for these compounds in water. The environmental effect of pH variation on fluorescence EEM shows a significant difference in fluorescence intensity without changing in peak locations, with highest fluorescence intensity at neutral pH than acidic and alkaline. Furthermore, the theoretical pH effect was described for the first time by simulating the protonated (+ 1), deprotonated (-1) and neutral molecules in water at the DFT level of theory. The variation in simulated oscillator strengths was similar in trend with the experimental fluorescence intensity of these compounds. The HOMO-LUMO were calculated to obtain the energy gap, molecular softness, molecular hardness, electronic potential and electrophilicity of anth and phen. To find the fluorophore contribution, the fluorescence of homogeneous mixture of both isomers was analyzed, which showed an enhanced fluorescence intensity of anth by 12-20%, whereas a decrease of 9-14% was observed in phen. This study describes that the fluorescence technique could be a fast and easy method to distinguish and identify PAHs isomers (anth and phen) in water.

Effects of biodegradable microplastics coexistence with biochars produced at low and high temperatures on bacterial community structure and phenanthrene degradation in soil.

The increasing use of biodegradable plastics may result in more serious pollution of microplastics which often coexist with biochar in soil, this will affect how organic pollutants move and transform in the soil. This work investigated the effect of biodegradable polybutylene adipate-co-terephthalate (PBAT) coexistence with biochars produced at temperatures of 400 and 700 °C (W4 and W7) on soil bacterial communities and phenanthrene degradation. The results showed that coexistence of PBAT and biochar paticles greatly boosted the relative abundance of Nocardioides while decreased the relative abundance of Sphingomonas as compared to soils with a single addition of PBAT or biochar. Changes in soil Eh values were the most influential factor in bacterial communities (more than 40% contribution). The degradation ratio of phenanthrene when PBAT coexisted with W7 (39.6 ± 3.6%) was not significantly different from the treatment with a single W7 addition (35.0 ± 2.3%, P＞0.05), and was related to phenanthrene degradation in the adsorbed state of W7 in soil. In contrast, the degradation ratio of phenanthrene in PBAT coexisting with W4 (35.1 ± 3.5%) was intermediate between that of single PBAT (49.8 ± 0.9%) and W4 (13.7 ± 5.8%) treatments. This was primarily due to changes in the experiment's initial bioavailable phenanthrene content. Furthermore, after the introduction of earthworms, phenanthrene degradation ratio in coexistence treatments were very similar to that described above in the absence of earthworms. Except for two treatments that contain W7, phenanthrene degradation ratio in the other treatments was increased by the presence of earthworms (up to 23%), which is related to the enhanced relative abundance of polycyclic aromatic hydrocarbon-degraders. Our findings indicated that PBAT coexistence with high-temperature or low-temperature biochar had a completely different impact on bacterial communities and phenanthrene degradation in soil.

Analysis of the Adsorption Behavior of Phenanthrene on Microplastics Based on Two-Dimensional Correlation Spectroscopy.

Microplastics (MPs), an emerging pollutant, widely co-occur with polycyclic aromatic hydrocarbons (PAHs) in the environment. Therefore, the interaction between MPs and PAHs has been the focus of much attention in recent years. In this study, three types of MPs, i.e., polypropylene, polystyrene, and poly(vinyl chloride), with the same main chain were selected as the adsorbents, with phenanthrene (PHE) as the representative PAHs. The adsorption mechanisms were explored from the perspective of the molecular spectral level using a combination of Fourier transform infrared spectroscopy (FT-IR) with a two-dimensional correlation technique. The adsorption kinetics results showed that the adsorption of PHE on the three MPs was dominated by chemisorption. However, the FT-IR analysis results indicated that no new covalent bond was created during the adsorption process. Based on the above research, a generalized two-dimensional (2D) correlation spectral technique was employed to investigate the sequence of functional group changes during the adsorption process for different MPs. Furthermore, the hybrid 2D correlation spectral technique explored the effect of side groups attached to the main chain molecules of MPs on adsorption. The results showed that for all three MPs, the functional groups in the side chain have a higher affinity for PHE, which is due to their higher hydrophobicity. This study provides a feasible way to analyze the adsorption of pollutants on MPs, and the results are important for understanding the adsorption interaction between PAHs and MPs in the aquatic environment.

Phenanthrene-Degrading and Nickel-Resistant Neorhizobium Strain Isolated from Hydrocarbon-Contaminated Rhizosphere of Medicago sativa L.

Pollutant degradation and heavy-metal resistance may be important features of the rhizobia, making them promising agents for environment cleanup biotechnology. The degradation of phenanthrene, a three-ring polycyclic aromatic hydrocarbon (PAH), by the rhizobial strain Rsf11 isolated from the oil-polluted rhizosphere of alfalfa and the influence of nickel ions on this process were studied. On the basis of whole-genome and polyphasic taxonomy, the bacterium Rsf11 represent a novel species of the genus Neorhizobium, so the name Neorhizobium phenanthreniclasticum sp. nov. was proposed. Analysis of phenanthrene degradation by the Rsf1 strain revealed 1-hydroxy-2-naphthoic acid as the key intermediate and the activity of two enzymes apparently involved in PAH degradation. It was also shown that the nickel resistance of Rsf11 was connected with the extracellular adsorption of metal by EPS. The joint presence of phenanthrene and nickel in the medium reduced the degradation of PAH by the microorganism, apparently due to the inhibition of microbial growth but not due to the inhibition of the activity of the PAH degradation enzymes. Genes potentially involved in PAH catabolism and nickel resistance were discovered in the microorganism studied. N. phenanthreniclasticum strain Rsf11 can be considered as a promising candidate for use in the bioremediation of mixed PAH-heavy-metal contamination.

Indole-3-acetic acid enhances the co-transport of proton and phenanthrene mediated by TaSAUR80-5A in wheat roots.

Polycyclic aromatic hydrocarbons (PAHs) are a type of organic pollution that can accumulate in crops and hazard human health. This study used phenanthrene (PHE) as a model PAH and employed hydroponic experiments to illustrate the role of indole-3-acetic acid (IAA) in the regulation of PHE accumulation in wheat roots. At optimal concentrations, wheat roots treated with PHE + IAA showed a 46.9% increase in PHE concentration, whereas treatment with PHE + P-chlorophenoxyisobutyric acid resulted in a 38.77% reduction. Transcriptome analysis identified TaSAUR80-5A as the crucial gene for IAA-enhancing PHE uptake. IAA increases plasma membrane H+-ATPase activity, promoting active transport of PHE via the PHE/H+ cotransport mechanism. These results provide not only the theoretical basis necessary to better understand the function of IAA in PAHs uptake and transport by staple crops, but also a strategy for controlling PAHs accumulation in staple crops and enhancing phytoremediation of PAH-contaminated environments.

Mechanistic insight into the effects of interaction between biochar and soil with different properties on phenanthrene sorption.

Soil composition varies considerably in nature, so it is vital to investigate the mechanism of the effect of various soil parameters on biochar sorption capacity. In this study, two biochars (W4 and W7) were derived from wheat straw at temperatures of 400 and 700 °C and were incubated with three different soils. Changes in biochar surface features by aging in the soils and the consequent impact on phenanthrene sorption were examined. The results showed that the effect of adding biochar on phenanthrene sorption capacity (Koc) varied by soil. When biochar was freshly mixed with soil, the Koc value in soil with higher clay content was more dramatically altered by biochar, which is due to clay particles adhering to the biochar surface. Moreover, the Koc value was significantly decreased by the addition of W4 but increased by the addition of W7 in general. After aging, most of the Koc value decreased. The greatest decrease in Koc value was observed in biochar and soil composed with the highest clay content for W4 (24-63%), as well as soil composed with the highest organic matter content for W7 (46-64%). This is because the surface polarity and micropores of biochar dropped the most rapidly in these mixes, resulting in a significant decrease in hydrophobic and pore-filling properties. The results revealed that the impact of biochar-soil interactions on phenanthrene sorption is related to not only biochar properties but also soil clay particles, soil organic matter content and pH. The findings of the study can be utilized to assess the efficacy of biochar application in soil remediation for various features.

Maternal exposure to phenanthrene induces testicular apoptosis and Sertoli cell dysfunction in F1 adult male mice: a histological and molecular study.

Objective: Phenanthrene, a polycyclic aromatic hydrocarbon, is found in abundance in environmental pollutants, food, and drinking water. This substance can accumulate in body tissues and exert harmful effects. Moreover, phenanthrene can cross the placental barrier, potentially impacting fetal development. We aimed to explore the impacts of maternal exposure to phenanthrene on testicular tissue and Sertoli cell function in F1 mice. Methods: Female rats with vaginal plugs were randomly assigned to one of three groups: control, sham, or phenanthrene. The control group received no intervention during pregnancy. In the sham and phenanthrene groups, corn oil and a phenanthrene solution, respectively, were administered via gavage once every 2 days. Offspring were separated by sex 21 days after birth. At 56 days postnatal, male F1 offspring were euthanized, and their testes were harvested for histological and molecular analyses. Results: Phenanthrene exposure was associated with a lower testicular weight and volume, a smaller diameter of the seminiferous tubules, and a relative thinning of the germinal epithelium. These changes were associated with increased cellular apoptosis, as shown by the upregulation of caspase 3 expression. Additionally, we observed an increase in vacuolization and residual bodies within the tissue. Conversely, the number of Sertoli cells and expression levels of Sox9, as well as the Ocln and Itgb1 genes, were found to be lowered. Conclusion: Maternal exposure to phenanthrene impacts both germ cells and Sertoli cells, disrupting their function and leading to fertility disorders in male F1 offspring mice.

Constituents from Dendrobium aphyllum: Bibenzyls, furfurals, phenanthrenes, and phenylpropanoids and their antioxidant and anti-inflammatory potentials.

Chemical investigation on the aqueous extract of Dendrobium aphyllum led to the isolation of thirty-one constituents with structures identified by analysis of the extensive spectroscopic data (1D/2D NMR, MS, UV, and ECD), including previously undescribed two bibenzyls, one furfural, and one phenolic acid, namely trigonopol D (1), trigonopol C (2), dendrofunan A (10), and 6-(4-hydroxy-3-methoxyphenyl)-3,6-dioxohexyl acetate (30), respectively, as well as twenty-seven known ones. Among them, there were one new natural product (11), seven compounds (6-7, 9, 12, 20, 28, 31) described from the genus Dendrobium for the first time, and fifteen compounds (8, 13-17, 19, 21-27, 29) isolated from D. aphyllum for the first time. Further, the antioxidant and anti-inflammatory potentials of fifteen compounds (4-5, 8, 11-12, 14-19, 22, 24, 26, and 29) with significant scavenging capacities against DPPH and hydroxyl radicals, and virtual docking activities inhibiting COX-2 and 5-LOX, respectively. Our study may draw the attention of medicinal plant taxonomists and supply potential quality markers for discrimination of D. aphyllum from other species in Dendrobium genus.

Biotic/abiotic transformation mechanisms of phenanthrene in iron-rich constructed wetland under redox fluctuation.

Iron-rich constructed wetlands (CWs) could promote phenanthrene bioremediation efficiently through biotic and abiotic pathways, which have gained increasing attention. However, the biotic/abiotic transformation mechanisms of trace organic contaminants in iron-rich CW are still ambiguous. Herein, three CWs (i.e., CW-A: Control; CW-B: Iron-rich CW, CW-C: Iron-rich CW + tidal flow) were constructed to investigate the transformation mechanisms of phenanthrene through Mössbauer spectroscopy and metagenomics. Results demonstrated CW-C achieved the highest phenanthrene removal (94.0 %) and bacterial toxicity reduction (92.1 %) due to the optimized degradation pathway, and subsequently achieved the safe transformation of phenanthrene. Surface-bound/low-crystalline iron regulated hydroxyl radical (·OH) production predominantly, and its utilization was promoted in CW-C, which also improved electron transfer capacity. The enhanced electron transfer capacity led to the enrichment of PAH-degrading microorganisms (e.g., Thauera) and keystone species (Sphingobacteriales bacterium 46-32) in CW-C. Additionally, the abundances of phenanthrene transformation (e.g., EC:1.14.12.-) and tricarboxylic-acid-cycle (e.g., EC:2.3.3.1) enzyme were up-regulated in CW-C. Further analysis indicated that the safe transformation of phenanthrene was mainly attributed to the combined effect of abiotic (·OH and surface-bound/low-crystalline iron) and biotic (microbial community and diversity) mechanisms in CW-C, which contributed similarly. Our study revealed the essential role of active iron in the safe transformation of phenanthrene, and was beneficial for enhanced performance of iron-rich CW.

Effect of Biofouling on the Sorption of Organic Contaminants by Microplastics.

Microplastics in the aquatic environment are susceptible to colonization by surrounding microorganisms, which form biofilms over the microplastic's surface. These biofilm-laden microplastics can then interact with a diverse array of contaminants. In the present study, biofilms were grown on microplastics in a laboratory setting using Pseudomonas aeruginosa as a model biofilm-forming bacterium for periods of 5 to 15 days. The sorption of three organic compounds representing different levels of hydrophobicity, namely methylene blue (MB), phenanthrol, and phenanthrene, was used to evaluate the effect of biofilm biomass on the adsorption of organic contaminants to microplastics. The sorption of MB and phenanthrol was found to increase with biofouling time, indicating affinity between these contaminants and the biofilm biomass on the particle. However, the presence of a biofilm did not influence the sorption of phenanthrene on the microplastics. These results suggest that the hydrophobicity of organic contaminants plays a major role in how biofouling of microplastics will influence contaminant sorption by microplastics. For some contaminants, biofilm can enhance the role of microplastics as contaminant vectors. These findings emphasize the need to understand the biomass load on environmental microplastics and the contaminants that associate with it for an accurate representation of the risk associated with microplastics in the environment. Environ Toxicol Chem 2024;43:1973-1981. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Phenanthrene-Induced Cytochrome P450 Genes and Phenanthrene Tolerance Associated with Arabidopsis thaliana CYP75B1 Gene.

Polycyclic aromatic hydrocarbons (PAHs) form an important group of organic pollutants due to their distribution in the environment and their carcinogenic and/or mutagenic effects. In order to identify at the molecular level some of the players in the biodegradation and tolerance response to PAHs in plants, we have phenotyped 32 Arabidopsis thaliana T-DNA mutant lines corresponding to 16 cytochrome P450 (CYP) genes that showed to be differentially expressed under contrasted stress conditions induced by phenanthrene, a 3-ring PAH. This screening has allowed us to identify CYP75B1 (At5g07990) T-DNA mutants as the only ones being sensitive to phenanthrene-induced stress, supporting that CYP75B1 protein is necessary for PAH tolerance. CYP75B1 codes for a 3'flavonol hydroxylase. CYP75B1 gene was heterologously expressed on yeast in order to investigate whether it affects the A. thaliana response to phenanthrene by participating in its metabolization. Heterologously-produced CYP75B1 enzyme shows to be catalytically efficient against its physiological substrates (e.g., naringenin) but unable to metabolize phenanthrene or 9-phenanthrenol. In contrast, CYP75B1 seems rather involved in phenanthrene tolerance as a crucial element by regulating concentration of antioxidants through the production of 3'-hydroxylated flavonoids such as quercetin and cyanidin. In particular, we report a highly increased generation of reactive oxygen species (H2O2 and singlet oxygen) in cyp75b1 mutants compared to control plants in response to phenanthrene treatment. Overall, CYP75B1 shows to play an important role in the response to the deleterious effects of phenanthrene exposure and this is related to oxidative stress sensitivity rather than metabolization.

Maternal exposure to polycyclic aromatic hydrocarbons during pregnancy and timing of pubertal onset in a longitudinal mother-child cohort in rural Bangladesh.

BACKGROUND: In experimental studies, several polycyclic aromatic hydrocarbons (PAHs) have shown endocrine disrupting properties, but very few epidemiological studies have examined their impact on pubertal development and results have been heterogenous. OBJECTIVE: To explore if maternal PAH exposure during pregnancy was associated with the offspring's timing of pubertal onset. METHODS: We studied 582 mother-daughter dyads originating from a population-based cohort in a rural setting in Bangladesh. Maternal urinary samples, collected in early pregnancy (on average, gestational week 8), were analyzed for monohydroxylated metabolites of phenanthrene (1-OH-Phe, Σ2-,3-OH-Phe, and 4-OH-Phe), fluorene (Σ2-,3-OH-Flu), and pyrene (1-OH-Pyr) using liquid chromatography with tandem mass spectrometry (LC-MS/MS). The girls were interviewed on two separate occasions concerning date of menarche, as well as breast and pubic hair development according to Tanner. Associations were assessed using Kaplan-Meier analysis and multivariable-adjusted Cox proportional hazards regression or ordered logistic regression. RESULTS: In early pregnancy, the mothers' median urinary concentrations of Σ1-,2-,3-,4-OH-Phe, Σ2-,3-OH-Flu, and 1-OH-Pyr were 3.25 ng/mL, 2.0 ng/mL, and 2.3 ng/mL respectively. At the second follow-up, 78 % of the girls had reached menarche, and the median age of menarche was 12.7 ± 0.81 years. Girls whose mothers belonged to the second and third quintiles of ΣOH-Phe metabolites had a higher rate of menarche, indicating a younger menarcheal age (HR 1.39; 95 % CI 1.04, 1.86, and HR 1.41; 95 % CI 1.05, 1.88, respectively), than girls of mothers in the lowest quintile. This trend was not observed in relation to either breast or pubic hair development. None of the other maternal urinary PAH metabolites or the sum of all thereof in early pregnancy were associated with age at menarche or pubertal stage. CONCLUSIONS: Indications of non-monotonic associations of prenatal phenanthrene exposure with the daughters' age of menarche were found, warranting further investigation.

Host-Guest Cocrystallization of Phenanthrene[2]arene Macrocycles Facilitating Structure Determination of Liquid Organic Molecules.

Single-crystal X-ray diffraction analysis has emerged as the most reliable method for determining the structures of organic molecules. However, numerous analytes, such as liquid organic molecules, pose challenges in crystallization, making their structures directly elusive via X-ray crystallography methods. Herein, we introduced the rapid cocrystallization of a macrocycle named phenanthrene[2]arene (PTA, host) with 15 liquid organic molecules (guests). The guest liquid organic molecules were successively cocrystallized with the aid of the PTA host. Moreover, the chemical structures of the liquid organic molecules could be determined through single-crystal X-ray diffraction analysis. PTA exhibited high adaptivity and was capable of encapsulating liquid organic molecules without forming covalent bonds or strong directional interactions. The results revealed that the adaptive crystals of PTA exhibited excellent cocrystallization capacity. Weak noncovalent interactions between the host and guest molecules were crucial for organizing the guests in an ordered pattern.

A new phenanthrene with a spirolactone ring from Dendrobium ochreatum.

Dendroochreatene (1), a new phenanthrene derivative with a spirolactone ring, was isolated from the whole Dendrobium ochreatum plant together with 11 known compounds (2-12). The structure of the new compound was elucidated spectroscopically and phenolic compounds were firstly reported from D. ochreatum. Moscatilin (4), major compound isolated from D. ochreatum, was found to be cytotoxic toward H460 lung-cancer cells, with an IC50 value of 147.3 ± 0.9 µM, while loddigesiinol C (7), C-α-methoxy derivative was inactive.