Theoretical study of the molecular properties of dimethylanthracenes as properties for the prediction of their biodegradation and mutagenicity

Characterization of AhR-mediated potency in sediments from Kongsfjorden, Svalbard: Application of effect-directed analysis and nontarget screening

In this study, we aimed to identify the major aryl hydrocarbon receptor (AhR) agonists in surface sediments (S1-S10, n = 10) from Kongsfjorden, Arctic Svalbard, using effect-directed analysis. High AhR-mediated potencies were observed in the mid-polar fractions and RP-HPLC subfractions (F2.6-F2.8; log KOW 5-8) in the sediments of sites S2 and S3, which are located near abandoned coal mine areas, as assessed by the H4IIE-luc bioassay. The concentrations of traditional polycyclic aromatic hydrocarbon (t-PAHs), emerging PAHs, alkyl-PAHs, and styrene oligomers ranged from 6.1 to 2100 ng g-1 dry weight (dw), 0.5-1000 ng g-1 dw, 47 to 79,000 ng g-1 dw, and 4.2-130 ng g-1 dw, respectively, with elevated levels in S2 and S3. Principal component analysis coupled with multiple linear regression suggested that t-PAHs in sediments primarily originated from coal, petroleum combustion, and coal combustion. Twenty-four target AhR agonists accounted for 3.2%-100% (mean = 47%) of the total AhR-mediated potencies in S2 and S3. Nontarget screening via GC-QTOFMS in the highly potent fractions identified 48 AhR agonist candidates through four-step selection criteria. Among these, 27 compounds were identified as coal-derived substances. VirtualToxLab in silico modeling predicted that most of the 48 tentative AhR agonist candidates could bind to AhR. Overall, our findings indicate significant contamination of the Kongsfjorden sediments by coal-derived substances, highlighting the need for further studies to assess the ecological risks associated with these contaminants.

A novel procedure for selection of molecular descriptors: QSAR model for mutagenicity of nitroaromatic compounds

Nitroaromatic compounds (NACs) stand out as pervasive organic pollutants, prompting an imperative need to investigate their hazardous effects. Computational chemistry methods play a crucial role in this exploration, offering a safer and more time-efficient approach, mandated by various legislations. In this study, our focus lay on the development of transparent, interpretable, reproducible, and publicly available methodologies aimed at deriving quantitative structure-activity relationship models and testing them by modelling the mutagenicity of NACs against the Salmonella typhimurium TA100 strain. Descriptors were selected from Mordred and RDKit molecular descriptors, along with several quantum chemistry descriptors. For that purpose, the genetic algorithm (GA), as the most widely used method in the literature, and three alternative algorithms (Boruta, Featurewiz, and ForwardSelector) combined with the forward stepwise selection technique were used. The construction of models utilized the multiple linear regression method, with subsequent scrutiny of fitting and predictive performance, reliability, and robustness through various statistical validation criteria. The models were ranked by the Multi-Criteria Decision Making procedure. Findings have revealed that the proposed methodology for descriptor selection outperforms GA, with Featurewiz showing a slight advantage over Boruta and ForwardSelector. These constructed models can serve as valuable tools for the quick and reliable prediction of NACs mutagenicity.

Theoretical study of nitrodibenzofurans: A possible relationship between molecular properties and mutagenic activity

In this study we present a theoretical investigation of the molecular properties of nitrodibenzofurans (NDFs) and dinitrodibenzofurans (DNDFs) and their relation to mutagenic activity. Equilibrium geometries, relative energies, vertical ionization potentials (IP), vertical electron activities (EA), electronic dipole polarizabilities, and dipole moments of all NDFs and three DNDFs calculated by Density Functional Theory (DFT) methods are reported. The Ziegler/Rauk Energy Decomposition Analysis (EDA) is employed for a direct estimate of the variations of the orbital interaction and steric repulsion terms corresponding to the nitro group and the oxygen of the central ring of NDFs. The results indicate differences among NDF isomers for the cleavage of the related bonds and steric effects in the active site. The results show a good linear relationship between polarizability (<α>), anisotropy of polarizability (Δα), the summation of IR intensities (ΣIIR) and the summation of Raman activities (ΣARaman) over all 3N-6 vibrational modes and experimental mutagenic activities of NDF isomers in Salmonella typhimurium TA98 strain. The polarizability changes with respect to the νsNO+CN vibrational mode are in correlation with the mutagenic activities of NDFs and suggest that intermolecular interactions are favoured along this coordinate.

The Effects of Molecular Properties on Ready Biodegradation of Aromatic Compounds in the OECD 301B CO2 Evolution Test

Ready biodegradation is the primary biodegradability of a compound, which is used for discriminating whether a compound could be rapidly and readily biodegraded in the natural ecosystems in a short period and has been applied extensively in the environmental risk assessment of many chemicals. In this study, the effects of 24 molecular properties (including 2 physicochemical parameters, 10 geometrical parameters, 6 topological parameters, and 6 electronic parameters) on the ready biodegradation of 24 kinds of synthetic aromatic compounds were investigated using the OECD 301B CO2 Evolution test. The relationship between molecular properties and ready biodegradation of these aromatic compounds varied with molecular properties. A significant inverse correlation was found for the topological parameter TD, five geometrical parameters (Rad, CAA, CMA, CSEV, and N c), and the physicochemical parameter K ow, and a positive correlation for two topological parameters TC and TVC, whereas no significant correlation was observed for any of the electronic parameters. Based on the correlations between molecular properties and ready biodegradation of these aromatic compounds, the importance of molecular properties was demonstrated as follows: geometrical properties > topological properties > physicochemical properties > electronic properties. Our study first demonstrated the effects of molecular properties on ready biodegradation by a number of experiment data under the same experimental conditions, which should be taken into account to better guide the ready biodegradation tests and understand the mechanisms of the ready biodegradation of aromatic compounds.

Unexpected formation of N'-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester from acephate: chemical, biotechnical and computational study

By the nucleophilic attack of phenylhydrazine on acephate in aqueous medium, a stable product N′-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester (1) was obtained and characterized by elemental, spectral and thermal analysis. Thermodynamic parameters, Ea, ΔH°, ΔS° and ΔG°, have found to be 62.15, −67.95, −0.068 and −20.05 kJ mol⁻¹ according to the Coats–Redfern equation. Analysis of interaction of 1 with BSA protein was done by using the UV–Vis and FTIR spectroscopic methods. The observed binding constants was 1.12 (±0.09) × 10⁴ M⁻¹. The biological effect of 1 was checked on different plant growth-promoting (PGPR) strains such as Rhizobiumleguminosarum, Pseudomonasfluorescens, Arthrobactercitreus, Bacillusbrevis and Salmonellatyphimurium and compared with parent molecule acephate where 1 has shown less toxicity against PGPRs as compared to acephate. The experimental results for geometric parameters and values of peak position in IR spectra have found to match excellently with the computational studies performed by GAMESS software package. Theoretically, twelve new analogs of 1 were prepared and their comparative reactivity (HOMO–LUMO energy) and biodecomposition (on the basis of polarizability) is discussed.

Electronic properties of environmental pollutants and their mutagenic activity: Nitro derivatives of azaphenanthrenes

The physico-chemical properties of nitroazaphenanthrene isomers: 4-nitro-9-azaphenanthrene (4-N-9-Aph), 5-nitro-9-azaphenanthrene (5-N-9-Aph), 6-nitro-4-azaphenanthrene (6-N-4-Aph), 8-nitro-1-azaphenanthrene (8-N-1-Aph), and 8-nitro-4-azaphenanthrene (8-N-4-Aph) have been investigated theoretically using Density Functional Theory (DFT) calculations. Equilibrium geometries, relative stability, ionization potentials, electron affinities, molecular electrostatic potentials, dipole moments, electric polarizabilities, and vibrational properties of these isomers are presented. Averaged O-N-C-C dihedral angle, dipole moment, polarizability, the summation of IR intensities (∑IIR) and the summation of Raman activities (∑ARaman) over all 3N-6 vibrational degrees of freedom are sensitive to the structure of isomers. A very good linear relationship between ∑ARaman values (R=1.00) and the Salmonella typhimurium strain TA98(-S9) mutagenic activity of the investigated nitroazaphenanthrene isomers (Tokiwa et al., 2003) reveals a very important role of inductive and dispersive forces on the mutagenic pathways of the investigated isomers.

Two nitro derivatives of azabenzo[a]pyrene N-oxide: electronic properties and their relation to mutagenic activity

The equilibrium geometries, relative energies, IR and Raman spectra, vertical ionization potentials (IP), vertical electron affinities (EA), dipole moments (μ), electronic dipole polarizabilities (α), and molecular electrostatic potentials (MEP) of two species that show very high mutagenicity, 1-nitro-6-azabenzo[a]pyrene N-oxide (1-N-6-ABPO) and 3-nitro-6-azabenzo[a]pyrene N-oxide (3-N-6-ABPO), are investigated by means of Density Functional Theory (DFT) using B3LYP functional with different basis sets. The 3-N-6-ABPO isomer was estimated to be much more mutagenic in Salmonella typhimurium tester strain TA98 (396,000 revertants/nmol) than 1-N-6-ABPO (36100 revertants/nmol) (Fukuhara et al., 1992). The results show that for both isomers the structural, energetic, and vibrational properties are similar. The orientation of the nitro group with respect to the plane of the aromatic system as well as the nitroreduction and oxidation reaction and polarizability seem not be important for the determination of different mutagenic behavior of these isomers. However, the dipole moment of 3-N-6-ABPO is about 3 times that of 1-N-6-ABPO. The larger dipole moment and the different electronic charge distribution of 3-N-6-ABPO compared to 1-N-6-ABPO imply stronger electrostatic and inductive molecular interactions so that the active site of the enzyme involved in the mutagenic activation can more effectively bind 3-N-6-ABPO compared to 1-N-6-ABPO.