Theoretical chemistry study on the toxicity of some polychlorobiphenyl (PCB) compounds using molecular descriptors

Toxicological assessment of photoactivated tetra-cationic porphyrin molecules under white light exposure in a Caenorhabditis elegans model

Photodynamic therapy (PDT) utilizes the potential of photosensitizing substances to absorb light energy and produce reactive oxygen species. Tetra-cationic porphyrins, which have organic or coordination compounds attached to their periphery, are heterocyclic derivatives with well-described antimicrobial and antitumoral properties. This is due to their ability to produce reactive oxygen species and their photobiological properties in solution. Consequently, these molecules are promising candidates as new and more effective photosensitizers with biomedical, environmental, and other biomedical applications. Prior to human exposure, it is essential to establish the toxicological profile of these molecules using in vivo models. In this study, we used Caenorhabditis elegans, a small free-living nematode, as a model for assessing toxic effects and predicting toxicity in preclinical research. We evaluated the toxic effects of porphyrins (neutral and tetra-cationic) on nematodes under dark/light conditions. Our findings demonstrate that tetra-methylated porphyrins (3TMeP and 4TMeP) at a concentration of 3.3 µg/mL (1.36 and 0.93 µM) exhibit high toxicity (as evidenced by reduced survival, development, and locomotion) under dark conditions. Moreover, photoactivated tetra-methylated porphyrins induce higher ROS levels compared to neutral (3TPyP and 4TPyP), tetra-palladated (3PdTPyP and 4PdTPyP), and tetra-platinated (3PtTPyP and 4PtTPyP) porphyrins, which may be responsible for the observed toxic effects.

Influence of molecular descriptors of plant volatilomics on fumigant action against the three major stored product beetle pests

Plant volatilomics such as essential oils (EOs) and volatile phytochemicals (PCs) are known as potential natural sources for the development of biofumigants as an alternative to conventional fumigant pesticides. This present work was aimed to evaluate the fumigant toxic effect of five selected EOs (cinnamon, garlic, lemon, orange, and peppermint) and PCs (citronellol, limonene, linalool, piperitone, and terpineol) against the Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum adults. Furthermore, for the estimation of the relationship between molecular descriptors and fumigant toxicity of plant volatiles, quantitative structural activity relationship (QSAR) models were developed using principal component analysis and multiple linear regression. Amongst the tested EOs, garlic EO was found to be the most toxic fumigant. The PCs toxicity analysis revealed that terpineol, limonene, linalool, and piperitone as potential fumigants to C. maculatus (< 20 µL/L air of LC50), limonene and piperitone as potential fumigants to T. castaneum (14.35 and 154.11 µL/L air of LC50, respectively), and linalool and piperitone as potential fumigants to S. oryzae (192.27 and 69.10 µL/L air of LC50, respectively). QSAR analysis demonstrated the role of various molecular descriptors of EOs and PCs on the fumigant toxicity in insect pest species. In specific, dipole and Randic index influence the toxicity in C. maculatus, molecular weight and maximal projection area influence the toxicity in S. oryzae, and boiling point and Dreiding energy influence the toxicity in T. castaneum. The present findings may provide insight of a new strategy to select effective EOs and/or PCs against stored product insect pests.

Theoretical and experimental studies on photocatalytic removal of methylene blue (MetB) from aqueous solution using oyster shell synthesized CaO nanoparticles (CaONP-O)

The development of technologies for the removal of dye from aqueous solution is most desirable if the end product is relatively green (i.e., environmentally friendly). Photodegradation (as one of such technology) and photolysis (without the catalyst) was applied to investigate the role of sol-gel synthesized calcium oxide nanoparticle (using the oyster shell as the precursor). The results obtained gave substantial evidence that calcium oxide nanoparticles catalyzed the degradation of the methylene blue dye up to a maximum percentage of 98 % removal. Degradation efficiency displayed a strong dependency on time, initial dye concentration, catalyst load, pH, and ionic strength. Chi-square and sum of square error analysis indicated that the photodegradation kinetics fitted the Langmuir-Hinshelwood, first order, and pseudo first-order models best. The half-life of the dye was significantly reduced from hours to minutes due to photocatalysis. Quantum chemical calculations indicated that the degradation proceeded through adsorption, deformation/degradation, and desorption through the chloride end of the molecule linked to the calcium active center of the catalyst. Results from Fukui functions and molecular descriptors analysis confirmed the mechanism of photocatalysis.

Quantum and experimental investigation of the application of Crassostrea gasar (mangrove oyster) shell-based CaO nanoparticles as adsorbent and photocatalyst for the removal of procaine penicillin from aqueous solution

The present study was designed to synthesize and characterize calcium oxide nanoparticles (using mangrove oyster shell as a precursor) and apply the synthesized nanoparticles as a photocatalyst to degrade procaine penicillin in an aqueous solution. The photocatalyst exhibited an average band gap of 4.42 eV, showed a maximum wavelength of absorbance in the UV region (i.e., 280 nm), and is a microporous nanoparticle with a particle diameter of 50 nm. The photocatalyzed degradation of the drug was conducted under natural sunlight, and the influence of parameters such as the period of contact, catalyst load, pH, initial drug concentration, and ionic strength was investigated concerning the degradation profile. The results obtained from response surface analysis indicated that an optimum degradation efficiency of about 93% can be obtained at a concentration, pH, and catalyst dosage of 0.125 M, 2, and 0.20 g respectively, at 0.902 desirabilities. The Langmuir-Hinshelwood, modified Freundlich, parabolic diffusion, pseudo-first-/second-order, and zero-, first-, and second-order kinetic parameters were tested to ascertain the best model that best described the experimental data. Consequently, the Langmuir-Hinshelwood, modified Freundlich, and pseudo-second-order models were accepted based on the minimum error and higher R2 values. Based on the Langmuir-Hinshelwood rate constants for adsorption and photodegradation as well as the evaluated valence bond potential, the degradation of the drug first proceeded through the mechanism of adsorption and followed by the oxidation of the drug by superoxide (generated from the interaction of electrons that generated by through the absorption of UV radiation). The quantum chemical calculation gave evidence that pointed towards the establishment of strong agreement with experimental data and also showed that the carboxyl functional group in the drug is the target site for adsorption and subsequent degradation.