Comparative Study of Machine Learning-Based QSAR Modeling of Anti-inflammatory Compounds from Durian Extraction

Quantitative structure–activity relationship (QSAR) analysis, an in silico methodology, offers enhanced efficiency and cost effectiveness in investigating anti-inflammatory activity. In this study, a comprehensive comparative analysis employing four machine learning algorithms (random forest (RF), gradient boosting regression (GBR), support vector regression (SVR), and artificial neural networks (ANNs)) was conducted to elucidate the activities of naturally derived compounds from durian extraction. The analysis was grounded in the exploration of structural attributes encompassing steric and electrostatic properties. Notably, the nonlinear SVR model, utilizing five key features, exhibited superior performance compared to the other models. It demonstrated exceptional predictive accuracy for both the training and external test datasets, yielding R2 values of 0.907 and 0.812, respectively; in addition, their RMSE resulted in 0.123 and 0.097, respectively. The study outcomes underscore the significance of specific structural factors (denoted as shadow ratio, dipole z, methyl, ellipsoidal volume, and methoxy) in determining anti-inflammatory efficacy. Thus, the findings highlight the potential of molecular simulations and machine learning as alternative avenues for the rational design of novel anti-inflammatory agents

Metal–Porphyrin: A Potential Catalyst for Direct Decomposition of N₂O by Theoretical Reaction Mechanism Investigation

The adsorption of nitrous oxide (N₂O) on metal–porphyrins (metal: Ti, Cr, Fe, Co, Ni, Cu, or Zn) has been theoretically investigated using density functional theory with the M06L functional to explore their use as potential catalysts for the direct decomposition of N₂O. Among these metal–porphyrins, Ti–porphyrin is the most active for N₂O adsorption in the triplet ground state with the strongest adsorption energy (−13.32 kcal/mol). Ti–porphyrin was then assessed for the direct decomposition of N₂O. For the overall reaction mechanism of three N₂O molecules on Ti–porphyrin, two plausible catalytic cycles are proposed. Cycle 1 involves the consecutive decomposition of the first two N₂O molecules, while cycle 2 is the decomposition of the third N₂O molecule. For cycle 1, the activation energies of the first and second N₂O decompositions are computed to be 3.77 and 49.99 kcal/mol, respectively. The activation energy for the third N₂O decomposition in cycle 2 is 47.79 kcal/mol, which is slightly lower than that of the second activation energy of the first cycle. O₂ molecules are released in cycles 1 and 2 as the products of the reaction, which requires endothermic energies of 102.96 and 3.63 kcal/mol, respectively. Therefore, the O₂ desorption is mainly released in catalytic cycle 2 of a TiO₃–porphyrin intermediate catalyst. In conclusion, regarding the O₂ desorption step for the direct decomposition of N₂O, the findings would be very useful to guide the search for potential N₂O decomposition catalysts in new directions

Excited-State Geometries of Heteroaromatic Compounds: A Comparative TD-DFT and SAC-CI Study

The structures of low-lying singlet excited states of nine π-conjugated heteroaromatic compounds have been investigated by the symmetry-adapted cluster-configuration interaction (SAC-CI) method and the time-dependent density functional theory (TDDFT) using the PBE0 functional (TD-PBE0). In particular, the geometry relaxation in some ππ* and nπ* excited states of furan, pyrrole, pyridine, <i>p</i>-benzoquinone, uracil, adenine, 9,10-anthraquinone, coumarin, and 1,8-naphthalimide as well as the corresponding vertical transitions, including Rydberg excited states, have been analyzed in detail. The basis set and functional dependence of the results was also examined. The SAC-CI and TD-PBE0 calculations showed reasonable agreement in both transition energies and excited-state equilibrium structures for these heteroaromatic compounds

Morphology-Dependent Properties of MnO_<i>x</i>/ZrO₂–CeO₂ Nanostructures for the Selective Catalytic Reduction of NO with NH₃

The morphology effect of ZrO₂–CeO₂ on the performance of MnO_<i>x</i>/ZrO₂–CeO₂ catalyst for the selective catalytic reduction of NO with ammonia was investigated. The catalytic tests showed that the MnO_<i>x</i>/ZrO₂–CeO₂ nanorods achieved significantly higher NO conversions than the nanocubes and nanopolyhedra. The catalytic tests also showed that the MnO_<i>x</i>/ZrO₂–CeO₂ nanorods achieved a significantly higher rate constant with respect to NO conversion than that of the nanocubes and nanopolyhedra. On the nanorods, the apparent activation energy is 25 kJ mol^–1, which was much lower than the values of nanocubes and nanopolyhedra (42 and 43 kJ mol^–1). The high resolution transmission electron microscopy showed that the nanorods predominately exposed {110} and {100} planes. It was demonstrated that the ZrO₂–CeO₂ nanorods had a strong interaction with MnO_<i>x</i> species, which resulted in great superiority for the selective catalytic reduction of NO. The excellent catalytic activity of the MnO_<i>x</i>/ZrO₂–CeO₂ nanorods should be attributed to the Mn⁴⁺ species, adsorbed surface oxygen and oxygen vacancies which are associated with their exposed {110} and {100} planes

Combination of Experimental and Theoretical Investigations of MnO_<i>x</i>/Ce_0.9Zr_0.1O₂ Nanorods for Selective Catalytic Reduction of NO with Ammonia

Manganese oxides (MnO_<i>x</i>) supported on Ce_0.9Zr_0.1O₂ (MnO_<i>x</i>/Ce_0.9Zr_0.1O₂) nanorods were synthesized and tested for low-temperature selective catalytic reduction of NO with ammonia. The catalysts were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction. The structure and morphology results show that the MnO_<i>x</i> was highly dispersed on the surface of Ce_0.9Zr_0.1O₂ nanorods. Various species, such as Mn²⁺, Mn³⁺, and Mn⁴⁺, were exposed due to a strong interaction between manganese and cerium oxides. Thus, the MnO_<i>x</i>/Ce_0.9Zr_0.1O₂ nanorods exhibited a better catalytic performance (90% NO conversion at 150 °C) compared with that of the as-prepared Ce_0.9Zr_0.1O₂ nanorods. Density functional theory (DFT) calculations clearly demonstrated that the MnO_<i>x</i> on the surface of supporting nanorods or Mn@CeO₂(110) could easily form an oxygen vacancy distortion. Furthermore, the Mn@CeO₂(110) model in the DFT analysis showed a prominent effect on the NO and NH₃ adsorption which resulted in a stronger nitrite intermediate (NOO*) formation and more attractive interaction with the NH₃ gas compared with those observed with the CeO₂(110) model. Therefore, a thorough understanding of the structure and catalytic performance of MnO_<i>x</i>/Ce_0.9Zr_0.1O₂ nanorods was successfully achieved by a combination of experimental and theoretical studies

Facet–Activity Relationship of TiO₂ in Fe₂O₃/TiO₂ Nanocatalysts for Selective Catalytic Reduction of NO with NH₃: <i>In Situ</i> DRIFTs and DFT Studies

Anatase TiO₂ nanosheets (TiO₂-NS) and nanospindles (TiO₂-NSP) have been successfully prepared with F^– and glacial acetic acid as structure-directing agents, respectively. The Fe₂O₃/TiO₂-NS and Fe₂O₃/TiO₂-NSP nanocatalysts were prepared by a wet incipient impregnation method with a monolayer amount of Fe₂O₃. All the catalysts were employed for the selective catalytic reduction of NO with NH₃ (NH₃-SCR) in order to understand the morphology-dependent effects. It is interesting that the Fe₂O₃/TiO₂-NS nanocatalyst exhibited better removal efficiency of NO_<i>x</i> in the temperature range of 100–450 °C, which was attributed to more oxygen defects and active oxygen, acid sites, as well as adsorbed nitrate species based on Raman spectra, XPS, NH₃-TPD, NO+O₂-TPD, and <i>in situ</i> DRIFTS. The density functional theory (DFT) method was used to clarify the NO and NH₃ adsorption abilities over the catalyst models of Fe₂O₃/TiO₂{001} and Fe₂O₃/TiO₂{101}. The results showed that the NH₃ adsorption energy over the TiO₂{001} (−2.00 eV) was lower than that over TiO₂{101} (−1.21 eV), and the NO adsorption energy over TiO₂{001} (−1.62 eV) was also lower than that over TiO₂{101} (−0.29 eV), which agreed well with the experimental results that Fe₂O₃/TiO₂-NS achieved higher catalytic activity than Fe₂O₃/TiO₂-NSP for NH₃-SCR of NO. In addition, the rapid electron transfer and regeneration of Fe³⁺ on the {001} facet of Fe₂O₃/TiO₂-NS also promoted the NH₃-SCR reaction efficiency. This work paves a way for understanding the facet–activity relationship of Fe₂O₃/TiO₂ nanocatalysts in the NH₃-SCR reaction