Synthesis, characterization, surface analysis, optical activity and solvent effects on the electronic absorptions of Schiff base-functionalized amino thiophene derivatives: Experimental and TD-DFT investigations

Isolation, characterization and evaluation of oxypeucedanin and osthol from local endemic Prangos aricakensis Behçet and Yapar root as antioxidant, enzyme inhibitory, antibacterial and DNA protection: molecular docking and DFT approaches

Prangos species were previously used against many disorders due to their chemical component. Prangos aricakensis Behçet & Yapar is a newly discovered local endemic species in Turkey's eastern region, and there is no research on P. aricakensis in the literature. In this work, oxypeucedanin and osthol molecules have been isolated from the root part of P. aricakensis for the first time. Oxypeucedanin and osthol structures were elucidated by 1D and 2D NMR analysis. For the bioactivities determination, antioxidant (DPPH· and ABTS·+ scavenging), enzyme inhibition (AChE, BChE, tyrosinase, and urease), antibacterial and DNA protection activity studies were applied for both molecules and compared with standard drug molecules, after applying enzyme kinetic assays and in silico approaches to clarify the mechanism of action for both molecules with enzymes, using molecular docking and density functional theory (DFT). Oxypeucedanin (2.19 ± 0.38 µg/mL) and osthol (4.57 ± 1.28 µg/mL) exhibited better activity than standards in DPPH∙ scavenging activity. Osthol (11.76 ± 0.59 µg/mL) showed a better tyrosinase inhibition effect than kojic acid (12.82 ± 0.91 µg/mL), and oxypeucedanin (3.03 ± 0.01 µg/mL) showed better urease inhibition effect than thiourea (5.37 ± 1.86 µg/mL). Our results showed that the osthol molecule was an excellent skin protective agent while the oxypeucedanin molecule could be a remarkable antiulcer agent. Therefore, although this study is the first in its field, it remained in the in vitro and in silico stages and is thought to pave the way for in vivo studies in the future.Communicated by Ramaswamy H. Sarma.

Solvent Influence on Absorption Spectra and Tautomeric Equilibria of Symmetric Azomethine-Functionalized Derivatives: Structural Elucidation and Computational Studies

A new series of azomethine‐functionalized compounds was synthesized from the condensation of 2‐hydroxy‐1,3‐propanediamine and 2‐thienylcarboxaldehydes in the presence of a drying agent. The derivatives were spectroscopically characterized by NMR, LC‐MS, UV/Vis, IR and elemental analysis. Variable temperature ¹H‐NMR (−60 to +60 °C) was performed to investigate the effect of solvent polarity; the capability of solvent to form H‐bond was found to dramatically influencing the tautomerization process of the desired structures. The calculated thermochemical parameters (ΔH₂₉₈, ΔG₂₉₈ and ΔS₂₉₈) at DFT and MP2 levels of theory explained that 3 b exists in equilibrium with two tautomers. The basis of the electronic absorptions was pursued through Time‐Dependent Density‐Functional Theory (TD‐DFT). Analysis of the structural surfaces was inspected and the molecular electrostatic potential (MEP) demonstrated that the three functionalized compounds were relatively analogous in the electronic distributions. Furthermore, the electrophilic and nucleophilic centers lying on the molecular surfaces were probably playing a key‐role in stabilizing the compounds through the nonclassical C−H⋅⋅⋅π interactions and hydrogen bonding. The impact of solvent polarity on absorption spectra were investigated via solvatochromic shifts. For instance, compound 3 c displayed a gradual shift of the maximum absorption to the red area when the solvent polarity was increased, recording a 21 nm of bathochromic shift. In contrast, no significant solvent‐effect on 3 a and 3 b was observed. The solvation relation was pursued between Gutmann's donicity numbers the experimental λ_max; exhibited almost positive linear performance with a minor oscillation, that ascribe to the possible weak interface between the molecules of solute and designated solvents. The bandgap energy of all products were assessed experimentally using optical absorption spectra following Tauc approach, giving −4.050 (3 a), −3.900 (3 b) and −3.210 (3 c) eV. However, the ΔE were computationally figured out from TD‐DFT simulation to be −4.258 (3 a), −4.022 (3 b) and −3.390 (3 c) eV.