Structural elucidation, theoretical insights and thermal properties of three novel multicomponent molecular forms of gallic acid with hydroxypyridines

Synthesis, spectroscopic, DFT calculations, biological activity, SAR, and molecular docking studies of novel bioactive pyridine derivatives

Enaminonitrile pyridine derivative was used as a precursor for preparation of fourteen heterocyclic compounds using both conventional thermal and microwave techniques. Diverse organic reagents, such as chloroacetyl chloride, acetic anhydride, chloroacetic acid, carbon disulfide, p-toluene sulfonyl chloride, maleic anhydride, phthalic anhydride, were used. The chemical formulae and structures of isolated derivatives were obtained using different analytical and spectroscopic techniques such as IR, 1H-, 13C-NMR as well as mass spectrometry. The spectroscopic analyses revealed diverse structure arrangements for the products. Molecular structure optimization of certain compounds were performed by the density functional theory (DFT/B3LYP) method and the basis set 6-31 G with double zeta plus polarization (d,p). The antimicrobial inhibition and the antioxidant activity of the reported compounds were screened. Compounds 5, 6, 11 and 13 exhibited the highest antibacterial inhibition, while compound 8 gave the highest scavenging activity (IC50 43.39 µg/ml) against the DPPH radical. Structure-activity relationship of the reported compounds were correlated with the data of antibacterial and the antioxidant activity. The global reactivity descriptors were also correlated with the biological properties of compounds. The molecular docking studies of reported compounds were investigated, and the analysis showed that the docked compounds have highly negative values for the functional binding scores. The binding interaction was found to be correlated with the substituent fragments of the compounds.

New Co-Crystals/Salts of Gallic Acid and Substituted Pyridines: An Effect of Ortho-Substituents on the Formation of an Acid–Pyridine Heterosynthon

Co-crystallization of gallic acid with pyridines and their polyaromatic analogue, quinoline, ortho-substituted by various proton-donating groups able to form hydrogen bonds, produced the only reported co-crystal of gallic acid with an ortho-substituted pyridine, 2-hydroxypyridine, as its preferred pyridone-2 tautomer, and four new crystalline products of gallic acid. These co-crystals, or gallate salts depending on the choice of the pyridine-containing compound, as predicted by the pKa rule, were identified by X-ray diffraction to feature the popular acid–pyridine heterosynthon found in most of the two-component systems of gallic acid that lack ortho-substituents in the pyridine-containing compound. This single-point heterosynthon is, however, modified by one or two proton-donating ortho-substituents, which sometimes may transform into the proton acceptors in an adopted tautomer or zwitterion, to produce its two- or other multi-point variants, including a very rare four-point heterosynthon. The hydrogen bonds they form with the gallic acid species in the appropriate co-crystals/salts strongly favors the formation of the acid–pyridine heterosynthon over the acid–acid homosynthon. In the competitive conditions of multi-component systems, such a modification might be used to reduce supramolecular-synthon-based polymorphism to produce new pharmaceuticals and other crystalline materials with designed properties.

Design, synthesis, characterization, and antioxidant activity studies of novel thienyl-pyrazoles

In a sustained search for novel and effective antioxidants, a potential therapeutic leads against renal, and neurological disorders. Amongst the heterocycles, pyrazole and their derivatives have been extensively studied for their biological potencies, particularly to a larger extent for their antioxidant properties. Although many of pyrazole derivatives displayed antioxidant activities, still there is a need of developing efficient protocol for their synthesis, involving ecofriendly conditions, molecules of greater antioxidant efficacy and lesser toxicity, etc. In this context, the current study presents an amberlyst-15 catalysed efficient synthesis of 2-pyrazoline derivatives, 5(a-g) via (3 + 2) annulation of chalcones with phenylhydrazines. Structure proofs of new pyrazoles offered by spectral studies, and the molecular structure of compound 5d of the series by crystallographic studies, which revealed an intra molecular hydrogen bond interactions (C–H⋯N type), and stabilization by C–H...π and π---π molecular interactions. Of the series, compounds 5g and 5h show excellent DPPH (IC₅₀ = 0.245 ± 0.01, and 0.284 ± 0.02 μM); and hydroxyl (IC₅₀ = 0.905 ± 0.01, and 0.892 ± 0.01μM) radical scavenging activities comparable with respective controls, ascorbic acid (IC₅₀ = 0.483 ± 0.01μM) and BHA (IC₅₀ = 1.739 ± 0.01μM). The molecular docking and ADME/Tox studies indicate that, these compounds have good antioxidant activity through π-π stacking with Catalase via Try337 and Phe140, and therefore, might be lead antioxidants for further study.

Preparation and solid-state characterization of dapsone pharmaceutical cocrystals through the supramolecular synthon strategy

Based on the design concept of supramolecular synthons, “–NH2⋯Npyridine” was used to prepare cocrystals of DAP: (1 : 1) and (2 : 1) DAP-PYR, which could be transformed into each other by mechanochemistry.

Design and synthesis of coumarin-triazole hybrids: biocompatible anti-diabetic agents, in silico molecular docking and ADME screening

The current study demonstrates the synthesis of coumarin-triazole hybrids 8 (a-e) in four steps starting from substituted salicylaldehyde 1 (a-e), and diethyl malonate 2. The spectroscopic studies provide the structure proofs of the new compounds, and the molecular structure of an intermediate 3a by crystallographic studies. The crystal structure analysis revealed the C–H...O, C–H... π, C–O...π and π...π molecular interactions. Further, the intermolecular interactions were quantified using Hirshfeld surface analysis and the DFT method B3LYP functional with 6–311++ G (d,p) basis set was employed to optimize the molecular geometry. The synthesized new coumarin-triazole hybrids, 8 (a–e) were screened for their α-amylase inhibitory potentials, and the results suggest that amongst the series, compounds 8c, and 8e show the promising inhibition of the enzyme, and might act as lead molecules for anti-diabetic activities. To understand the mode of action in silico molecular docking and ADME screening were performed.