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Hybrid Uracil Derivatives with Caffeine and Gramine Obtained via Click Chemistry as Potential Antioxidants and Inhibitors of Plant Pathogens
A series of novel hybrid uracil derivatives incorporating the natural alkaloids caffeine or gramine, linked via 1,2,3-triazole ring, were synthetized using click chemistry. The structures of the obtained compounds were confirmed by spectroscopic methods, including 1H NMR, 13C NMR, FT-IR, and mass spectrometry. The biological activity of hybrids was evaluated in vitro, including assessments of hemolytic activity, antioxidant potential, antifungal efficacy, and antibacterial activity. Additionally, molecular docking studies were conducted in silico for the most active antioxidant candidate. The results revealed that the hemocompatibility of the derivatives was structure-dependent. While caffeine-containing hybrids exhibited moderate-to-low cytoprotective activity under oxidative stress conditions, those incorporating gramine showed significantly higher potency. A plausible molecular mechanism underlying their cytoprotective activity is proposed. Several compounds also inhibited the growth of the plant pathogens Fusarium culmorum and Botrytis cinerea. The promising antioxidant and antifungal properties of selected uracil–alkaloid hybrids highlight their potential as multifunctional bioactive compounds for managing oxidative stress and controlling plant pathogens. Furthermore, the finding demonstrates the effectiveness of click chemistry as a versatile tool for the synthesis of bioactive heterocyclic compounds.
The Potential of Microwave Radiation and Mechanochemistry in the Formation of Purine Alkaloids Cocrystals Using Pyromellitic Acid as a Coformer: Synthesis, Structural, Spectroscopic, Thermal Analysis, and Biological Properties
Synthesis, Structure and Biological Activity of Indole-Imidazole Complexes with ZnCl2: Can Coordination Enhance the Functionality of Bioactive Ligands?
The ability of the indole–imidazole hybrid ligands to coordinate with the Zn(II) ion and the resulting structures of this new class of coordination compounds were analyzed in order to determine their structural properties and biological functionalities. For this purpose, six novel Zn(II) complexes, [Zn(InIm)2Cl2] (1), [Zn(InMeIm)2Cl2] (2), [Zn(IniPrIm)2Cl2] (3), [Zn(InEtMeIm)2Cl2] (4), [Zn(InPhIm)2Cl2] (5) and [Zn2(InBzIm)2Cl2] (6) (where InIm is 3-((1H-imidazol-1-yl)methyl)-1H-indole), were synthesized by the reactions of ZnCl2 and the corresponding ligand in a 1:2 molar ratio in methanol solvent at an ambient temperature. The structural and spectral characterization of these complexes was performed using NMR, FT–IR and ESI–MS spectrometry and elemental analysis, and the crystal structures of 1–5 were determined using single-crystal X-ray diffraction. Complexes 1–5 form polar supramolecular aggregates by utilizing, for this purpose, the N-H(indole)∙∙∙Cl(chloride) intermolecular hydrogen bonds. The assemblies thus formed differ depending on the distinctive molecular shape, which can be either compact or extended. All complexes were screened for their hemolytic, cytoprotective, antifungal, and antibacterial activities. The results show that the cytoprotective activity of the indole/imidazole ligand significantly increases upon its complexation with ZnCl2 up to a value comparable with the standard antioxidant Trolox, while the response of its substituted analogues is diverse and less pronounced.
Novel C3-Methylene-Bridged Indole Derivatives with and without Substituents at N1: The Influence of Substituents on Their Hemolytic, Cytoprotective, and Antimicrobial Activity
Alkaloids are natural compounds useful as scaffolds for discovering new bioactive molecules. This study utilized alkaloid gramine to synthesize two groups of C3-substituted indole derivatives, which were either functionalized at N1 or not. The compounds were characterized by spectroscopic methods. The protective effects of the new compounds against in vitro oxidative hemolysis induced by standard oxidant 2,2′-azobis(2-amidinopropane dihydro chloride (AAPH) on human erythrocytes as a cell model were investigated. Additionally, the compounds were screened for antimicrobial activity. The results indicated that most of the indole derivatives devoid of the N1 substitution exhibited strong cytoprotective properties. The docking studies supported the affinities of selected indole-based ligands as potential antioxidants. Furthermore, the derivatives obtained exhibited potent fungicidal properties. The structures of the eight derivatives possessing indole moiety bridged to the imidazole-, benzimidazole-, thiazole-, benzothiazole-, and 5-methylbenzothiazoline-2-thiones were determined by X-ray diffraction. The C=S bond lengths in the thioamide fragment pointed to the involvement of zwitterionic structures of varying contribution. The predominance of zwitterionic mesomers may explain the lack of cytoprotective properties, while steric effects, which limit multiple the hydrogen-bond acceptor properties of a thione sulfur, seem to be responsible for the high hemolytic activity.