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.