Synthesis and biological evaluation of new pyranopyridine derivatives catalyzed by guanidinium chloride-functionalized γ-Fe2O3/HAp magnetic nanoparticles

We, herein, describe the synthesis of hydroxyapatite-modified gamma-Fe2O3 magnetic nanoparticles grafted with guanidinium chloride and their characterization by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), transmission and scanning electron microscopy (TEM & SEM), and vibrating sample magnetometer (VSM) techniques. This newly developed nanocatalytic system has been explored as an efficient and recyclable nanocatalyst to effect the one-pot three-component condensation reactions of various aromatic aldehydes, malononitrile and 3-cyano-6-hydroxy-4-methylpyridin-2(1H)-one under solvent-free condition with excellent yields. The new pyranopyridine derivatives synthesized from this reaction were subjected to biological valuation as antioxidants by using an alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) free-radical scavenging assay and also for their antifungal capacity against the fungus Fusarium oxysporum. According to the experimental results, these products exhibit excellent antioxidant activity with an IC50 value of 0.140 +/- 0.003 to 0.751 +/- 0.008 mg mL(-1). In addition, these compounds exhibited reasonable antifungal activity against the Fusarium oxysporum fungus. In summary, the guanidinium chloride-functionalized magnetically hybrid nanocatalyst hydroxyapatite encapsulated gamma-Fe2O3 was found to be a quite excellent and recyclable catalytic system for the green synthesis of pyrano[2,3-b]pyridine derivatives having antioxidant and antifungal activities.