Mycogenic TiO2 Nanoparticles Fabricated by Aspergillus niger: Room Temperature Green Synthesis of Bioactive 2-Amino-4H-1-benzopyrans

We report an environmentally friendly synthesis of titanium dioxide nanoparticles (TiO2 NPs) using titanium oxyhydroxide [TiO(OH)2] and the fungus strain Aspergillus niger isolated from a pond ecosystem. The mycogenic TiO2 NPs were characterized using FT-IR, XRD, FE-SEM, and TEM techniques. The Aspergillus niger-mediated TiO2 NPs functioned as an efficient, eco-friendly, and recyclable catalyst for the one-pot, three-component synthesis of 2-amino-4H-1-benzopyrans in aqueous medium at room temperature. A library of structurally diverse 2-amino-4H-1-benzopyran derivatives was thus synthesized and screened for antimicrobial activity against two bacterial strains (Escherichia coli and Bacillus subtilis) and two fungal strains (Aspergillus niger and Saccharomyces cerevisiae). Several compounds exhibited good to excellent antimicrobial activity. The developed protocol offers several notable advantages, including simple catalyst preparation, green reaction conditions, catalyst reusability, high yields, short reaction times, and easy purification.