Comparative evaluation of quercetin, rutin, and their nanoparticles: enhanced antimicrobial and antioxidant activities

Recent advances in nanoparticle (NP) technology have significantly improved the bioavailability and therapeutic efficacy of bioactive compounds. This study investigates the antimicrobial and antioxidant activities of quercetin and rutin in unprocessed (UP) and nanoparticle forms. Nanoparticles were prepared and characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Particle size analysis showed a substantial reduction, with rutin NPs measuring 98.76 nm compared to 181.7 nm (UP), and quercetin NPs measuring 91.28 nm compared to 185.8 nm (UP). Polydispersity index values 0.24 for rutin and 0.21 for quercetin indicated narrow size distribution and good homogeneity. Zeta potential values of − 28.6 mV (rutin) and − 30.2 mV (quercetin) confirmed adequate electrostatic stabilization and colloidal stability. SEM analysis revealed that NP formulations exhibited more uniform, smaller, and less crystalline morphology compared to UP forms, consistent with DLS findings. FTIR spectra confirmed the retention of characteristic functional groups, indicating no chemical modification and good compatibility. Furthermore, biological evaluation demonstrated significantly enhanced antimicrobial activity of NP formulations against bacterial strains, including Streptococcus pneumoniae, Bacillus subtilis, Staphylococcus aureus, Shigella flexneri, Pseudomonas aeruginosa, and Salmonella typhi, as well as fungal pathogens such as Trichophyton longifusas, Aspergillus flavus, Microsporum canis, Fusarium solani, Candida albicans, and Candida glabrata. Nanoparticles showed more zones of inhibition and lower minimum inhibitory concentrations compared to UP forms and standard drugs Cefazolin and Kanamycin (p-value < 0.01). In antioxidant assays, quercetin exhibited stronger activity than rutin. Overall, nanoformulations improved in vitro bioactivity.