Different types of honey on the synthesis of silver nanoparticles (AgNPs) and their antibacterial activity: In-vitro and in-silico studies

Abstract

AgNPs exhibit significant antibacterial activity, which is enhanced by their nanoscale size. Green synthesis using honey offers an eco-friendly, straightforward approach, with glucose and fructose in honey playing key roles in AgNPs synthesis. This study explores the effects of glucose and fructose concentrations in various honey types on AgNPs formation at 27–30 °C and pH 6–6.5, complemented by molecular docking studies. The sugar content in different honey samples was as follows: Cottonwood (56.66 %), Rambutan (49.95 %), Rubber (44.54 %), and Coffee (37.56 %). Higher bioreductor concentrations led to increased absorbance in the UV-Vis spectra; however, antibacterial activity decreased, albeit not significantly. This can be attributed to lower reducing sugar concentrations, which resulted in smaller AgNPs with a larger surface area, consequently affecting their antibacterial efficacy. The synthesized AgNPs were spherical (8–10 nm) and exhibited face-centered cubic crystallinity. The inhibition zones for AgNPs derived from cottonwood, rambutan, rubber, and coffee honey against Staphylococcus aureus were 14.51 mm, 14.54 mm, 15.45 mm, and 16.04 mm, respectively, and against Pseudomonas aeruginosa were 15.10 mm, 15.70 mm, 15.81 mm, and 15.90 mm, respectively. The microdilution broth assay revealed a sharp increase in antibacterial inhibition within the AgNPs concentration range of 5–50 ppm, plateauing above 50 ppm, with the steep increase halting between 20 and 40 ppm. MIC values ranged from 11.47 to 13.37 ppm for S. aureus and 8.71–10.62 ppm for P. aeruginosa. Molecular docking studies confirmed that D-glucose and D-fructose bind to bacterial proteins PBP2a and PBP3, supporting their role as bioreductors in AgNPs formation.