Microwave-accelerated heating technique in fabrication of silver nanoparticles using propolis extract: optimization and characterization

Silver nanoparticle (AgNPs) is known as a new generation of antibiotics with high bactericidal activity and resistance toward numerous bacteria strains. In the present study, AgNPs were synthesized using propolis extract and microwave heating technique. Results indicated that, the prepared hydroalcoholic propolis extract had brix, turbidity, total phenol content and antioxidant activity of 5.21° Bx, 1.75 % a.u., 82.52 mg/g (gallic acid) and 93.32 %, respectively. FTIR analysis also indicated that the prepared extract had several main functional groups such as hydroxyl, carboxyl, amide I, amin and esters, which those could act as reducing and stabilizing agents in fabrication of stable AgNPs. Furthermore, GC-MS analysis demonstrated that alpha-terpinene, coumaran, p-methoxycinnamic acid, dimethyl caffeic acid and pinostrobin chalcone were the main bioactive compounds of the prepared propolis extract. Results revealed that AgNPs with small particle size (86 nm) and polydespersity index (0.299), and high zeta potential (−23.34) values could be synthesized using 0.1 mL of the extract in combination to 9 mL silver nitrate (1 mM) under microwave heating for 30 s. TEM analysis demonstrated that spherical fabricated AgNPs had uniform particle size distribution with particle size of less than 100 nm. Finally, synthesized AgNps indicated higher bactericidal activity against Listeria monocytogenes and Escherichia coli, with obtained clear zone diameter of 22 and 19 mm, respectively.