Dual green synthesis of gold and silver nanoparticles mediated by citrus bee pollen extract: physicochemical and antibacterial insights

Abstract This study investigates the phenolic and sugar composition of an aqueous Syrian Citrus Bee Pollen (SCBP) extract and its application in the green synthesis of gold (AuNPs) and silver nanoparticles (AgNPs). High-performance liquid chromatography (HPLC) identified key phenolic compounds, including caffeic acid, cinnamic acid, kaempferol, apigenin, quercetin, and chrysin. The extract exhibited a high total sugar content (45.8 g/100 g), with total phenolic and flavonoid contents of 240.3 ± 0.04 mg GAE/g and 55.6 ± 0.03 mg QE/g, respectively. Experimental conditions were specifically set as follows: for AuNPs, SCBP extract 1%, HAuCl4·3H2O 2mM, pH 9.5, at room temperature; for AgNPs, SCBP extract 1%, AgNO3 2 mM, pH 10.5, at room temperature. AuNPs Formation was indicated by a purple color and a surface plasmon resonance (SPR) peak at 539 nm. Dynamic light scattering (DLS) analysis revealed a hydrodynamic size of 54.28 nm, a polydispersity index (PDI) of 0.144, and a zeta-potential (ζ) of − 26.9 mV. Field emission scanning electron microscopy (FESEM) showed spherical AuNPs with an average size of 36 nm. AgNPs showed a dark brown color with an SPR peak at 409 nm. DLS measurements indicated an average size of 54.33 nm, a PDI of 0.241, and a ζ-potential of − 25.5 mV. FESEM confirmed nearly spherical AgNPs averaging 49.9 nm with noticeable aggregation. Both nanoparticles showed promising antibacterial activity against S. aureus and S. epidermidis, with inhibition zones measuring 20 mm and 16 mm for AuNPs, and 13 mm and 11 mm for AgNPs, respectively. These findings demonstrate the potential of SCBP-mediated metal nanoparticles as eco-friendly, biocompatible antibacterial agents suitable for biomedical applications such as wound dressing and surface coating.