Investigation of black seed honey: chemical properties and formation of antimicrobial silver nanoparticles

Abstract This study aimed to analyze the chemical composition of Syrian black seed honey, and then utilized its extract to synthesize silver nanoparticles (AgNPs), and assess their antimicrobial properties. The sugar content of the black seed honey showed fructose, glucose, and sucrose levels at 38.7 ± 1.50 g/100 g, 7.4 ± 2.13 g/100 g and 0.7 ± 0.20 g/100 g, respectively. Total phenolic content (TPC) and total flavonoid content (TFC) were measured at 263.3 ± 0.72 mg GAE /100 g, and 76.41 ± 1.20 mg QE /100 g, respectively. High-performance liquid chromatography (HPLC) confirmed the presence of six compounds: kaempferol, caffeic acid, cinnamic acid, apigenin, quercetin and chrysin. A concentrated solution of the honey, containing sugars, phenolics and flavonoids, was used to synthesize AgNPs, which were characterized using UV–Vis Spectroscopy, Dynamic Light Scattering (DLS) and Field Emission Scanning Electron Microscopy (FESEM). The AgNPs were well-dispersed and stable, with sizes ranging from 3 to 15 nm, with a polydispersity index (PDI) of 0.314 ± 0.02, and a ζ-potential of -21.7 mV according to DLS measurements. Microscopy and UV-Vis spectroscopy confirmed the formation of nanoparticles. The stable AgNPs were spherical with an average size of 26 nm according to FESEM, and the localized surface plasmon resonance (LSPR) peak in the UV-Vis Spectroscopy was observed at 415 nm. The antimicrobial activity of AgNPs was evaluated against Staphylococcus aureus , Staphylococcus epidermidis , Klebsiella spp., Escherichia coli , Pseudomonas aeruginosa , and Candida spp. The inhibition zones were (22 ± 0.28, 25 ± 0.41, 20 ± 0.33, 20 ± 0.27, 23 ± 0.43, and 20 ± 0.20 mm) respectively.