Eryngo Extract-Mediated Green Synthesis of Silver Nanoparticles and its Antibacterial Activity against Resistance Strains

In the present study, a simple and fast approach was developed for the green synthesis of silver nanoparticles by using Eryngium campestre (Eryngo) extract prepared in boiling water. People have widely used the Eryngo plant as a vegetable, food, and medicine around the world. The dried leaves of Eryngo extracted in boiling water yielded approximately 67 mg/g (6.6%) solid residue. The extract had a high antioxidant activity of 71 %, which was rich in total phenolic and flavonoids as revealed through colorimetric assays. For preparing nanoparticles, silver nitrate was added to the plant extract diluents and kept until the solution color changed with a sharp indicative peak of AgNPs that appeared at 450 nm. In addition, UV/Vis, TEM, FESEM, DLS, EDS, and XRD analysis were used to characterize the as-synthesized AgNPs. The results confirmed the spherical shape and nano nature of AgNPs with an average size of 32 nm based on Fe-SEM and TEM observations. The prepared AgNPs also shown moderate free radical scavenging activity (60%) in DPPH test and exhibit antibacterial activity at low concentration (50 μg/mL) toward both gram-positive and gram-negative bacteria. In this respect, the inhibition zone was higher in gram-positive bacteria and the sensitivity order of S.aureus > MRSA > B.subtilis > P.aeruginosa > E.coli was achieved in response to Eryngo AgNPs. Interestingly, Eryngo AgNPs at low concentration were efficient on MRSA, as an antibiotic-resistant strain of S.aureus.