Ultrasound-assisted extraction of antimicrobial compounds from Thymus daenensis and Silybum marianum: Antimicrobial activity with and without the presence of natural silver nanoparticles.

The present study is devoted to prepare a new antibacterial and antifungal agent based on in situ-synthesized silver nanoparticles at room temperature using Rosmarinus officinalis (R. officinalis) leaf extract. The Ag-NPs characterization by UV-visible, SEM, TEM and XRD revealed that the particles sizes were in the range of 10-33 nm. In this study, hydroalcoholic extracts were used with ultrasonic method. Ultrasonication has recently received attention as a novel bioprocessing tool for process intensification in many areas of downstream processing. The antimicrobial activities of T. daenensis and S. marianum extracts with and without the presence of Ag-NPs were investigated at concentrations from 12.5 to 50 mg/mL against Staphylococcus aureus (S. aureus, Gram-positive organism) and Escherichia coli (E. coli, Gram-negative organism), and fungal strains were Aspergillus oryzae (A. oryzae) and Candida albicans (C. albicans). Antimicrobial activity determined using agar disc diffusion method revealed that the activities of Ag-NPs/T. daenensis were superior to Ag-NPs/S. marianum and extracts (T. daenensis and S. marianum). The medicinal plant extract can be used to synthesize the Ag-NPs as an eco-friendly and inexpensive method in large scale. The results showed that the prepared Ag-NPs/extracts as good antibacterial and antifungal agents can be potentially applied against rapidly increasing of antibiotic resistance.