Launaea cornuta (wild lettuce) leaf extract: phytochemical analysis and synthesis of silver-zinc oxide nanocomposite

Abstract

Access to quality drinking water is an essential human right and a fundamental aspect of human dignity, yet a challenge to many in developing countries. Over 2 billion people worldwide lack access to quality drinking water due to microbial contamination, among other factors. Silver-doped zinc oxide impregnated activated carbon nanocomposites, Ag-ZnO-AC NCs, a strong antimicrobial agent have been used at point-of-use to treat water treatment. Green synthesis of Ag-ZnO-AC NCs has played a vital role since it leads to the acquisition of non-toxic nanocomposites compared to chemical synthesis. In this study, Ag-ZnO-AC NCs were green-synthesized using Launaea cornuta leaf extract as a source of reducing and capping agents in place of synthetic chemicals. Antioxidants from Launaea cornuta (Wild Lettuce) leaves were extracted using 0, 50, and 100% EtOH solvents with different volumes and extraction circles. The highest phenolic (11044 ± 63 μg) and antioxidant (44112 ± 894 μg) contents were extracted using 50% EtOH and 20 ml of extract solvent with p < 0.05. The SEM and TEM images of the synthesized Ag-ZnO-AC NCs show the formation of highly porous AC with sheet-like structures and successful Ag-ZnO NCs impregnation within the pores and on the surface of the AC. Based on the inhibition zone, the antimicrobial activity of the Ag-ZnO AC NCs had significant results with 14.00 ± 0.37 for E. coli and 17.33 ± 0.36 mm for S. aureus , p < 0.05. These results confirm the significance of Launaea cornuta (Wild Lettuce) as a source of antioxidants that can be used as reducing and capping agents to synthesize Ag-ZnO-AC NCs.

Keywords

• microbial inhibition
• phenolic content
• green synthesis
• reactive oxygen species (ROS)