Biosynthesis of silver nanoparticles using oriental medicinal herb Gynostemma pentaphyllum Makino extract and their antibacterial activity against aquatic pathogen

The most promising strategies to overcome bacterial drug resistance are the use of nanoparticles (NPs). In this paper, the extract of Gynostemma pentaphyllum Makino was prepared and used as reducing as well as stabilising agent to obtain silver NPs (AgNPs). The active phytochemicals present in the herb were responsible for the quick reduction in silver ion (Ag+) to metallic AgNPs (Ag-0). The method is green and rapid, and the whole synthesis process can be finished within 15 min at 60 degrees C. An intense surface plasmon resonance band in 420-450 nm range clearly revealed the formation of AgNPs. The obtained AgNPs were further characterised using X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and zeta potential. Moreover, the as prepared AgNPs have a superior antibacterial activity against four kinds of aquatic pathogenic bacteria, which shows great potential in aquaculture field.