Green synthesis of silver nanoparticles using mature-pseudostem extracts of Alpinia nigra and their bioactivities

Abstract

Green synthesis of silver nanoparticles (AgNPs) employing agricultural wastes as plant extracts to improve environmental benignity and also economic value added is the highlight of this research. The mature pseudostem of Alpinia nigra is an unbeneficial raw material discarded from several food ingredients and medicinal formulas. Therefore, this research focused on condition optimization for AgNP synthesis with ecofriendly techniques using A. nigra mature-pseudostem extracts and evaluation of their antioxidant, antibacterial activities, and toxicity with brine shrimp lethality assay (BSLA). The optimal reaction conditions were achieved by using 5 mM silver nitrate (AgNO3) solution with a volume ratio of 2:8 for the extract to AgNO3 at pH 12 under room temperature. The morphology and crystalline phase of the generated AgNPs were characterized using UV–visible spectrophotometry, field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray, X-ray diffraction, and Fourier transform-infrared (FTIR) techniques. The FE-SEM analysis exposed spherical shapes with an average diameter of approximately 49 nm. The XRD analysis indicated their face center cubic structure, and the FTIR spectra confirmed that phytochemicals from A. nigra extract promoted the synthesis of AgNPs. In particular, the biosynthesized AgNPs presented potential antibacterial activity against both Staphylococcus aureus and Escherichia coli and effective antioxidant capacity using the DPPH radical scavenging assay. Additionally, non-toxic desired AgNPs were confirmed with BSLA.

Keywords

• green synthesis
• silver nanoparticles
• alpinia nigra
• antibacterial
• antioxidant