Biosynthesis of silver nanoparticles mediated by houttuynia cordata leaf extract: Characterization and improvement of anti-inflammatory activity

Abstract

Silver nanoparticles (Ag-NPs) were synthesized in an eco-friendly manner using aqueous Houttuynia cordata leaf extract (HLE). HLE mediated Ag-NPs (Ag-NPs/HLE) exhibited surface plasmon resonance with a maximum absorbance at 450 nm. The mean diameter of Ag-NPs was 23 nm, and their crystalline structure was confirmed via X-ray diffraction analysis. Fourier-transform infrared spectroscopy indicated that hydroxyl, carboxyl, and ketone groups of sugar or polyphenolics were involved in Ag-NPs synthesis. The contribution of reducing sugars to the reduction of Ag ions was found to be greater than that of polyphenols. NO production in LPS stimulated RAW 264.7 macrophages was more effectively inhibited by Ag-NPs/HLE than by chemically synthesized Ag-NPs. The production of the major inflammatory mediators, PGE2 and TNF-α was decreased by 73% and 66%, respectively, upon the addition of 10 μg/mL Ag-NPs/HLE. Ag-NPs biosynthesized using HLE showed improved anti-inflammatory activity compared to conventional Ag-NPs owing to the incorporation of phytochemicals.